Engineering and Technology

2015 2(2) 23-34

Published online March 30 2015 (httpwwwaascitorgjournalet)

Keywords Heat Transfer

Integral - Fin Tube

Experimental Study

Received March 6 2015

Revised March 21 2015

Accepted March 22 2015

Heat Transfer Analysis of Integral-Fin Tubes

Laith Jaafer Habeeb1 Abdulhassan A Karamallah

1

Ayad Mezher Rahmah2

1Mech Eng Dept University of Technology Baghdad-Iraq 2State Company for Oil Projects (SCOP) Ministry of Oil Baghdad-Iraq

Email address laithhabeeb1974gmailcom (L J Habeeb) drlaith_jaaferuotechnologyeduiq (L J Habeeb)

Citation Laith Jaafer Habeeb Abdulhassan A Karamallah Ayad Mezher Rahmah Heat Transfer Analysis

of Integral-Fin Tubes Engineering and Technology Vol 2 No 2 2015 pp 23-34

Abstract An experimental system has been adapted to study the heat transfer characteristics for

cross flow air cooled single aluminum tube multi passes (smooth and integral low finned

tube) and the effect of the integral low fins in enhancement the heat transfer Also study

all variables which have effect on heat transfer phenomena A series of experiments was

conducted with different variables The velocities of air across the test section are (1 2

and 3) msec the water flow rate is (5lmin) and the temperatures of the inlet water to the

test tube are (50 60 70 80) oC In this study the integral low finned tube gave a good

enhancement in heat transfer Hence the experimental results showed that the air side

heat transfer coefficient of the integral low finned tube was higher than that of the

smooth tube and the enhancement ratio (( ho finned ho smooth ) or ( Nua finned Nua smooth )) was

(186 to 238) for eight passes Also the results showed that the increasing of air velocity

will improve the outside heat transfer coefficient In addition to the theoretical analysis

this work presents a suggestion to develop empirical correlations for the air side heat

transfer coefficient of an integral low finned tube represented by the empirical

correlations for the air side Nusselt number The results were compared with previous

works of other researchers and gave a good agreement in behavior

1 Introduction

One of the most common methods of enhanced heat transfer is by using integral low

fin tubes and the fins usually have a two-dimensional trapezoidal or rectangular cross

section [1] Integral finned tubes are made by extruding the fins from the tube metal The

tube is generally made from (copper aluminum and its alloys) that are relatively soft and

easily worked and also made of other materials (stainless steel titanium and its alloys

etc) [2 3] Since the fins are integral with the root tube perfect thermal contact is

ensured under any operating conditions [2] Integral fin tubes are commonly used in the

condensers of refrigeration air conditioning and process industries especially where low

surface tension fluids are used [4] It is also used in the heat exchanger evaporator and

boiling services [5] Fins are available in different densities ranging from 433ndash1675

finsmeter (11ndash40 finsinch) [3] In the last few decades several three dimensional (3D)

enhanced surfaces were developed for condensation heat exchangers Also several

improvements were introduced to the standard integral finned tubes which resulted in a

performance comparable to that of the 3D enhanced surfaces [4] Low fin heights are

ranging from about (066 to 150) mm depend on the fins density and the particular tube

metal [6]

Rich [7] performed an experimental work to determine the effect of fin spacing on

heat transfer and friction performance of multi-row fin-and-tube heat exchangers

24 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Later Rich [8] focused on the effect of the number of tube

rows on heat transfer performance of heat exchangers which

was a continuation of his previous experimental work

Brown [9] presented preliminary estimates for the thermal

design for heat exchangers He established a procedure in a

tabulated form for the design of heat exchanger with multi

rows of circular finned tubes

Wang et al [10] performed a comparison study of eight

finned-tube heat exchangers They concluded that the effect

of fin pitch on heat transfer performance is negligible for

four-row coils having ReDcgt 1000 and that for ReDclt 1000

the heat transfer performance is highly dependent on fin pitch

Haliciand Taymaz[11] investigated experimentally the

effect of tube regulation space on the heat and mass transfer

and friction factor for heat exchangers made from aluminum

fins and copper tubes

Chen and Hsu [12] studied theoretically and

experimentally the average heat transfer coefficient and fin

efficiency on a vertical annular circular fin of finned-tube

heat exchangers for various fin spacing in forced convection

Choi et al [13] investigated experimentally the heat

transfer characteristics of discrete plate finned-tube heat

exchangers with large fin pitches

Honda et al [14] investigated the theoretical model of film

condensation on a single horizontal low finned tube is

extended to include the effect of condensate inundation

Cheng et al [15] studied experimentally the condensation

heat transfer characteristics of horizontal enhanced tubes

Kumar et al [16] studied the heat transfer augmentation

during condensation of water and R-134a vapor on horizontal

integral-fin tubes In This experimental investigation was

performed on two different experimental set-ups for water

and R-134a

Tarrad [17] presented a computerized model for the

thermal-hydraulic design of a single shell ndash single pass low

finned tube bundle heat exchange using the step by step

technique (SST)

Fernaacutendez-Seara et al [18] investigated experimentally the

condensation of ammonia on smooth and integral-fin (32 fins

per inch (fpi)) titanium tubes of 1905mm outer diameter

In this investigation the effect of an integral low finned

tube in cross flow air cooled in a horizontal single tube multi

passes on the heat transfer behavior will be analyzed

experimentally and theoretically Also the effect of changing

air velocity and inlet water temperature are investigated This

work presents a suggestion to develop empirical correlations

for the air side heat transfer coefficient of an integral low

finned tube represented by the empirical correlations for the

air side Nusselt number

2 Experimental Work

21 The Test Rig

Figures (1- a b) show a photo and schematic diagram of

the experimental test rig The test rig is designed and

manufactured to fulfil the requirements of the test system for

a smooth and integral low finned tube The experimental

apparatus consist basically of

bull The duct and test section

bull The airflow rates supply section

bull The water flow rates supply section

bull The measuring devices

(a)

Engineering and Technology 2015 2(2) 23-34 25

(b)

