heat transfer lab manual 2015-16

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Laboratory Manual

For

HEAT TRANSFER

ME F311

BY

DEPARTMENT OF MECHANICAL ENGINEERING

EDUCATIONAL DEVELOPMENT DIVISIONBirla Institute of Technology & Science, Pilani – K.K. Birla Goa Campus

GOA- 403 726

2015-2016



LIST OF EXPERIMENTS

S. No. Title of the Experiment Page No.

No. of

Tear off

Sheets

Thermal Science Lab (A110)

1 Heat Transfer through Lagged Pipe 1-4 1

2 Stefan Boltzmann Apparatus 5-7 1

3 Emissivity Measurement Apparatus 8-10 1

4 Heat Transfer in Natural Convection 11-13 1

5 Drop wise and Film Condensation 14-20 2

6 Heat Transfer from a Pin Fin 21-26 1

7 Thermal Conductivity of Liquids 27-30 1

8 Thermal Conductivity of Insulating Powder 31-33 1

9 Heat Transfer in Forced Convection 34-37 1

10 Heat Pump Trainer 38-41 1

11 To Determine the Coefficient of Performance (COP) of a Vapor

Compressor Trainer 42-45 1

12 Vapor Absorption Refrigeration Trainer 46-51 1

13 Air Conditioning Trainer 52-61 5

14 Parallel and Counter Flow Heat Exchanger 62-65 2

15 Shell and Tube Heat Exchanger 66-69 2



ii

DESCRIPTION OF LABORATORY

Transport Phenomena laboratory is a hands-on investigation of momentum and

heat transfer. Friction factor; conductivity, convective and diffusion coefficient

measurements; velocity and temperature determination, engineering instrumentation and

experimental analysis of data are some of the tasks in this laboratory.

The experiments focus on demonstration or verifying transport phenomena

principles. The scope is limited to one- dimensional systems and experiments in

momentum transfer and heat transfer are included.

Objectives of the Laboratory component

To supplement theory by enhancing the understanding of basic concepts of

momentum and heat transfer operations.

To gain insight and appreciation for the inherent link between theory and

practical.

To reinforce concepts and principles of Transport Phenomena established in

lecture course through hands- on experience and experience with order of

magnitude and exploration of range of applicability of transport models and

predicted behavior.

To illustrate to the students by actual measurements based on experimental work,

some of the basic laws and principles of momentum and heat transfer.

To provide intensive experience in conducting experiments in laboratory,

analyzing and interpreting data.

To provide experience in engineering measurement and experimentation.

In addition, students get experience in technical communication in the form of

written laboratory reports



iii

The brief focus of the experiments to be conducted in two laboratories is

given below

Fluid Mechanics Laboratory

The momentum transfer experiments in this laboratory are based on portion

studied in the Transport Phenomena- I course. The laboratory has two hydraulic benches,

experimental set up for losses in pipes, Impact of Jet, free and forced vortex. All these set

up can be kept on hydraulic bench to perform experiment. Addition to these, this lab has

got Darcy’s Law apparatus and Drag coefficient apparatus.

These experiments are aimed to expose the complexities involved in

measurements of fluid variables like pressure drop, velocity, flow rate etc. and the

devices used for these measurements. The experiments are based on application of

Bernoulli Equation, Energy Equation and Boundary Layer Phenomena.

Thermal Science Laboratory

Thermal Transport Phenomena play a key role in the development of almost every

emerging technology. For instance, one of the main factors for the development of faster

microchips that exit today is effective removal of the heat generated within the chips. To

gain understanding of heat transfer in different areas, it is important to have a feel for

heat transfer in several basic situations.

The laboratory has got experiment through which one can learn how to measure

thermal conductivity, heat transfer coefficient and emmisivity. It has two heat

exchangers, drop wise and film wise condensation apparatus. These experiments aimed to

understand heat transfer problem and correlations based on experiments, which is the

only source when approaching a heat transfer problem. Addition to these, this lab has got

Heat pump, Refrigeration (vapor absorption and compression) test rig and Air conditioner

test rig to find their coefficient of performances.



Heat Transfer Lab Manual

1

Experiment 1

HEAT TRANSFER THROUGH LAGGED PIPE

Objective:

To determine heat flow rate through the lagged pipe for known value of thermal

conductivity of lagging material and get the combined thermal conductivity of lagging

material. Plot the temperature distribution across the lagging material.

Theory:

Consider a long cylinder of inside radius r i, and length L. We expose this cylinder to

a temperature differential T i -T O and see what the heat flow will be. For a cylinder with

length very large compared to diameter, it may be assumed that the heat flow in a radial

direction, so that the only space coordinate needed to specify the system is ‘r ’. In cylindrical

system the Fourier’s law is written

2

2

r

r

dT Q kA

dr A rL

dT Q krL

dr

with the boundary conditions

T = T i at r = r i

T = T o at r = r o

The solution to equation is

2

lni o

o i

kL T T Qr r

and the isothermal resistance in this case is

kL

r r R io

th 2

ln

The thermal-resistance concept may be used for multiple-layer cylindrical walls just

as it was used for plane walls. For the two layer system the solution is




2

1 3

2 1 3 2

2

ln ln B

kL T T Q

r r k r r k

Description:

The apparatus consist of three concentric pipe mounted on suitable stands. The

inside pipe consists of the heater. Between first two cylinders the insulating material with

which lagging is to be done is asbestos and in second and third pipe is wooden dust.

The Thermocouples are attached to the surface of cylinders appropriately to measure

the temperatures. The input to the heater is varied through a dimmerstat and measured on a

voltmeter, ammeter. The experiments can be conducted at various values of input and

calculations can be made accordingly.

Experimental Procedure:

1. Start the supply of heater & by varying dimmerstat adjusts the input for desired values

by using voltmeter and ammeter.

2. Take readings of all the 6 thermocouples at the interval of 10 minutes until the said

steady state is reached.

3. Note down steady state readings in observation table.

(Assumptions: The pipe is so long as compared with diameter that heat flows in radial

direction only in middle half section.)

Formulae:

1. Heat input, Q V I

Experimental heat flow rate through the composite cylinder (for two insulating layers)

1 0 2

2 ( )[ln( / ) / ] [ln( / ) / ]

i o

Exp

m i m

L T T Qr r k r r k

2. From known value of heat flow rate, value of combined thermal conductivity, k eff of

lagging material can be calculated:

0

2 ( )

ln( / )

eff i o

Exp

i

Lk T T Q

r r




3

0ln( / )

2 ( )

Exp i

eff

i o

Q r r k

L T T

3. To plot the temperature distribution use formula:-

1

0

ln( / )

ln( / )

i

o i i

T T r r

T T r r

Thus the plot of T Vs r (thickness) can be made for different values of r.