Figure (1) Experimental test rig (a) Photo (b) Schematic diagram

22 Air Circulation System

The air was supplied to the test section by centrifugal

blower of (370 W) It was supplied air at three levels of

velocity (1 2 3) msec at the test section controlled by using

multi configurations of circular cross-section gate

manufactured for this purpose The gate controls air mass

flow rates and air velocities at the test section The required

velocities were obtained by replacing the configuration of the

gate between the fully opened without any gate (maximum

flow rate) and 45deg partially opened (minimum flow rate) The

blower outlet is connected directly to a galvanized steel air

diffuser by bolts after inserting the rubber seal and silicon

and the other side of diffuser is connected with the two layers

of the mesh at the face of the diffuser between the main duct

and diffuser The mesh is designed and manufactured to

ensure damping of any disturbance in air stream before

entering the test section and to obtain a regular flow

The air blower is fixed to the iron foundation by bolts with

thick rubber between the blower and foundation for damping

the vibration when the blower operates The duct is manufactured from a galvanized steel sheet at

rectangular cross section with width and height (251

mmtimes477mm) and length 2m with the test section part The

duct is connected with the blower by a diffuser and the other

side ended with another diffuser opened to the atmosphere

after insert the rubber seal and silicon at the edges The

suitable test duct length is 370 mm fixed at 2000 mm from

the beginning of inlet diffuser the test tube passed through

the duct horizontally at 2185mm from the beginning of inlet

diffuser as shown figure (2)

Figure (2) Schematic illustration of duct

26 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (3) (L) Photo of one of the test models (R) Section of integral low finned tube

23 Test Section

Two test sections were designed and manufactured in the

present work each one consists of rectangular test duct (251

times477 times350) mm width height and length respectively and

constructed from Perspex of (10 mm thickness) as shown in

figure(3-a) Each one has an aluminum test tube multi passes

passing horizontally through the test duct and the distance

between center to center of passes is 55mm the first test

section has a smooth aluminum tube of eight passes with

inner diameter 17mm and outer diameter 19mmThe second

test section has an integral low finned aluminum tube of eight

passes with inner diameter 17mm root diameter 19mm and

outer diameter at the tip of fin 22 mm Each pass has a length

251mm inside the duct with 125 fins which is approximately

(500 fins per meter)The finrsquos height is 15 mm with a

thickness of 1mm and pitch 1mm as shown in figure (3-

b)The finned tube was manufactured by the lathe machine

The test duct was connected to the main duct by aluminum

flanges and bolts and manufactured in a way for easy

replacement of the test section and inserting the rubber seal

and silicon at the connections The test pipe was connected to

the water cycle All the pipe bends outside the test duct were

fully insulated by a thermal rubber and insulating tape

24 Water Feeding System

A liquefied petroleum gas (LPG) water heater was used to

supply hot water quickly and continuously to the test section

The water outlet temperature can be controlled by a flame

adjustment knob and a water input adjusting knob

The other accessories used to complete the system are

Water pump of (370 W) with a maximum volumetric flow

rate (30 lmin) insulating tank of (30 L) capacity

manufactured from galvanized steel sheet and insulated by

(glass wool ) insulating pipes of 127mm (12 inch) diameter

manufactured from galvanized steel with valves and

connections insulated by (thermal rubber ) and iron structure

foundation to support all rig parts

25 The Measured Parameters

During the experimental investigation the main

parameters measured are

1) The inlet and outlet temperature of water at the test tube

2) The inlet and outlet pressure (pressure difference between

inlet and outlet of the test tube (3) The surface temperature

for the test tube 4) The water volumetric flow rate 5) The

temperature of air entering and leaving the test section 6)

The atmosphere temperature 7) The average air velocity

Digital anemometer and flow meter were used to measure

air velocities and water flow rates respectively and pressure

gauges were used to measure pressure drop in the water side

Multi thermocouples and temperature probes were used to

obtain the temperatures in inlet and outlet the test section at

water and air side respectively The thermal imager technique

(IR - fusion camera) was used to measure the surface

temperatures for the test tube All of these measuring devices

were used after the calibrating

26 Tests Procedure

The following procedure steps were conducted for each

experimental session after completing checking for the water

cycles and air system

1 Switch on the circuit breaker to supply power to the

whole system when all valves of the water cycle are

opened

2 Switch on the water heater by supply the liquefied

petroleum gas (LPG) to the heater

3 Adjust the air velocity regulated by using the gate at

one of the required three levels of air velocity

4 Adjust the water flow rate in water cycle by the

control valves of the water flow through main and

bypass pipes before the test tube or adjust by

controlling the input water flow rate adjusting knob

in the water heater at (5 lmin)

5 Adjust the required outlet temperature from the water

heater at inlet of the test section manually by

adjusting the knob of the flame or the knob of water

flow rate input to the heater

6 Watch the reading of water inlet and outlet

temperatures till the steady state conditions reached

(40-60) minutes Then take the following readings

7 Water temperatures for inlet and outlet of the test

tube b) Air temperatures for entering and leaving the

Engineering and Technology 2015 2(2) 23-34 27

test duct before and after the test tube c) The surface

temperature to the test tube by thermal imager d)

The atmospheric temperature e) The inlet and outlet

pressure (pressure drop in the test tube)

8 Repeat the experimental procedure for every case by

changing air velocity inlet water temperature and by

replacing the test sections (smooth and integral low

finned tube eight passes)

3 Theoretical Analysis

The first law of thermodynamics requires that the rate of

heat transfer from the hot fluid be equal to the rate of heat

transfer to the cold one or

= minus13 and

= 13 minus The rate of heat transfer in a heat exchanger can also be

expressed in the following form [2 19]

= ∆

For counter flow

∆ = ∆∆∆∆

= ∆∆∆∆n

∆ = 13 minus

∆ = minus 13 The actual logarithmic mean temperature difference of a

cross flow multi passes heat exchanger is obtained by [20

21]

∆ = ∆

then for cross flow

= ∆

The correction factor (Fcle 1) depends on the geometry of

the heat exchanger the inlet and outlet temperatures of the

hot and cold fluid streams number of tube rows and number

of passes The correction factor can be expressed as function

of the dimensionless ratios (R and S) given by [20 21]

= 13 minus minus 13

amp = ())) and

= + + 1ln 0102 minus 1 ln 3 0415+156 04155+1567

31 Water Side

The recommended correlation presented by [22] to predict

the heat transfer coefficient in a turbulent flow in tube is

89 = 0023gtABC

where Prandtl number index (n) is equal to (03) for cooling

process and this equation is valid for a turbulent flow with

(06 ltPrlt100) then the heat transfer coefficient equal to

ℎ13 = 0023gtEABC FEG13

where the Reynolds number based on the tube inside

diameter is

gtE =HE9EG13IE

or

gtE =GJKμE

where

K = EJ

13 = N4G13

and

AB = IEEPE

then

13 = 13Q∆

32 Air Side

The air side heat transfer coefficient general equation is

given in the form

For a smooth tube [19 22]

ℎ = 1R( minus

S([U(U) ] WX minus S()S)

And for an integral low finned tube [18]