Mean Readings:

Inside, 1 2

2i

T T T

Middle, 3 4

2m

T T T

Outside, 5 6

02

T T T

Nomenclature:

k = thermal conductivity of material, W/ mK

A = heat transfer area, m2

q = heat transfer rate, W

r i = inside radius of the pipe, m

r o = outside radius of the pipe, m

T i = inside temperature of the pipe,0C

T o = outside temperature of the pipe,0C

L = length of the pipe, m

Exercises:

1. Find the heat flow rate through the lagged pipe.

2. Calculate the combined thermal conductivity of lagging material.

3. Plot temperature profile.




4

Precautions & Maintenance Instructions:

1. Use the stabilize A.C. Single Phase supply only.

2. Never switch on mains power supply before ensuring that all the ON/OFF switchesgiven on the panel are at OFF position.

3. Voltage to heater starts and increases slowly.

4. Keep all the assembly undisturbed.

5. Never run the apparatus if power supply is less than 180 volts and above than 240 volts.

6. Operate selector switch of temperature indicator gently.

7. Always keep the apparatus free from dust.

There is a possibility of getting abrupt result if the supply voltage is fluctuating or if the

satisfactory steady state condition is not reached.




5

Experiment 2

STEFAN BOLTZMANN APPARATUS

Objective:

To study radiation heat transfer by a black body hence finds the Stefan Boltzmann

constant.

Theory:

The most commonly used law of thermal radiation is the Stefan Boltzmann law

which states that emissive power of a black body is proportional to the fourth power of

absolute temperature of the surface and is given by

The constant of proportionally is called the Stefan Boltzmann constant and has the

value of 5.67 x 10-8

W/m2

K 4. The Stefan Boltzmann law can be derived by integrating the

Planck’s law over the entire spectrum of wavelength from 0 to . The objective of this

experimental set up is to measure the value of this constant fairly closely, by an easyarrangement.

Description:

The apparatus is centered on a flanged copper hemisphere fixed on a flat non-

conducting base plate. The outer surface of hemisphere is enclosed in a metal water jacket

used to heat it to some suitable constant temperature.

One Temperature Sensor is attached to the inner wall of hemisphere to measure its

temperature and to be read by a temperature indicator. The disc, which is mounted in an

insulating bakelite sleeves is fitted in a hole drilled in the centre of the base plate. A

Temperature Sensor is used to measure the temperature of disc i.e. TD. The Temperature

Sensor is mounted on the disc to study the rise of its temperature.

4

b E T




6

When the disc is inserted at the temperature TD its temperature increases with time‘t’

since it receives heat by radiation from hemisphere. This time‘t’ is used to calculate the

Stefan Boltzmann constant.

The inner surface of hemisphere and base plate forming the enclosure are blacked by

using lamp black to make their absorptivity to be approximately unity. The copper surface of

the disc is also blackened.


1. Heat the water in the tank by the immersion heater up to a temperature of about 70 -

90C.

2. The disc should be removed before pouring the hot water in the jacket.

3. The hot water is to be poured in the water jacket.

4. The hemispherical enclosure and the base plate will come to some uniform

temperature in a short time after filling the hot water in the jacket. The thermal inertia

of hot water is quite adequate to prevent significant cooling in the time required to

conduct the experiment.

5. The enclosure will soon come to thermal equilibrium conditions.

6. The disc is now inserted in the base plate at a time (t = 0) when its temperature is TD.7. Start noting the temperature change for every five second for a minute.

Formulae:

1. = 0

4 4

( / )

( )

t

D h D

ms dT dt

A T T

2. AD =2

4

Dd

Nomenclature:

AD = Area of disc D, m2

Th = Temperature of hemisphere enclosure,0C

TD = Temperature of disc at time t = 0,0C

m = mass of disc, kg




7

s = specific heat of the disc material, kJ/ kg0C

Exercises:

1. Plot a graph temperature of disc Vs time.

2. Determine the value of Stefan Boltzmann constant.

3. Write your comments on the above results.


1. Always use clean water and heater should be completely dipped in the water before

switch ON the heater.

2. Always take the reading for the first min. of the disc while fixing.


4. Never switch on mains power supply before ensuring that all the ON/OFF switches

given on the panel are at OFF position.

5. Voltage to heater should be constant.


7. Never run the apparatus if power supply is less than 180 V and above than 240 V.



10. Don’t switch ON the heater before filling the water into the bath.

There is a possibility of getting abrupt result if the supply voltage is fluctuating or if

the satisfactory steady state condition is not reached.




8

Experiment 3

EMISSIVITY MEASUREMENT APPARATUS

Objective:

To find out the emissivity of a test plate.

Theory:

An idealized black surface is one, which absorbs all the incident radiation with

reflectivity and transmissivity equal to zero. The radiant energy per unit time per unit area

from the surface of the body is called as the emissive power and is usually denoted by E.

The emissivity of the surface is the ratio of the emissive power of the surface to the

emissive power of a black surface at the same temperature. If is noted by ε.

b

E

E

For black body absorptivity = 1 and by the knowledge of Kirchoff's Law of

emissivity of the black body becomes unity. Emissivity being a property of the surface

depends on the nature of the surface and temperature. The present experimental set up is

designed and fabricated to measure the property of emissivity of the test plate surface at

various temperatures.

Description:

The experimental set up consists of two circular copper plates identical in size and is

provided with heating coils sand witches. The plates are mounted on bracket and are kept in

an enclosure so as to provide undisturbed natural convection surroundings. The heating

input to the heater is varied by separate dimmerstat and is measured by using an ammeter

and a voltmeter with the help of double pole double throw switches. The temperature of the plates is measured by Pt-100 sensor. Another Pt-100 sensor is kept in the enclosure to read

the ambient temperature of enclosure.

Plate 1 is blackened by a thick layer of lampblack to form the idealized black surface

where as the plate 2 is the test plate whose emissivity is to be determined. The heater inputs

to the two plates are dissipated from the plates by conduction, convection and radiation. The




9

experimental set up is designed in such a way that under steady state conditions the heat

dissipation by conduction and convection is same for both the cases. When the surface

temperatures are same the difference in the heater input readings is because of the difference

in radiation characteristics due to their different emissivities.


1. Gradually increase the input to the heater to black plate and adjust it to some value and

adjust heater input to test plate slightly less than the black plate.

2. Take readings of all the 3 thermocouples at the interval of 10 minutes until the said

steady state is reached.

3. After attaining the steady state conditions record the Voltmeter and Ammeter reading for

both the plates.

Specification:

1. Test plate dia = 160 mm

2. Black plate = 160 mm

3. Dimmerstat for both plates = 0-2 A, 0-220V.

4. Voltmeter = 0-250V, Ammeter 0-2.5 A5. RTD Temperature sensor = 3 Nos

6. Heater for test plate and black plate Nichrome strip wound on mica sheet and sand-

witched between two mica sheets of 440 Watt.

Formulae:

1. 4 4

b b sq A T T

2. 4 4

t t t sq A T T

3. εt = Emissivity of the test plate to be determined.

4 4

4 4

0.86

0.86

b sb

t t t s

A T T W

W A T T




10

Nomenclature:

qb = heat input to disc coated with lamp black (W)

= W b x 0.86

W b = wattage supplied to black plate

qt = heat input to test plate (W)

= W t x 0.86

W t = wattage supplied to test plate

= Stefan Boltzmann Constant = 5.67 10-8

W/ m² K 4

A = area of disc (m2)

T b = surface temperature of black plate disc, K

T t = surface temperature of test plate disc, K

T s = ambient temperature of enclosure, K

εt = emissivity of the test plate to be determined.

εb = emissivity of black body.

Exercises:

1. Find the emissivity of the test plate


1. Use the stabilize A.C. Single phase supply only.




4. Keep all the assembly undisturbed.5. Never run the apparatus if power supply is less than 180 volts and above than 240

volts.






11

Experiment 4

HEAT TRANSFER IN NATURAL CONVECTION

Objective:

To find out the heat transfer co-efficient of vertical cylinder in natural convection.

Theory:

Natural convection phenomenon is due to the temp. Difference between the surface

and the fluid and is not created by any external agency. The Setup is designed and

fabricated to study the natural convection phenomenon from a vertical cylinder in terms of

average heat transfer coefficient.

The heat transfer coefficient is given by.

( )

a

s a

Qh

A T T

W/ m

2K

Description:

The apparatus consists of a brass tube fitted in a rectangular duct in a vertical

fashion. The duct is open at the top and bottom and forms an enclosure and serves the

purpose of undisturbed surrounding. One side of it is made up of glass/acrylic for

visualization. A heating element is kept in the vertical tube, which heats the tube surface.

The heat is lost from the tube to the surrounding air by natural convection. Digital

temperature indicator measures the temperature at the different points with the help of seven

temperature sensors. The heat input to the heater is measured by digital ammeter and digital

voltmeter and can be varied by a dimmerstat.




12


1. Clean the apparatus and make it free from dust, first.

2. Ensure that all On/Off switches given on the panel are at OFF position.

3. Ensure that variac knob is at ZERO position, given on the panel.

4. Now switch on the main power supply (220 V AC, 50 Hz).

5. Switch on the panel with the help of mains On/Off switch given on the panel.

6. Fix the power input to the heater with the help of variac, voltmeter and ammeter

provided.

7. After 30 minutes record the temperature of test section at various points in each 5

minutes interval.8. If temperatures readings are same for three times, assume that steady state is

achieved.

9. Record the final temperatures.

Specification:

Dia of the tube = 35 mm

Length of the tube = 500 mm

Size of duct = 25 25 90 cm

Temperature Sensors = RTD PT-100 type

No. of RTD Temperature Sensors = 8 Nos.

Digital Voltmeter = 0 to 250 V

Digital Ammeter = 0 to 2.5 Amps

Dimmerstat = 2 Amps/220 V

Temperature Indicator = Digital temperature indicator 0 to

200oC with multi channel switch.




13

Formulae:

1. The heat transfer coefficient,

h =( )

a

s a

Q

A T T W/m

2.K

Where

Qa = heat transfer rate = V I (W)

A = Area of the heat transferring surface = d L (m²)

1 2 3 4 5 6 7

7 s

T T T T T T T T

T a = ambient temperature in duct C = T 8

Exercises:

1. Find out the heat transfer co-efficient of vertical cylinder in natural convection


1. Use the stabilize A.C. single phase supply only.2. Never switch on mains power supply before ensuring that all the ON/OFF switches




5. Never run the apparatus if power supply is less than 180 V and above than 240 V.








15

static beads along its downward in its trail. The ‘bare’ surface offers very little resistance to

the transfer of heat and very high heat fluxes are therefore possible.

Unfortunately, due to the nature of the material used in the construction of

condensing heat exchangers, Filmwise condensation is normal. (Although many bare metal

surfaces are ‘non - wettable’ this is not true of the oxide film which quickly covers the bare

material)

Description:

The equipment consists of a metallic container in which steam generation takes

place. The lower portion houses suitable electric heater for steam generation. A special

arrangement is provided for the container for filling the water. The glass cylinder housestwo water cooled copper condensers, one of which is chromium plated to promote Dropwise

condensation and the other is in its natural state to give Filmwise condensation. A

connection for pressure gauge is provided. Separate connections of two condensers for

passing water are provided. One Rota meter with appropriate piping can be used for

measuring water flow rate in one of the condensers under test.

A digital temperature indicator provided has multipoint connections, which measures

temperatures of steam, two condensers, water inlet & outlet temperature of condenser water

flows.


1. Fill water in steam generator by opening the valve.

2. Start water flow through one of the condensers, which is to be tested and note down

water flow rate in Rota meter. Ensure that during measurement, water is flowing only

through the condenser under test and second valve is closed.

3. Connect supply socket to mains and switch ON the heater switch.

4. Slowly steam generation will start in the steam generator of the unit and the steam rises

to test section, gets condensed on the tubes and falls down in the cylinder.

5. Depending upon type of condenser under test Dropwise or Filmwise can be visualized.




16

6. If the water flow rate is low then steam pressure in the chamber will rise and pressure

gauge will read the pressure. If the water flow rate is matched then condensation will

occur at more or less atmospheric pressure or up to 1 kg pressure.

7. Observations like temperatures, water flow rates, pressure are noted down in the

observations table at the end of each set.

Specification:

Condensers = One gold plated for Dropwise condensation & one

natural finish for Filmwise condensation otherwise identical

in construction.

Dimensions = 20 mm outer dia. 160 mm length, Fabricated from copper with

reverse flow in concentric tubes. Fitted with temperature

sensor for surface temperature measurement.

Main Unit = M.S. Fabricated construction comprising test section & steam

generation section. Test section provided with glass cylinder

for visualization of the process.

Heating Elements = Suitable water heater.

Instrumentation = 1) Temperature Indicator: Digital 0-199.9

o

C & least count0.1

oC with multi-channel switch.

2) Temperature Sensors: RTD PT-100 Type.

3) Rota meter: for measuring water flow rate.

4) Pressure Gauge: Dial type 0 - 2 Kg/cm2

Formulae:

1. Heat losses from steam s s

Q M

2. Heat taken by cold water w w P

Q M C T

3. Average hear transfer 2

QwQsQ




17

4. Inside heat transfer coefficient i

i

Qh

T

5. Outside heat transfer coefficient o

o

QhT

6. Experimental overall heat transfer coefficient 1 1 1

i

EX i o o

D

U h D h

7. Reynolds Number 1 1

4Re w

d

i

m

D

8. Prandtl Number P

r

C P

K

9. Nusselt Number Nu1 = 0.023 (R ed)0.8

(Pr )0.4

10. Inside heat transfer coefficient K m / W L

K Nuh

21i

11. Out side heat transfer coefficient

25.0

W S

3

2

2

2o

L )T T (

gk 943.0h

12. Theoretical overall heat transfer coefficient 1 1 1i

TH i o o

DU h D h

Nomenclature:

Di = Inner Dia of condenser, m

hi = Inside Heat Transfer Coefficient, W/m2K

T S = Temperature of steam, C.