ℎ = 1R( minus

S(Y[UZU) ] WX minus S(Y)S)

can be calculated using

1313Q = Q

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

24 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Later Rich [8] focused on the effect of the number of tube

rows on heat transfer performance of heat exchangers which

was a continuation of his previous experimental work

Brown [9] presented preliminary estimates for the thermal

design for heat exchangers He established a procedure in a

tabulated form for the design of heat exchanger with multi

rows of circular finned tubes

Wang et al [10] performed a comparison study of eight

finned-tube heat exchangers They concluded that the effect

of fin pitch on heat transfer performance is negligible for

four-row coils having ReDcgt 1000 and that for ReDclt 1000

the heat transfer performance is highly dependent on fin pitch

Haliciand Taymaz[11] investigated experimentally the

effect of tube regulation space on the heat and mass transfer

and friction factor for heat exchangers made from aluminum

fins and copper tubes

Chen and Hsu [12] studied theoretically and

experimentally the average heat transfer coefficient and fin

efficiency on a vertical annular circular fin of finned-tube

heat exchangers for various fin spacing in forced convection

Choi et al [13] investigated experimentally the heat

transfer characteristics of discrete plate finned-tube heat

exchangers with large fin pitches

Honda et al [14] investigated the theoretical model of film

condensation on a single horizontal low finned tube is

extended to include the effect of condensate inundation

Cheng et al [15] studied experimentally the condensation

heat transfer characteristics of horizontal enhanced tubes

Kumar et al [16] studied the heat transfer augmentation

during condensation of water and R-134a vapor on horizontal

integral-fin tubes In This experimental investigation was

performed on two different experimental set-ups for water

and R-134a

Tarrad [17] presented a computerized model for the

thermal-hydraulic design of a single shell ndash single pass low

finned tube bundle heat exchange using the step by step

technique (SST)

Fernaacutendez-Seara et al [18] investigated experimentally the

condensation of ammonia on smooth and integral-fin (32 fins

per inch (fpi)) titanium tubes of 1905mm outer diameter

In this investigation the effect of an integral low finned

tube in cross flow air cooled in a horizontal single tube multi

passes on the heat transfer behavior will be analyzed

experimentally and theoretically Also the effect of changing

air velocity and inlet water temperature are investigated This

work presents a suggestion to develop empirical correlations

for the air side heat transfer coefficient of an integral low

finned tube represented by the empirical correlations for the

air side Nusselt number

2 Experimental Work

21 The Test Rig

Figures (1- a b) show a photo and schematic diagram of

the experimental test rig The test rig is designed and

manufactured to fulfil the requirements of the test system for

a smooth and integral low finned tube The experimental

apparatus consist basically of

bull The duct and test section

bull The airflow rates supply section

bull The water flow rates supply section

bull The measuring devices

(a)

Engineering and Technology 2015 2(2) 23-34 25

(b)

Figure (1) Experimental test rig (a) Photo (b) Schematic diagram

22 Air Circulation System

The air was supplied to the test section by centrifugal

blower of (370 W) It was supplied air at three levels of

velocity (1 2 3) msec at the test section controlled by using

multi configurations of circular cross-section gate

manufactured for this purpose The gate controls air mass

flow rates and air velocities at the test section The required

velocities were obtained by replacing the configuration of the

gate between the fully opened without any gate (maximum

flow rate) and 45deg partially opened (minimum flow rate) The

blower outlet is connected directly to a galvanized steel air

diffuser by bolts after inserting the rubber seal and silicon

and the other side of diffuser is connected with the two layers

of the mesh at the face of the diffuser between the main duct

and diffuser The mesh is designed and manufactured to

ensure damping of any disturbance in air stream before

entering the test section and to obtain a regular flow

The air blower is fixed to the iron foundation by bolts with

thick rubber between the blower and foundation for damping

the vibration when the blower operates The duct is manufactured from a galvanized steel sheet at

rectangular cross section with width and height (251

mmtimes477mm) and length 2m with the test section part The

duct is connected with the blower by a diffuser and the other

side ended with another diffuser opened to the atmosphere

after insert the rubber seal and silicon at the edges The

suitable test duct length is 370 mm fixed at 2000 mm from

the beginning of inlet diffuser the test tube passed through

the duct horizontally at 2185mm from the beginning of inlet

diffuser as shown figure (2)

Figure (2) Schematic illustration of duct

26 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (3) (L) Photo of one of the test models (R) Section of integral low finned tube

23 Test Section

Two test sections were designed and manufactured in the

present work each one consists of rectangular test duct (251

times477 times350) mm width height and length respectively and

constructed from Perspex of (10 mm thickness) as shown in

figure(3-a) Each one has an aluminum test tube multi passes

passing horizontally through the test duct and the distance

between center to center of passes is 55mm the first test

section has a smooth aluminum tube of eight passes with

inner diameter 17mm and outer diameter 19mmThe second

test section has an integral low finned aluminum tube of eight

passes with inner diameter 17mm root diameter 19mm and

outer diameter at the tip of fin 22 mm Each pass has a length

251mm inside the duct with 125 fins which is approximately

(500 fins per meter)The finrsquos height is 15 mm with a

thickness of 1mm and pitch 1mm as shown in figure (3-

b)The finned tube was manufactured by the lathe machine

The test duct was connected to the main duct by aluminum

flanges and bolts and manufactured in a way for easy

replacement of the test section and inserting the rubber seal

and silicon at the connections The test pipe was connected to

the water cycle All the pipe bends outside the test duct were

fully insulated by a thermal rubber and insulating tape

24 Water Feeding System

A liquefied petroleum gas (LPG) water heater was used to

supply hot water quickly and continuously to the test section

The water outlet temperature can be controlled by a flame

adjustment knob and a water input adjusting knob

The other accessories used to complete the system are

Water pump of (370 W) with a maximum volumetric flow

rate (30 lmin) insulating tank of (30 L) capacity

manufactured from galvanized steel sheet and insulated by

(glass wool ) insulating pipes of 127mm (12 inch) diameter

manufactured from galvanized steel with valves and

connections insulated by (thermal rubber ) and iron structure

foundation to support all rig parts

25 The Measured Parameters

During the experimental investigation the main

parameters measured are

1) The inlet and outlet temperature of water at the test tube

2) The inlet and outlet pressure (pressure difference between

inlet and outlet of the test tube (3) The surface temperature

for the test tube 4) The water volumetric flow rate 5) The

temperature of air entering and leaving the test section 6)

The atmosphere temperature 7) The average air velocity

Digital anemometer and flow meter were used to measure

air velocities and water flow rates respectively and pressure

gauges were used to measure pressure drop in the water side

Multi thermocouples and temperature probes were used to

obtain the temperatures in inlet and outlet the test section at

water and air side respectively The thermal imager technique

(IR - fusion camera) was used to measure the surface

temperatures for the test tube All of these measuring devices

were used after the calibrating

26 Tests Procedure

The following procedure steps were conducted for each

experimental session after completing checking for the water

cycles and air system

1 Switch on the circuit breaker to supply power to the

whole system when all valves of the water cycle are

opened

2 Switch on the water heater by supply the liquefied

petroleum gas (LPG) to the heater

3 Adjust the air velocity regulated by using the gate at

one of the required three levels of air velocity

4 Adjust the water flow rate in water cycle by the

control valves of the water flow through main and

bypass pipes before the test tube or adjust by

controlling the input water flow rate adjusting knob

in the water heater at (5 lmin)