T W = Temperature of condenser wall, C Ms = Rate of steam condensation, Kg/s

Mw = Cold water flow rate, Kg/s

Cp = Specific heat of water, kJ/kgK

g = Acceleration due to gravity, m/s2

L = Length of condenser, m




18

= Density of water, kg/m3

= Kinematics Viscosity, m2/sec.

k = Thermal conductivity, W/mK

Pr = Prandtl number

T 1 = Surface Temperature of Plated Condenser,oC

T 2 = Surface Temperature of Plain Condenser,oC

T 3 = Temperature of steam in column,oC

T 4 = Water inlet temperature,oC

T 5 = Water outlet temperature,oC

Data:

Outer diameter of heat transfer surface, Do = 20 mm

Inner diameter of heat transfer surface, Di = 17 mm

Length of heat transfer surface, L = 160 mm

Inside heat transfer area, Ai = 0.008549 m2

Outside heat transfer area, Ao = 0.010057 m2

Calculation:

1. Heat transfer coefficient at inner surface

Properties of water at bulk mean temperature of water i.e. (T5 +T6)/2 Where T5 and T6 are

water inlet and outlet temperatures.

Following properties are required. :

CP = Specific heat of water, kJ/kgK

1 = Density of water kg/m3

1 = Kinematics Viscosity m2/sec

μ = Viscosity of water, N.s/m2

k 1 = Thermal conductivity, W /m K

Now calculate

Reynolds’s number 11i

wd

D

m4 Re




20

Observed heat transfer coefficient = expo

h 2

W/m K

Condensation Flux =exp( )

o S h T T

1 1 1

exp exp expi

i o o

D

U h D h

Compare the observed heat transfer coefficient with that calculated.

Exercises:

1. Calculate transfer coefficient at inner surface.

2. Calculate transfer coefficient at outer surface.

3. Find out the overall heat transfer coefficient

4. Same procedure can be repeated for other condenser. Except for some exceptional

cases overall heat transfer coefficient for Dropwise condensation will be higher than

that of Filmwise condensation. Results may vary from theory in some degree due to

unavoidable heat losses.

Precautions and Maintenance instructions:






5. Never run the apparatus if power supply is less than 180 volts and above than 240

volts.


7. Do not start heater supply unless water is filled in the test unit.







21

Experiment 6

HEAT TRANSFER FROM A PIN FIN

Objective:

To study the temperature distribution along the length of a pin fin under free and

forced convection heat transfer and find the fin efficiency.

Theory:

It is obvious that a fin surface stick out from primary heat transfer surface. The

temperature difference with surrounding fluid will steadily diminish as one moves out along

the fin. The design of the fins therefore requires knowledge of the temperature distribution

in the fin. The main object of this experimental set up is to study the temperature

distribution in a simple pin fin.

Fin efficiency =tanhwith fin

without fin

C

f

C

mLq

q mL

The temperature profile within a pin fin is given by:

0

[ ] [cosh ( - ) sinh ( - ) ] [ ] [cosh sinh ]

f

b f

T T m L x H m L x

T T mL H mL

Where T f is the free stream temperature of air; T b is the temperature of fin at its base;

T is the temperature within the fin at any x; L is the length of the fin, D is the fin diameter

and m is the fin parameter.

Fin parameter m = /b

h P k A

The volume coefficient of expansion, 1/ 273.15mf

T , 1/K

Velocity of air = V ’ = Q / cross-sectional area of duct

2

4

24

1

o oC d g H

Q

m

3/s (at temperature = Tf )




23

5. Repeat the same experiment with another H = cm etc.

Specification:

Duct size = 150 mm 100 mm 1000 mm

Diameter of the fin ( D) = 12.7 mm

Length of the fin ( L) = 125 mm

Diameter of the Orifice (d o) = 39 mm

Inner diameter of the delivery pipe (d P ) = 52 mm

Coefficient of discharge (Orifice meter) C o = 0.64

Temperature Indicator = 0-200oC, RTD PT-100 type

RTD PT-100 type Sensors = 6 Nos.

Temperature Sensor no.6 reads ambient temperature in the inside of the duct.

Thermal conductivity of fin material (Brass) = 110 W/ m K

Centrifugal blower with Single-phase motor.

Dimmerstat for heat input control 230 V, 2 Amps.

Heater suitable for mounting at the fin end outside the duct.

Voltmeter 0- 250 V.

Ammeter 0- 2 A.

Free Convection:

Mean temperature of the fin , T m =1 2 3 4 5

( ) /5T T T T T

T mf (Mean film temperature) = ( ) / 2m f

T T

The volume coefficient of expansion , = 1/( 273.15)mf

T

Grashof number, Gr = 3 2( ) / g D T

Using the correlation for free convection:

Nusselt number, Nu = 1/ 40.53( Pr) /

air Gr h D k

Free convective heat transfer coefficient, h = /air

Nu k D

Fin parameter, m = / f

h P k A

Perimeter, P = D




24

Cross-sectional area of fin, A = D2

/ 4

Fin diameter, D = 12.7 10-3

m

Fin length, L = 125 10-3

m

Fin efficiency,tanh

C

f

C

mL

mL

Fin effectiveness =with fin

tanhwithout fin

f

c

c

k P qmL

q hA

Corrective length, LC = ( / 4) L D

Parameter, H = / f

h k m

Theoretical temperature profile within the fin =

0

[ ] [cosh ( - ) sinh ( - ) ] [ ] [cosh sinh ]

f

b f

T T m L x H m L x

T T mL H mL

Taking base temperature, T b = T 1

Forced convection:

Orifice coefficient, Co = 0.64

Volumetric flow rate of air, Q =

2

4

24

1

o oC d g H

H = [ ( / -1)] /100w a

h

Velocity of air, V = Q / a (at ambient fluid temp.)

Velocity of air at mean film temperature,1

( 273.15 ) /( +273.15)mf f

V V T T

Reynolds number, Re = 1 / D V

Using the correlation for force convection:

Nusselt Number, Nu = 0.615 ( Re )0.466

= /air

h D k

Heat transfer coefficient, h = /air

u k D




26

Exercises:

1. Find the fin efficiency

2. Calculate the fin effectiveness

3. Plot the temperature profile within the fin T Vs x





3. Fix the power input to the heater with the help of variac, voltmeter and ammeter

provided.



volts.








27

Experiment 7

THERMAL CONDUCTIVITY OF LIQUIDS

Objective:

To determine the thermal conductivity of a liquid

Theory:

For thermal conductivity of liquids using Fourier’s law, the heat flow through the

liquid from hot fluid to cold fluid is the heat transfer through conductive fluid medium.

Fourier’s equation:

2 1T T

Q kA X

Fourier’s law for the case of liquid

At steady state, the average face temperatures are recorded (T h and T c) along with

the rate of heat transfer (Q). Knowing, the heat transfer area (Ah) and the thickness of the

sample ( X ) across which the heat transfer takes place, the thermal conductivity of the

sample can be calculated using Fourier’s Law of heat conduction.

X

T T kA

X

T kAQ C h

hh

heat transfer area = Ah (area to direction of heat flow)

Description:

The apparatus is based on well-established “Guarded Hot Plate” method. It is a

steady state absolute method suitable for materials, which can be fixed between two parallel

plates and can also be extended to liquids that fill the gap between the plates.

The essential components of the set-up are the hot plate, the cold plate, and heater to

heat the hot plate, cold water supply for the cold plate, RTD PT-100 Sensors and the liquid

specimen holder. In the set-up, a unidirectional heat flow takes plate across the liquid whose




29

side and three thermocouple readings ( T c1 , T c2 , T c3 i.e. T 4 , T 5 , T 6 on Temperature

Indicator) on the cold side along with the voltmeter (V ) and ammeter ( A) readings.

5. Stop the electric supply to the heater, and continue with the supply of cold water till

there is decrease in temperature of hot plate (may be for another 30-40 min).

6. Open the liquid outlet valve slightly in the downward tilt position and drain the

sample liquid in a receiver, keeping liquid inlet port open.

Specification:

1. Hot Plate

Material = Copper

Diameter = 160 mm

2. Cold Plate

Material = Copper

Diameter = 160 mm

3. Sample Liquid depth = 20 mm

4. Temp. Sensors = RTD PT-100 type.

Type = RTD PT-100 type

Quantity = 6 Nos. No. 1 to No. 3 mounted on hot plate.

No. 4 to No. 6 mounted on cold plate.

5. Digital Temperature indicator

Range = 0°C to 199.9°C

Least Count = 0.1oC

6. Variac = 2 Amp, 230VAC

7. Digital Voltmeter = 0 to 250 Volts

8. Digital Ammeter = 0 to 2.5 Amp.

9. Heater = Nichrome heater 440 Watt




30

Formulae:

1. Heat input Q V I

2. Thermal conductivity of liquid,

( )

h c

X K Q

T T

Hot face average temperature, T h = (T h1 + T h2 +T h3 ) / 3

Cold face temperature, T c = (T c1 + T c2 + T c3 ) / 3

Temperature difference, ΔT = (T h - T c)

Nomenclature:

Q = Heat supplied by heater, W

A = Heat transfer area, m2

T h = Hot face average temperature,OC

T c = Cold face average temperature,OC

∆T = Temperature difference,OC

K = Thermal conductivity of liquid, w/mK

ΔX = Thickness of liquid, m

Exercises:

1. Determine the thermal conductivity of a liquid


1. Use the stabilize A.C. single phase supply only.






volts.



8. Testing liquid should be fully filled.




31

Experiment 8

THERMAL CONDUCTIVITY OF INSULATIING POWDER

Objective:

To determine thermal conductivity of insulating powder

Theory:

Consider the transfer of heat by conduction through the wall of hollow sphere

formed by the insulating powdered layer packed between two thin copper spheres.

Let r i = radius of inner sphere, meter

r o = radius of outer sphere, meter

T i = average temperature of the inner surface, ºC

T o = average temperature of the outer surface, ºC

Where, 1 2 3 4

4i

T T T T T

and 5 6 7 8 9 10

0

6

T T T T T T T

From the experimental values of Q, T i and T o, the unknown thermal conductivity k can be

determined as:

4

o i

o i i o

Q r r k

r r T T

Description:

The apparatus consists of two thin walled concentric spheres of copper of different

size. The small inner copper sphere houses the heating coil. The insulating Powder (Plaster

of Paris) is packed between the two spheres. The power given to the heating coil is

measured by voltmeter and ammeter and can be varied by using dimmerstat. There are ten

(T 1 to T 10) thermocouples embedded on the copper spheres, T 1 to T 4 (4 nos.) are embedded

on the inner sphere and rest T 5 to T 10 (6 nos.) on the outer sphere. Thermal conductivity of

insulating powder can be found out by taking the temperature reading of these




32

thermocouples. Assume that insulating powder is an isotropic material and the value of

thermal conductivity to be constant. The apparatus assumes one-dimensional radial heat

conduction across the powder and thermal conductivity can be determined.


1. Switch on the main power supply 220 AC single phase, 50 Hz.

2. Increase slowly the input to heater by the dimmerstat starting from zero volt position.

3. Adjust input equal to any value between 20 to 60 Watt maximum by voltmeter and

ammeter.

4. Thermocouple readings are taken at frequent intervals (say once in 10 minutes) till

consecutive readings are same indicating that steady state has been reached.

5. Note down the readings in the observation table.

Specification:

Radius of the inner copper sphere, r i = 50 mm

Radius of the outer copper sphere, r o = 100 mm

Voltmeter = 0-300 V

Ammeter = 0-2 ATemperature Indicator = 0-300 ºC.

Dimmerstat = 0-2A, 0-230 V

Heater coil-strip heating element sandwiched between mica sheets

Thermocouples of numbers T 1 to T 4 are embedded on the inner sphere to measure T i

Thermocouples of numbers T 5 to T 10 are embedded on the outer sphere to measure T o

Insulating powder-plaster of paris commercially available powder and packed between the

two spheres.

Formulae:

1. Heat input, Q V I

2. Thermal conductivity of insulating power:




34

Experiment 9

HEAT TRANSFER IN FORCED CONVECTION

Objective:

To find surface heat transfer coefficient between a heated pipe and air flowing

through it by forced convection, for different air flow rates and heat flow rates.

Theory:

Air flowing in to the heated pipe with very high velocity the heat transfer rate

increases. The heat is taken by the cold air from the heat source and rises its temperature.

Thus, for the tube the total energy added can be expressed in terms of a bulk-temperature

difference by

2 1( )

P b bq mC T T

Bulk temperature difference in terms of heat transfer coefficient

q hA T

A traditional expression for calculation of heat transfer in fully developed turbulent flow in

smooth tubes is that recommended by Dittus and Boelter

0.8

0.023Re Pr n

d d Nu

if n = 0.4 for heatingof thefluid

0.3 for coolingof thefluid

Description:

The apparatus consists of blower unit fitted with the test pipe. The test section is

surrounding by nichrome heater. Four Temperature Sensors are embedded on the test

section and two temperature sensors are placed in the air stream at the entrance and exit of

the test section to measure the air temperature. Test Pipe is connected to the delivery side of

the blower along with the Orifice to measure flow of air through the pipe. Input to the

heater is given through a dimmerstat and measured by meters. It is to be noted that only a




35

part of the total heat supplied is utilized in heating the air. A temperature indicator is

provided to measure temperature of pipe wall in the test section. Airflow is measured with

the help of Orifice meter and the water manometer fitted on the board.

Temperature sensors:

T1 = Air inlet temp.

T2, T3, T4, T5 = Surface temp. of test section

T6 = Air outlet temp.


1. Clean the apparatus and make it free from Dust.

2. Put Manometer Fluid (Water) in Manometer connected to Orificemeter.

3. Ensure that all On/Off Switches given on the Panel are at OFF position.

4. Ensure that Variac Knob is at ZERO position, given on the panel.

5. Now switch on the Main Power Supply (220 V AC, 50 Hz).

6. Switch on the Panel with the help of Mains On/Off Switch given on the Panel.

7. Fix the Power Input to the Heater with the help of Variac, Voltmeter and Ammeter

provided.

8. Switch on Blower by operating Rotary Switch given on the Panel.9. Adjust Air Flow Rate with the help of Air Flow Control Valve given in the Air

Line.