5 Adjust the required outlet temperature from the water

heater at inlet of the test section manually by

adjusting the knob of the flame or the knob of water

flow rate input to the heater

6 Watch the reading of water inlet and outlet

temperatures till the steady state conditions reached

(40-60) minutes Then take the following readings

7 Water temperatures for inlet and outlet of the test

tube b) Air temperatures for entering and leaving the

Engineering and Technology 2015 2(2) 23-34 27

test duct before and after the test tube c) The surface

temperature to the test tube by thermal imager d)

The atmospheric temperature e) The inlet and outlet

pressure (pressure drop in the test tube)

8 Repeat the experimental procedure for every case by

changing air velocity inlet water temperature and by

replacing the test sections (smooth and integral low

finned tube eight passes)

3 Theoretical Analysis

The first law of thermodynamics requires that the rate of

heat transfer from the hot fluid be equal to the rate of heat

transfer to the cold one or

= minus13 and

= 13 minus The rate of heat transfer in a heat exchanger can also be

expressed in the following form [2 19]

= ∆

For counter flow

∆ = ∆∆∆∆

= ∆∆∆∆n

∆ = 13 minus

∆ = minus 13 The actual logarithmic mean temperature difference of a

cross flow multi passes heat exchanger is obtained by [20

21]

∆ = ∆

then for cross flow

= ∆

The correction factor (Fcle 1) depends on the geometry of

the heat exchanger the inlet and outlet temperatures of the

hot and cold fluid streams number of tube rows and number

of passes The correction factor can be expressed as function

of the dimensionless ratios (R and S) given by [20 21]

= 13 minus minus 13

amp = ())) and

= + + 1ln 0102 minus 1 ln 3 0415+156 04155+1567

31 Water Side

The recommended correlation presented by [22] to predict

the heat transfer coefficient in a turbulent flow in tube is

89 = 0023gtABC

where Prandtl number index (n) is equal to (03) for cooling

process and this equation is valid for a turbulent flow with

(06 ltPrlt100) then the heat transfer coefficient equal to

ℎ13 = 0023gtEABC FEG13

where the Reynolds number based on the tube inside

diameter is

gtE =HE9EG13IE

or

gtE =GJKμE

where

K = EJ

13 = N4G13

and

AB = IEEPE

then

13 = 13Q∆

32 Air Side

The air side heat transfer coefficient general equation is

given in the form

For a smooth tube [19 22]

ℎ = 1R( minus

S([U(U) ] WX minus S()S)

And for an integral low finned tube [18]

ℎ = 1R( minus

S(Y[UZU) ] WX minus S(Y)S)

can be calculated using

1313Q = Q

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

Engineering and Technology 2015 2(2) 23-34 25

(b)

Figure (1) Experimental test rig (a) Photo (b) Schematic diagram

22 Air Circulation System

The air was supplied to the test section by centrifugal

blower of (370 W) It was supplied air at three levels of

velocity (1 2 3) msec at the test section controlled by using

multi configurations of circular cross-section gate

manufactured for this purpose The gate controls air mass

flow rates and air velocities at the test section The required

velocities were obtained by replacing the configuration of the

gate between the fully opened without any gate (maximum

flow rate) and 45deg partially opened (minimum flow rate) The

blower outlet is connected directly to a galvanized steel air

diffuser by bolts after inserting the rubber seal and silicon

and the other side of diffuser is connected with the two layers

of the mesh at the face of the diffuser between the main duct

and diffuser The mesh is designed and manufactured to

ensure damping of any disturbance in air stream before

entering the test section and to obtain a regular flow

The air blower is fixed to the iron foundation by bolts with

thick rubber between the blower and foundation for damping

the vibration when the blower operates The duct is manufactured from a galvanized steel sheet at

rectangular cross section with width and height (251

mmtimes477mm) and length 2m with the test section part The

duct is connected with the blower by a diffuser and the other

side ended with another diffuser opened to the atmosphere

after insert the rubber seal and silicon at the edges The

suitable test duct length is 370 mm fixed at 2000 mm from

the beginning of inlet diffuser the test tube passed through

the duct horizontally at 2185mm from the beginning of inlet

diffuser as shown figure (2)

Figure (2) Schematic illustration of duct

26 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (3) (L) Photo of one of the test models (R) Section of integral low finned tube

23 Test Section

Two test sections were designed and manufactured in the

present work each one consists of rectangular test duct (251

times477 times350) mm width height and length respectively and

constructed from Perspex of (10 mm thickness) as shown in

figure(3-a) Each one has an aluminum test tube multi passes

passing horizontally through the test duct and the distance

between center to center of passes is 55mm the first test

section has a smooth aluminum tube of eight passes with

inner diameter 17mm and outer diameter 19mmThe second

test section has an integral low finned aluminum tube of eight

passes with inner diameter 17mm root diameter 19mm and

outer diameter at the tip of fin 22 mm Each pass has a length

251mm inside the duct with 125 fins which is approximately

(500 fins per meter)The finrsquos height is 15 mm with a

thickness of 1mm and pitch 1mm as shown in figure (3-

b)The finned tube was manufactured by the lathe machine

The test duct was connected to the main duct by aluminum

flanges and bolts and manufactured in a way for easy

replacement of the test section and inserting the rubber seal

and silicon at the connections The test pipe was connected to

the water cycle All the pipe bends outside the test duct were

fully insulated by a thermal rubber and insulating tape

24 Water Feeding System

A liquefied petroleum gas (LPG) water heater was used to

supply hot water quickly and continuously to the test section

The water outlet temperature can be controlled by a flame

adjustment knob and a water input adjusting knob

The other accessories used to complete the system are

Water pump of (370 W) with a maximum volumetric flow

rate (30 lmin) insulating tank of (30 L) capacity

manufactured from galvanized steel sheet and insulated by

(glass wool ) insulating pipes of 127mm (12 inch) diameter

manufactured from galvanized steel with valves and

connections insulated by (thermal rubber ) and iron structure

foundation to support all rig parts

25 The Measured Parameters

During the experimental investigation the main

parameters measured are

1) The inlet and outlet temperature of water at the test tube

2) The inlet and outlet pressure (pressure difference between

inlet and outlet of the test tube (3) The surface temperature

for the test tube 4) The water volumetric flow rate 5) The

temperature of air entering and leaving the test section 6)

The atmosphere temperature 7) The average air velocity

Digital anemometer and flow meter were used to measure

air velocities and water flow rates respectively and pressure

gauges were used to measure pressure drop in the water side

Multi thermocouples and temperature probes were used to

obtain the temperatures in inlet and outlet the test section at

water and air side respectively The thermal imager technique

(IR - fusion camera) was used to measure the surface

temperatures for the test tube All of these measuring devices

were used after the calibrating

26 Tests Procedure

The following procedure steps were conducted for each

experimental session after completing checking for the water

cycles and air system

1 Switch on the circuit breaker to supply power to the

whole system when all valves of the water cycle are

opened

2 Switch on the water heater by supply the liquefied

petroleum gas (LPG) to the heater

3 Adjust the air velocity regulated by using the gate at

one of the required three levels of air velocity

4 Adjust the water flow rate in water cycle by the

control valves of the water flow through main and

bypass pipes before the test tube or adjust by

controlling the input water flow rate adjusting knob

in the water heater at (5 lmin)

5 Adjust the required outlet temperature from the water

heater at inlet of the test section manually by

adjusting the knob of the flame or the knob of water

flow rate input to the heater

6 Watch the reading of water inlet and outlet

temperatures till the steady state conditions reached

(40-60) minutes Then take the following readings

7 Water temperatures for inlet and outlet of the test

tube b) Air temperatures for entering and leaving the

Engineering and Technology 2015 2(2) 23-34 27

test duct before and after the test tube c) The surface

temperature to the test tube by thermal imager d)

The atmospheric temperature e) The inlet and outlet

pressure (pressure drop in the test tube)

8 Repeat the experimental procedure for every case by

changing air velocity inlet water temperature and by

replacing the test sections (smooth and integral low

finned tube eight passes)

3 Theoretical Analysis

The first law of thermodynamics requires that the rate of

heat transfer from the hot fluid be equal to the rate of heat

transfer to the cold one or

= minus13 and

= 13 minus The rate of heat transfer in a heat exchanger can also be

expressed in the following form [2 19]

= ∆

For counter flow

∆ = ∆∆∆∆

= ∆∆∆∆n

∆ = 13 minus

∆ = minus 13 The actual logarithmic mean temperature difference of a

cross flow multi passes heat exchanger is obtained by [20

21]

∆ = ∆

then for cross flow

= ∆

The correction factor (Fcle 1) depends on the geometry of

the heat exchanger the inlet and outlet temperatures of the

hot and cold fluid streams number of tube rows and number

of passes The correction factor can be expressed as function

of the dimensionless ratios (R and S) given by [20 21]

= 13 minus minus 13

amp = ())) and

= + + 1ln 0102 minus 1 ln 3 0415+156 04155+1567

31 Water Side

The recommended correlation presented by [22] to predict

the heat transfer coefficient in a turbulent flow in tube is

89 = 0023gtABC

where Prandtl number index (n) is equal to (03) for cooling

process and this equation is valid for a turbulent flow with

(06 ltPrlt100) then the heat transfer coefficient equal to

ℎ13 = 0023gtEABC FEG13

where the Reynolds number based on the tube inside

diameter is

gtE =HE9EG13IE

or

gtE =GJKμE

where

K = EJ

13 = N4G13

and

AB = IEEPE

then

13 = 13Q∆

32 Air Side

The air side heat transfer coefficient general equation is

given in the form

For a smooth tube [19 22]

ℎ = 1R( minus

S([U(U) ] WX minus S()S)

And for an integral low finned tube [18]

ℎ = 1R( minus

S(Y[UZU) ] WX minus S(Y)S)

can be calculated using

1313Q = Q

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

26 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (3) (L) Photo of one of the test models (R) Section of integral low finned tube

23 Test Section

Two test sections were designed and manufactured in the

present work each one consists of rectangular test duct (251

times477 times350) mm width height and length respectively and

constructed from Perspex of (10 mm thickness) as shown in

figure(3-a) Each one has an aluminum test tube multi passes

passing horizontally through the test duct and the distance

between center to center of passes is 55mm the first test

section has a smooth aluminum tube of eight passes with

inner diameter 17mm and outer diameter 19mmThe second

test section has an integral low finned aluminum tube of eight

passes with inner diameter 17mm root diameter 19mm and

outer diameter at the tip of fin 22 mm Each pass has a length

251mm inside the duct with 125 fins which is approximately

(500 fins per meter)The finrsquos height is 15 mm with a

thickness of 1mm and pitch 1mm as shown in figure (3-

b)The finned tube was manufactured by the lathe machine

The test duct was connected to the main duct by aluminum

flanges and bolts and manufactured in a way for easy

replacement of the test section and inserting the rubber seal

and silicon at the connections The test pipe was connected to

the water cycle All the pipe bends outside the test duct were

fully insulated by a thermal rubber and insulating tape

24 Water Feeding System

A liquefied petroleum gas (LPG) water heater was used to

supply hot water quickly and continuously to the test section

The water outlet temperature can be controlled by a flame

adjustment knob and a water input adjusting knob

The other accessories used to complete the system are

Water pump of (370 W) with a maximum volumetric flow

rate (30 lmin) insulating tank of (30 L) capacity

manufactured from galvanized steel sheet and insulated by

(glass wool ) insulating pipes of 127mm (12 inch) diameter

manufactured from galvanized steel with valves and

connections insulated by (thermal rubber ) and iron structure

foundation to support all rig parts

25 The Measured Parameters

During the experimental investigation the main

parameters measured are

1) The inlet and outlet temperature of water at the test tube

2) The inlet and outlet pressure (pressure difference between

inlet and outlet of the test tube (3) The surface temperature

for the test tube 4) The water volumetric flow rate 5) The

temperature of air entering and leaving the test section 6)

The atmosphere temperature 7) The average air velocity

Digital anemometer and flow meter were used to measure

air velocities and water flow rates respectively and pressure

gauges were used to measure pressure drop in the water side

Multi thermocouples and temperature probes were used to

obtain the temperatures in inlet and outlet the test section at

water and air side respectively The thermal imager technique

(IR - fusion camera) was used to measure the surface

temperatures for the test tube All of these measuring devices

were used after the calibrating

26 Tests Procedure

The following procedure steps were conducted for each

experimental session after completing checking for the water

cycles and air system

1 Switch on the circuit breaker to supply power to the

whole system when all valves of the water cycle are

opened

2 Switch on the water heater by supply the liquefied

petroleum gas (LPG) to the heater

3 Adjust the air velocity regulated by using the gate at

one of the required three levels of air velocity

4 Adjust the water flow rate in water cycle by the

control valves of the water flow through main and

bypass pipes before the test tube or adjust by

controlling the input water flow rate adjusting knob

in the water heater at (5 lmin)