10. After 30 Minutes record the temperature of Test Section at various points in each 5

Minutes interval.

11. If Temperatures readings are same for three times, assume that steady state is

achieved.

12. Record the final temperatures.

13. Record manometer reading.




36

Formulae:

1. exp.

( )

a

s a

Qh

A T T

2. 1W

a

H H

3.4

2

oo

1

H g 2d 4

C

Q

Where

dp

do

4. Qa = m C p T

5. m = Q ρa

6. A = Di L

7. Ta = 1 6

2

T T

8. Ts = 2 3 4 5

4

T T T T

Nomenclature:

m = mass flow rate of air, Kg/ sec.

C p = Specific heat of air, J/ Kg C.

T = Temp. rise in air C. (T6 - T1)

ρa = Density of air, kg/ m3

w = Density of water, kg/m3

Q = Vol. flow rate, m3/ sec.

Qa = Heat carried away by air, W

hexp. = experimental value of heat transfer coefficient, W/ m2 0

C

Co = Coefficient of dischargeH = Difference of water level in manometer, m.

d0 = Diameter of Orifice, m

A = Test section area, m2

Ta = Average temperature of air, C

Ts = Average surface temperature, C




37

L = Length of test section, m

Di = I.D. of Test section, m

Exercises:

1. Calculate experimental value of heat transfer coefficient.

2. Calculate theoretical value of heat transfer coefficient.

3. Write your comments on above calculations.


1. Use the stabilize A.C. Single phase supply only.






volts.6. Operate selector switch of temperature indicator gently.







38

Experiment 10

HEAT PUMP TRAINER

Objective:

To determine the coefficient of performance (COP) of heat pump trainer

Theory:

Mechanical Heat Pump is defined as an assembly of different parts of the system

used to produce a specified condition of air within a required space or building. An ideal

system should maintain correct temperature, humidity, air-purity, air-movement and noise

level. Always, it is not possible to maintain all the above factors mentioned and a

compromise should be made to make the system economic.

The main function of the heat pump is to maintain body at a temperature that is

higher than the atmosphere. Though the body may be insulated some heat, say Q H is flowing

out of the body to the atmosphere. Such heat Q H is supplied to the body so that its

temperature is maintained. For this work W is supplied which removes heat Q L from

atmosphere which is at temperature T L and supplies heat Q H to the body.

Q L + W = Q L

Here the heat pump maintains the body at a temperature T H which is higher than

atmospheric temperature T L. For this it does work W .

Description:

The compressor is used for pumping the refrigerant through the system. The

condenser is the forced water-cooled type for which heat exchanger has been provided.

Capillary Tube is provided as an expansion device for evaporator. A temperature indicator

with multi-point selection switch has been provided to get the various temperatures viz.

T1 = Refrigerant Temperature at Suction,0C




39

T2 = Refrigerant Temperature at Discharge,0C

T3 = Refrigerant Temperature before Expansion,0C

T4 = Refrigerant Temperature after Expansion,0C

T5 = Temperature of Water in evaporator tank, 0C

T6 = Temperature of Water out evaporator tank,0C

T7 = Temperature of Water inlet to Condenser,0C

T8 = Temperature of Water outlet of Condenser,0C

The selection of any of the temperature can be made by rotating the selection switch

to the respective channel. We have provided four pressure gauges for indicating R-134(a)

pressures at compressor suction P1, compressor discharge P2, after condenser P3, after

Capillary Tube P4. Energy-meter is provided for measuring power input to the compressor.


1. Switch on mains supply.

2. Switch "ON" the condenser motor and then switch "ON" the compressor.

3. Please do not start the compressor when condenser motor is "OFF". First switch "ON"

the condenser motor and then switch "ON" the compressor.

4. By using selector switch on temperature indicator, note the temperature T1, T2, T3, T4, T5,

T6, T7 and T8 in the observation table.

5. Note the pressures of R-134(a) gas in the circuit by noting pressures P1, P2, P3, and P4 in

the observation table.

6. Note down the energy-meter reading (i.e., time taken in seconds for the wheel to

complete one revolution)

7. Repeat the above procedure to get different sets of readings every 10 minutes till you get

fairly constant temperatures of the consecutive readings. Confirm this by taking one

more set of readings

8. Calculate the COP as per the procedure of calculations given below.

9. Switch off all the switches after you complete the experiment




40

Formulae:

1. COP (Carnot refri) 1

2 1

T

T T

COP (Carnot heat pump) = COP (refri) + 1

Convert the pressure in psi to pressure in Bar (Absolute)

14.8 psi 1 atm

Absolute pressure 1 1/14.8 1 P P

By taking1

P from the chart find the corresponding value of1

T

1

T Saturation temperature at suction pressure

Refer table (Saturated properties of R-134a liquid and vapour)

Similarly find2

P and2

T

2

T Saturation temperature at condenser pressure

2. C.O.P. (Theoretical) 2 3

2 1

h h

h h

Where

h1 = enthalpy for gas at temperature T 1

h2 = enthalpy for gas at temperature T 2

h3= enthalpy for liquid of at temperature T 3

3. C.O.P (actual)Desired output

Required input

C.O.P (actual)Heat transferred to water

Power consumed by the compressor

power consumed by the compressor

pmc T

t

Where

m = mass flow rate of water passing through the condenser




41

2

lph Density of water secm kg/sec

3600 1000

F t

c p = specific heat of water = 4.18 kJ/kg.K

T = temperature difference between T7 and T8 in K.

F 1 = refrigerant flow, LPH

F 2 = water flow through the condenser, LPH

F 3 = water flow through the evaporator, LPH

We can calculate power consumed by the compressor as follows:

Power Consumed (kW) 1

3600 no. of blinks per second3200

Exercises:

1. Determine the coefficient of performance (COP) of heat pump trainer


1. Before operating the system, check the level of water inside the water tank.

2. Do not change settings of LP-HP cut off Valve.

3. Do not touch the charging valve. If this valve gets opened slightly, all refrigerant

will escape leading to non-performance of the instrument.

4. Once the experiment is over, remove water from the water tank.

5. Please do not start the compressor when condenser motor is "OFF". First switch

"ON" the condenser motor and then switch "ON" the compressor.




42

Experiment 11

TO DETERMINE THE COEFFICIENT OF PERFORMANCE (COP) OF

A VAPOUR COMPRESSOR TRAINER

Objective:

To determine the coefficient of performance (COP) of refrigeration trainer

Theory:

In general, refrigeration is defined as any process of heat removal. More specifically,

refrigeration is defined as the branch of science that deals with the process of reducing and

maintaining the temperature of a space or material below the temperature of the

surroundings. The system maintained at the lower temperature is known as refrigerated

system while the equipment used to maintain this lower temperature is known as

refrigerating system.