5 Adjust the required outlet temperature from the water

heater at inlet of the test section manually by

adjusting the knob of the flame or the knob of water

flow rate input to the heater

6 Watch the reading of water inlet and outlet

temperatures till the steady state conditions reached

(40-60) minutes Then take the following readings

7 Water temperatures for inlet and outlet of the test

tube b) Air temperatures for entering and leaving the

Engineering and Technology 2015 2(2) 23-34 27

test duct before and after the test tube c) The surface

temperature to the test tube by thermal imager d)

The atmospheric temperature e) The inlet and outlet

pressure (pressure drop in the test tube)

8 Repeat the experimental procedure for every case by

changing air velocity inlet water temperature and by

replacing the test sections (smooth and integral low

finned tube eight passes)

3 Theoretical Analysis

The first law of thermodynamics requires that the rate of

heat transfer from the hot fluid be equal to the rate of heat

transfer to the cold one or

= minus13 and

= 13 minus The rate of heat transfer in a heat exchanger can also be

expressed in the following form [2 19]

= ∆

For counter flow

∆ = ∆∆∆∆

= ∆∆∆∆n

∆ = 13 minus

∆ = minus 13 The actual logarithmic mean temperature difference of a

cross flow multi passes heat exchanger is obtained by [20

21]

∆ = ∆

then for cross flow

= ∆

The correction factor (Fcle 1) depends on the geometry of

the heat exchanger the inlet and outlet temperatures of the

hot and cold fluid streams number of tube rows and number

of passes The correction factor can be expressed as function

of the dimensionless ratios (R and S) given by [20 21]

= 13 minus minus 13

amp = ())) and

= + + 1ln 0102 minus 1 ln 3 0415+156 04155+1567

31 Water Side

The recommended correlation presented by [22] to predict

the heat transfer coefficient in a turbulent flow in tube is

89 = 0023gtABC

where Prandtl number index (n) is equal to (03) for cooling

process and this equation is valid for a turbulent flow with

(06 ltPrlt100) then the heat transfer coefficient equal to

ℎ13 = 0023gtEABC FEG13

where the Reynolds number based on the tube inside

diameter is

gtE =HE9EG13IE

or

gtE =GJKμE

where

K = EJ

13 = N4G13

and

AB = IEEPE

then

13 = 13Q∆

32 Air Side

The air side heat transfer coefficient general equation is

given in the form

For a smooth tube [19 22]

ℎ = 1R( minus

S([U(U) ] WX minus S()S)

And for an integral low finned tube [18]

ℎ = 1R( minus

S(Y[UZU) ] WX minus S(Y)S)

can be calculated using

1313Q = Q

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

Engineering and Technology 2015 2(2) 23-34 27

test duct before and after the test tube c) The surface

temperature to the test tube by thermal imager d)

The atmospheric temperature e) The inlet and outlet

pressure (pressure drop in the test tube)

8 Repeat the experimental procedure for every case by

changing air velocity inlet water temperature and by

replacing the test sections (smooth and integral low

finned tube eight passes)

3 Theoretical Analysis

The first law of thermodynamics requires that the rate of

heat transfer from the hot fluid be equal to the rate of heat

transfer to the cold one or

= minus13 and

= 13 minus The rate of heat transfer in a heat exchanger can also be

expressed in the following form [2 19]

= ∆

For counter flow

∆ = ∆∆∆∆

= ∆∆∆∆n

∆ = 13 minus

∆ = minus 13 The actual logarithmic mean temperature difference of a

cross flow multi passes heat exchanger is obtained by [20

21]

∆ = ∆

then for cross flow

= ∆

The correction factor (Fcle 1) depends on the geometry of

the heat exchanger the inlet and outlet temperatures of the

hot and cold fluid streams number of tube rows and number

of passes The correction factor can be expressed as function

of the dimensionless ratios (R and S) given by [20 21]

= 13 minus minus 13

amp = ())) and

= + + 1ln 0102 minus 1 ln 3 0415+156 04155+1567

31 Water Side

The recommended correlation presented by [22] to predict

the heat transfer coefficient in a turbulent flow in tube is

89 = 0023gtABC

where Prandtl number index (n) is equal to (03) for cooling

process and this equation is valid for a turbulent flow with

(06 ltPrlt100) then the heat transfer coefficient equal to

ℎ13 = 0023gtEABC FEG13

where the Reynolds number based on the tube inside

diameter is

gtE =HE9EG13IE

or

gtE =GJKμE

where

K = EJ

13 = N4G13

and

AB = IEEPE

then

13 = 13Q∆

32 Air Side

The air side heat transfer coefficient general equation is

given in the form

For a smooth tube [19 22]

ℎ = 1R( minus

S([U(U) ] WX minus S()S)

And for an integral low finned tube [18]

ℎ = 1R( minus

S(Y[UZU) ] WX minus S(Y)S)

can be calculated using

1313Q = Q

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

28 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

gt[ =H[9[GI[

G = 4SA 4 ]2 ]

then89[ for a smooth tube

89[ D ^ GF[

And for an integral low finned tube

89[ D ^ GF[

33 Effectiveness

The effectiveness is the ratio of the actual of heat transfer

to the maximum possible amount of heat transfer during the

operation of heat exchanger or [23]

` [a[b

at

[a 13 13

and

[b 13C13 13 where

13C

is the minimum heat capacity of hot or cold fluid

For cross ndash flow heat exchanger with one of the fluids

unmixed and other mixed the relation between effectiveness

and number of transfer unit (NTU) is given by[22]

For Cmax mixed Cmin unmixed

ε 1d1 gteT1 gtfRVg For Cmax unmixed Cmin mixed

` 1 gte h 1T1 gte8 Vi where

13C[b

is the heat capacity ratio

The (NTU) is a function of the overall heat transfer

coefficient in the form

8 Q13C

34 Enhancement Ratio Factor

The enhancement ratio factor (EF) is given by [24]

k Dl13CCmSDQa

35 Water side Pressure Drop

The pressure drop caused by fluid friction in the tubes is

given by [25]

∆Aaa[ ∆AQa[13naaopmQ

∆A13Cl13aa13CnQ where from Darcy ndash Weisbach equation

∆AQa[13naaopmQ q rst uG13 v wH 9 2 x

For turbulent flow in a smooth pipe the Blasius correlation

valid for Re le 105 is[26]

q 0316gt z

Pressure losses due to the minor fittings is[25]

∆A[13Cl13aa13CnQ sl13aH w9 2 x

where (k) is the losses coefficient

4 Present Correlation

Figure (4) Sample of curve fitting for empirical relation

In this paper it was suggested to develop empirical

correlations for the air side heat transfer coefficient to an

integral low finned tube based on the general correlation for

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

Engineering and Technology 2015 2(2) 23-34 29

air side Nusselt number in cross flow over tube or cylinder

[22]

89[ gt[CAB |

where C and n are constants obtained from the experimental

results as shown in fig( 4 )The empirical relations are given

in table (1) valid for (20838 ltRealt 63605)

5 Results and Discussion

The experimental data and results of the measurements for

the smooth and integral low finned tube at eight passes

indicated that

bull The temperature difference in water side (∆Tw)

increases with increase inlet water temperature

bull The temperature difference in air side (∆Ta) increases

with increase inlet water temperature and the outlet

air temperature increase with increase inlet water

temperature

bull The average surface temperature (Tsave) increases

with increase inlet water temperature and the cooling

value of tube surface increases with increase inlet

water temperature

The results of calculation for the water side pressure drop

(∆Pw) in the test tube which indicate that the water flow rate

has the main effect on the pressure drop ie the pressure

drop increases with increase the water flow rate due to

increase the friction

Figure (5) shows the relation between the heat load and

inlet water temperature at different air velocity for smooth

and integral low finned tube eight passes It is obvious that

the heat load increases with increase inlet water temperature

due to the increase in the temperature difference between the

air temperature and surface tube temperature The heat load

increases with increase the air velocity due to the

improvement of the overall heat transfer coefficient of the

test tube by increasing the air side heat transfer coefficient

The figure shows that the heat load of the integral low finned

tube is higher than that of the smooth tube The heat load of

the finned tube increased by (18 to 213) times that of

smooth tube due to increase the heat transfer surface area

(a) (b)

Figure (5) The variation of the heat load with inlet water temperature at (a) smooth tube eight passes and (b) integral low finned tube eight passes

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

30 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (6) The variation of the air side heat transfer coefficient with air velocity for smooth and integral low finned tube eight passes at water flow rate (5

lmin)

Figure(6) illustrates the variation of the air side heat

transfer coefficient (ho) with air velocity for smooth and

integral low finned tube The outside heat transfer coefficient

increased with increase the air velocity which showed that

increasing of air velocity will improve the outside heat

transfer coefficient due to increase the turbulence The air

side heat transfer coefficient of the integral low finned tube is

higher than that of the smooth tube The enhancement ratio

factor (EF) in the air side heat transfer coefficient when using

the integral low finned tube (EF the ratio between the air

side heat transfer coefficient when using the integral low

finned tube to the air side heat transfer coefficient when

using the smooth tube ( ho finned ho smooth)) was ( 186 to 238)

for eight passes This was a result of the increase in the heat

transfer surface area and the effect of the turbulence

introduced by increasing the air velocity between fins

Figure (7) illustrates the variation of the air side

temperature difference (∆Ta) with air velocity at various inlet

water temperatures The air side temperature difference tends

to decrease with an increase in air velocity In addition at the

same air velocity the air side temperature difference at the

higher inlet water temperature is higher than at the lower one

across the range of air velocity ie the air side temperature

difference increases with increase inlet water temperature due

to increase the heat load

Figure (8) shows the variation of the air side Nusselt

number with air side Reynolds number for smooth and

integral low finned tube The air side Nusselt number

increased with increase the air side Reynolds number This is

because the air side Nusselt number is a function of the air

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

Engineering and Technology 2015 2(2) 23-34 31

side heat transfer coefficient and the air side Reynolds

number is a function of air velocity therefore the behavior of

this figure is similar to the behavior shown in the figure for

the relation between the air side heat transfer coefficient with

air velocity (figure 6)Hence this figure indicates that

increasing of air side Reynolds number will improve the

outside Nusselt number due to increase the turbulence The

air side Nusselt number of the integral low finned tube is

higher than that of the smooth tube and the enhancement

ratio factor was approximately equal to the enhancement

ratio in the air side heat transfer coefficient This was a result

of the increase in the heat transfer surface area and the effect

of the turbulence introduced by increasing the air velocity

between fins

Figure (9) depicts the variation of the effectiveness for the

test tube with the number of transfer units (NTU) at (Cr) in

the range of (041 to 084) The figure shows that increasing

the (NTU) for a specified (Cr) caused an increase in the

effectiveness values of the test tube This is due to the

dependence of the (NTU) and the effectiveness on the overall

heat transfer coefficient therefore the increasing of the

(NTU) means that the overall heat transfer coefficient

increased at the given surface area and this led to increase

the effectiveness

Table (1) Empirical and practical relations for integral low finned tube eight passes

Water flow rate = 5 lmin

Twin C n Empirical Relations R2

50 88323 03537 Nua = 88323 (Rea)03537 Pr13 0991349

60 38435 03996 Nua = 38435 (Rea)03996 Pr13 0999919

70 44566 03685 Nua = 44566 (Rea)03685 Pr13 0999998

80 702795 03148 Nua = 702795 (Rea)03148 Pr13 0999057

(a) (b)

Figure (7) The variation of the air side temperature difference with air velocity at (a) smooth tube eight passes and (b) integral low finned tube eight passes

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

32 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

Figure (8) The variation of the air side Nusselt number with air side Reynolds number for smooth and integral low finned tube eight passes at water flow rate

(5 lmin)

(a) (b)

Figure (9) The variation of effectiveness with (NTU) at (a) smooth tube eight passes and (b) integral low finned tube eight passes

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

Engineering and Technology 2015 2(2) 23-34 33

6 Conclusions

The following points can be concluded from the present

experimental work

1 The heat load from the test tube is directly

proportional to both the inlet water temperature and

the air velocity

2 The heat load of the integral low finned tube is higher

than that of the smooth tube The heat load of finned

tube was enhanced by (18 to 213) times the heat

load of smooth tube

3 The increasing of air velocity will improve the

outside heat transfer coefficient

4 The air side heat transfer coefficient of the integral

low finned tube is higher than that of the smooth tube

The enhancement ratio factor (EF) in the air side heat

transfer coefficient when using integral low finned

tube was (186 to 238) for eight passes And this

enhancement ratio from the use of the integral low

finned tube is very useful to increase the heat load

and the effectiveness

5 The air side temperature difference and outlet air

temperature are inversely proportional to the air

velocity and directly proportional to the inlet water

temperature

6 The air side Nusselt number is directly proportional

to air side Reynolds number The air side Nusselt

number of the integral low finned tube is higher than

that of the smooth tube And the enhancement ratio

was approximately equal to the enhancement ratio in

the air side heat transfer coefficient

The pressure drop in the test tube is directly proportional

to water flow rate

Nomenclature

A Area [m2]

Ad c Cross section area of duct [m2]

Ai c Inner cross section area of tube [m2]

Ai s Inner surface area of tube [m2]

Ao s Outer surface area of tube [m2]