In accordance with the Clausius’s statement of second law of thermodynamics, heat

does not flow from a low temperature region to high temperature region without the aid of

external energy. This transfer of heat against a reverse temperature gradient can be

accomplished if mechanical energy is supplied to the machine. A machine which maintains

a space at a lower temperature than the surrounding is known as a refrigerator and the

process is known as refrigeration. Refrigeration therefore implies the cooling or removal of

heat from a system. Such cooling may be obtained by any one of the following principles.

i. By chemical means, in which chemical reaction is carried out which absorbsheat for its completion. The heat required for the purpose is taken from the substance

or space to be cooled.

ii. By bringing the substance to be cooled directly or indirectly in contact with

some cooling medium such as chilled water or ice.




43

iii. By using mechanical or heat energy to operate a heat pump by which heat

may be abstracted from a low temperature region and rejected to high

temperature region.

Description:

The refrigeration trainer consists of compressor, condenser, capillary, heater and

water container. The compressor is used for pumping the refrigerant through the system. The

condenser is the forced air-cooled type for which condenser fan and motor has been

provided. Capillary is provided as an expansion device for evaporator. Heater is provided to

change the load on the system. A temperature indicator with multi-point selection switch has

been provided to get the various temperatures viz.

T 1 Refrigerant temperature at suction

T 2 Refrigerant temperature at discharge

T 3 Refrigerant temperature before expansion

T 4 Refrigerant temperature after expansion

T 5 Temperature of water

The selection of any of the temperature can be made by rotating the selection switch to the

respective channel. Four pressure gauges are provided for indicating R-134a pressures at

compressor suction P 1, compressor discharge P 2, after condenser P 3, after thermostatic

expansion P 4.


1. Switch on Mains Supply. Switch on the trainer.

2. By using selector switch on temperature indicator, note the temperature T 1 , T 2 , T 3 , T 4 and

T 5 in the observation table.

3. Note the pressures of R-134a gas in the circuit by noting pressures P 1 , P 2 , P 3 , P 4 in the

observation table.




45

Where

m = mass of water

c p = specific heat of water = 4.18 KJ/Kg.K

T = temperature difference in T 5 over a period of time ‘t’ (sec)

We can calculate power consumed by the compressor as follows:

Power Consumed (Kw) 1

3600 no. of blinks per second3200

Exercises:

1. Determine the coefficient of performance (COP) of refrigeration trainer


1. Before operating the system, check the level of water inside the Water Tank (i.e. the

Refrigerated Space). Water should be filled up to the marked level.

2. Do not start the compressor when condenser motor is "OFF". First switch "ON" the

condenser motor and then switch "ON" the compressor.

3. Do not change settings of LP-HP cut off Valve.

4. Do not run agitator motor for a period more than 15 min continuously. Turn it off for

a few minutes and then start it again. This allows proper cooling of the agitator

motor.

5. Do not touch the charging valve. If this valve is opened slightly, the entire

refrigerant will leak leading to non-performance of the instrument.

6. Once the experiment is over, remove water from the water tank so as to prevent

rusting of any parts inside the test chamber.




46

Experiment 12

VAPOR ABSORPTION REFRIGERATION TRAINER

Objective:

To determine the coefficient of performance (COP) of vapor absorption refrigeration trainer

Theory:

The function of the compressor in the vapor-compression system is to continuously withdraw

the refrigerant vapor from the evaporator and to raise its temperature and pressure so that the heat

absorbed in the evaporator, along with the work of compression may be rejected in the condenser.

In the vapor-absorption system the function of the compressor is accomplished in a three

step process by the use of the absorber, pump and generator as follows

(i) Absorber: Absorption of the refrigerant vapor by its weak or poor solution in a suitable

absorbent or adsorbent, forming a strong or rich solution.

(ii) Pump: Pumping of the rich solution raising its pressure to the condenser pressure.

(iii) Generator: Distillation of the vapor from the rich solution leaving the poor solution for

recycling.

Description:

The simple vapor absorption trainer consists of a condenser as an expansion device and an

evaporator as in the vapor-compression system. In addition, absorber, pump, generator and a

pressure reducing valve to replace the compressor.

The flow of fluids in the system is described as follows

1. Vertical boiler in which an aqua solution of ammonia can range itself from distilled water at

the bottom of the boiler to strong ammonia vapor at the surface of the liquid.

2. A water separator which is provided to remove water vapor so that they should not enter the

condenser, get condensed there and pass on to evaporator where chocking might occur due to

its freezing. The water vapor is formed in the boiler as some of the water may evaporate on




47

application of heat to the boiler. The separator is jacketed with liquid ammonia at a pressure

of about 14 bar gauge for which the saturation temperature is about 40C.

3. The dehydrated ammonia gas gets condensed to liquid in the condenser and gravitates to ‘U’

tube which acts as seal for a gas to enter the evaporator, or any gas passing from evaporator to

the condenser.

4. In the evaporator, the ammonia liquid comes across an atmosphere of hydrogen at about 12

bar gauge. The plant is charged to a pressure of about 14 bar. Hence due to Dalton’s law of

partial pressure, the pressure of ammonia gas should fall to about 2 bar gauge and the

saturation temperature corresponding to about 2 bar is about 10C. The temperature

surrounding the evaporator is much higher than this. Thus ammonia evaporates and produces

the refrigerating effect i.e. absorbs the latent heat of vaporization at 2 bar gauge and about -

10C from the space to be refrigerated.

5. In order to ensure continuous action, hydrogen gas has to be removed from ammonia vapor.

This is done in the absorber where a descending spray of very dilute ammonia liquid meets

the ascending mixture of ammonia vapor and hydrogen. Ammonia vapor is readily absorbed

with evaluation of heat so that absorber has to be water jacketed or air cooled, otherwise

evaporation may take place in this unit and the absorption may cease.

6. Heat exchanger: liquid heat exchanger is placed in between absorber and the generator. This

week liquid gets cooled and strong liquid gets heated. Thus heat is economized and better

thermal efficiency obtained. This heat exchanger is counter-flow type. The strong solution

from the absorber is preheated on its way to generator or boiler, and the dilute solution on its

way to absorber is cooled. This cooling of weak liquid also helps absorption and reduces the

cooling of absorber by external source.

A gas heat exchanger is used between the absorber and the evaporator. The hydrogen gas

going to the evaporator gets cooled by the cool ammonia vapor and hydrogen gas mixture.

7. It may be noted that the circulation is effected by gravity and thus no moving part in the

system is necessary.




48


For electrical input to the system

1. Connect water supply and drain pipes.

2. Switch on the supply to the refrigeration circuit.

3. Take the “Selector” switch on the panel to “Electrical” position.

4. Take the Fuel Selector switch to “I” position.

5. Ensure that Thermostat is set to “3.”

6. Note all the readings of the temperatures T1, T2, T3 …….T6 on the temperature indicators

and power on the power indicator.

7. Wait for approximately 45 min and start the water supply. Adjust the supply to be

between 2 to 3 lph. To set the water flow rate, there is a valve provided near the point

where there is water inlet connection.

8. Note the readings in the observation table every 10 min.

9. Take the readings till the system stabilizes. This is indicated by constant reading of the

outlet water over two subsequent readings.