C Heat capacity [ kWoC]

cp Specific heat of fluid [ kJkgoC ]

Cr Heat capacity ratio

d Diameter [m]

dh Hydraulic diameter [m]

do f Outer diameter of finned tube [m]

dr Root diameter [m]

f Friction factor

Fc Logarithmic mean temperature correction factor

G Mass velocity [kgm2sec]

h heat transfer coefficient [Wm2oC]

H Height of the duct [m]

K Thermal conductivity [WmoC]

L Length of tube [m]

Mass flow rate [kgsec]

nfit Number of fitting

np Number of tube passes

Nu Nusselt number

Pr Prandtl number

P∆ Pressure drop [Pa]

Q Heat load [kW]

R2

Correlation Coefficient

Re Reynolds number

T Temperature [oC]

T c i Inlet temperature of cold fluid [oC]

T c o Outlet temperature of cold fluid [oC]

T h i Inlet temperature of hot fluid [oC]

T h o Outlet temperature of hot fluid [oC]

∆T Temperature difference [oC]

∆ Logarithmic mean temperature difference [oC]

u Fluid velocity [msec]

U Overall heat transfer coefficient [Wm2oC]

W Width of the duct [m]

Heat exchanger effectiveness

micro Fluid viscosity [kgmsec]

ρ Fluid density [kgm3]

References

[1] S P Sukhatme B S Jagadish and P Prabhakaran ldquoFilm Condensation of R-11Vapor on Single Horizontal Enhanced Condenser Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol112 pp229-234 1990

[2] WessamFalih Hasan ldquoTheoretical and Experimental Study to Finned Tubes Cross Flow Heat Exchange ldquo Master thesis Mech Eng Dept University of Technology 2008

[3] Virgil J Lunardini and Abdul Aziz ldquoEffect of Condensation on Performance and Design of Extended Surfaces ldquo CRREL Report 95-20 Cold Regions Research and Engineering Laboratory 1995

[4] R K Al-Dadah and T G Karayiannis ldquoPassive Enhancement of Condensation Heat Transferldquo Applied Thermal Engineering 18 pp895-909 1998

[5] Wolverine Tube Inc ldquoWolverine Engineering Data Book II ldquo 2001

[6] Wolverine Tube Inc ldquoWolverine Engineering Data Book III ldquo was updated in 2007

[7] DG Rich ldquoThe Effect of Fin Spacing on the Heat Transfer and Friction Performance of Multi-Row Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 79 No2 pp135-145 1973

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995

34 Laith Jaafer Habeeb et al Heat Transfer Analysis of Integral-Fin Tubes

[8] D G Rich ldquoThe Effect of the Number of Tube Rows on Heat Transfer Performance of Smooth Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions Vol 81 pp 307-317 1975

[9] Brown R ldquo A Procedure for Preliminary Estimates of Air Cooled Heat Exchangersrdquo in Chemical Engineering McGraw-Hill Publication Book Co Newyork pp412-417 1997

[10] CC Wang KY Chi YJ Chang and YP Chang ldquoA Comparison Study of Compact Plate Fin-and-Tube Heat Exchangersrdquo ASHRAE Transactions TO-98-3-3 1998

[11] Fethi Halici and Imdat Taymaz ldquoExperimental Study of the Airside Performance of Tube Row Spacing in Finned Tube Heat Exchangersrdquo Heat Mass Transfer 42 pp817ndash822 2006

[12] Han-Taw Chen and Wei-Lun Hsu ldquoEstimation of Heat-Transfer Characteristics on a Vertical Annular Circular Fin of Finned-Tube Heat Exchangers in Forced Convectionrdquo International Journal of Heat and Mass Transfer 51 pp1920ndash1932 2008

[13] Jong Min Choi Yonghan Kim Mooyeon Lee and Yongchan Kim ldquoAir Side Heat Transfer Coefficients of Discrete Plate Finned-Tube Heat Exchangers with Large Fin Pitchrdquo Applied Thermal Engineering 30 pp174ndash180 2010

[14] H Honda S Nozu and Y Takeda ldquoA Theoretical Model of Film Condensation in a Bundle of Horizontal Low Finned Tubes ldquo Transactions of the ASME Journal of Heat Transfer Vol111 pp525-532 1989

[15] W Y Cheng C C Wang Y Z Robert Hu and L W Huang ldquoFilm Condensation of HCFC-22 on Horizontal Enhanced Tubesldquo Int Comm Heat Mass Transfer Vol 23 No1 pp79-90 1996

[16] Ravi Kumar H K Varma BikashMohanty and K N Agrawal ldquoPrediction of Heat Transfer Coefficient during Condensation of Water and R-134a on Single Horizontal Integral-Fin Tubes ldquo International Journal of Refrigeration 25 pp111-126 2002

[17] Ali Hussain Tarrad ldquoA Numerical Model for Thermal-Hydraulic Design of a Shelland Single Pass Low Finned Tube Bundle Heat Exchangerldquo Eng amp Technology Vol 25 No 4 pp619-645 2007

[18] Joseacute Fernaacutendez-Seara Francisco J Uhıacutea and RubeacutenDiz ldquoExperimental Analysis of Ammonia Condensation on Smooth and Integral-Fin Titanium Tubes ldquo International Journal of Refrigeration 32 pp1140-1148 2009

[19] Frank B Incropera and David B Doot ldquoPrinciples of Heat Transfer ldquo McGraw-Hill Co 1986

[20] R K Sinnott ldquoChemical Engineering Design ldquo Volume 6 Fourth edition Elsevier Butterworth-Heinemann 2005

[21] Ali Hussain Tarrad Fouad Alwan Saleh and Ali Ahmed Abulrasool ldquo A Simplified Numerical Model for a Flat Continuous Triangle Fins Air Cooled Heat Exchanger Using aStep by Step Technique ldquo Journal of Engineering and Development Vol13 No 3 pp38-60 2009

[22] J P Holman ldquoHeat Transfer ldquo Ninth editionMcGraw-Hill Co 2002

[23] Ali Hussain Tarrad Marsquoathe AbulWahed and Dhamiarsquoa Saad Khudor ldquoA Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation ldquo Journal of Engineering and Development Vol12 No 3 pp88-119 2008

[24] Satesh Namasivayam and Adrian Briggs ldquoEffect of Vapour Velocity on Condensation of Atmospheric Pressure Steam on Integral-Fin Tubes ldquo Applied Thermal Engineering 24 pp1353ndash1364 2004

[25] American Society of Heating Refrigeration and Air Conditioning Engineers ldquoASHRAE Fundamentals Handbook ldquo Chapter 22 pp221-2221 2009

[26] Victor L Streeter E Benjamin Wylie and Keith W Bedford ldquoFluid Mechanicsrdquo Ninth edition McGraw-Hill Co 1995