For LPG input to the system

1. Connect water supply and drain pipes.

2. Switch on the supply to the refrigeration circuit.

3. Take the “Selector” switch on the panel to “LPG” position.

4. Take the fuel selector switch to LPG position. (There is an icon of flame to indicate

LPG).

5. Ensure that thermostat is set to “3.”

6. Ensure that the flow control knob on the LPG rotameter is fully open.

7. Note all the readings of the temperatures T1, T2, T3, T4, T5 and T6 on the

temperature indicators and power on the power indicator.

8. Fire the refrigerator. To fire the refrigerator,

Ensure that the LPG is properly and correctly connected to the kit.

Ensure that the LPG rotameter knob is fully open.




49

At the bottom panel of the trainer there are two buttons, next to the Thermostat

knob. Keep the button marked “PUSH1” pressed. While keeping this pressed,

press the button marked “PUSH2”.

Observe the flame in the window provided for this.

Once you observe the flame, leave the button “PUSH1”

You may have to press the button “PUSH2” multiple times in succession toobtain flame.

9. Wait for approximately 45 min and start the water supply. Adjust the supply to be

between 2 to 3 lph. To set the water flow rate, there is a valve provided near the

point where there is water inlet connection.

10. Note the readings in the observation table every 10 min. Refer sample observation

table enclosed.

11. Take the readings till the system stabilizes. This is indicated by constant reading of

the outlet water over two subsequent readings.

Formulae:

For electrical input to the system

1. To find COPactual

lph Density of water sec

m kg/sec3600 1000

V t

5 6

kg kJ(W) ( - ) K 1000

s Kg KQ m Cp T T

Cp = Specific heat of water = 4.186 KJ/ kg-K

Actual

(W)COP

(W)in

Q

P

2. To find COPideal

ideal

COP g ae

c e g

T T T

T T T




50

For LPG input to the system

1. To find COPactual

lph Density of water sec

m kg/sec 3600 1000

V t

5 6

kg kJ(W) ( - ) K 1000

s Kg KQ m Cp T T

Cp = Specific heat of water = 4.186 KJ/ kg-K

Actual

(W)COP

(W)in

Q

P

in

kg hr KJP W Calorific Value of LPG

3600 kgin

G

Calorific Value of LPG = 50000 KJ/kg

2. To find COPideal

g

ag

ec

eIdeal

T

TT

TT

TCOP

Nomenclature:

T 1 = evaporator temperature (T e)

T 2 = chamber temperature

T 3 = condenser temperature (T c)

T 4 = absorber temperature (T a)

T 5 = temperature of water inlet (T ci)

T 6 = temperature of water outlet (T co) T 7 = generator temperature (T g )

Exercises:




52

Experiment 13

AIR CONDITIONING TRAINER

Theory:

An Air Conditioning System is defined as an assembly of different parts of the

system used to produce a specified condition of air within a required space or building. An

ideal air-conditioning system should maintain correct temperature, humidity, air-purity, air

movement and noise level. Always, it is not possible to maintain all the above factors

mentioned and a compromise should be made to make the system economic.

The air-conditioning systems are mainly classified as:

1. Central station air-conditioning system.

2. Unitary air-conditioning system.

3. Self-contained air-conditioned units.

Central Station Air-Conditioning System

In a central air-conditioning system, all the components of the system are grouped

together in one central room and conditioned air is distributed from the central room to therequired places through extensive duct work.

The central air-conditioning system is generally used for the load above 25 tons of

refrigeration and 2500 m3/min. of conditioned air.

Unitary Air-Conditioning System

All the components of the unitary air-conditioned system are assembled in the

factory itself. These assembled units are usually installed in or immediately adjacent to a

zone or space to be conditioned. It is commonly preferred for 15 tons capacity or above or

around 200 m3/min. of air flow. Recently even 100 tons capacity units are also

manufactured.

Self-contained Air-conditioning Units

Self-contained units are available in wide variety of sizes and for many specific

purposes. The following three types are commonly available in the market.

a. Room cooler




54

T1 – Refrigerant temperature at suction.

T2 – Refrigerant temperature at discharge.

T3 – Refrigerant temperature before expansion.

T4 – Refrigerant temperature after expansion.

T5 – Dry bulb temperature of air at suction.

T6 – Dry bulb temperature in chamber.

T7 – Wet bulb temperature in chamber

The selection of any of the temperature can be made by rotating the selection switch

to the respective channel.

We have provided pressure gauges for indicating gas pressures at compressor suction

P1, compressor discharge P2, after condenser P3, after thermostatic expansion valve

P4.

An energy meter provided for measuring power input to compressor.

We have supplied a steamer to generate the steam or hot water as per the

requirements of the experiment. Steam piping has been done to enable the user to

inject steam in air inlet duct and / or test cabin.




57

Experiment No: 13b

Objective:

To determine the coefficient of performance (COP) of air conditioning system in air

re-circulation type ducting.

Air Damper Position:

Air inlet damper Closed 100%

Air outlet damper Closed 100%

Air circulation damper Open 100%


1. Keep the status of air damper positions and expansion device status as given above.

2. Switch on mains switch and compressor supply.

3. By using selector switch on temperature indicator, note the temperature T1, T2, T3, T4,

T5, T

6, and T

7in the observation table.

4. Note the pressures of refrigerant gas in the circuit by noting P1, P2, P3, P4 pressures in the

observation table.

5. Repeat the above procedure to get different sets of readings till you get fairly constant

pressures of the consecutive readings. Confirm this by taking one more set of readings.

6. Calculate the COP as per the procedure of calculations given below.

7. Switch off all the switches after you complete the experiment.

Formulae:

1. C.O.P (Reversed Carnot) 1

2 1

T

T T

Convert the pressure in psi to pressure in Bar (Absolute) 14.8 psi 1 atm

Absolute pressure 1 1/14.8 1 P P




58

By taking1

P from the chart find the corresponding value of1

T

1T Saturation temperature at suction pressure

Refer table (Saturated properties of R-134a liquid and vapour)

Similarly find2

P and2

T

2

T Saturation temperature at condenser pressure

2. C.O.P (Theoretical) 1 4

2 1

h h

h h

Where,

h1 = enthalpy (for gas) at temperature T 1

h2 = enthalpy (for gas) at temperature T 2

h4 = enthalpy (for liquid) at temperature T 4

Exercises:

1. Determine the Coefficient of Performance (COP) of air conditioning system in air re-

circulation type ducting.




60

Experiment No: 13d

Objective:

Study of dehumidification




Air re-circulation damper Open 100%


1. Keep the status of the damper and expansion device selection as given above.

2. Switch on Mains switch.

3. Note the initial reading of WBT & DBT in the test cabin that is T6 and T7 respectively.

4. Switch on the Steamer. Observe that the wet bulb temperature changes as the steam is

introduced. Note the readings.

5. Switch on the compressor. Switch off the steamer.

6. The temperature T6 will start dropping.

7. Start noting the WBT/DBT in the test chamber when the DBT or T6 drops down by, say

100

C

8. Note the DBT and WBT of the test-chamber, that is, T6 and T7 respectively, every 5

minutes.

9. Switch off all the switches after you complete the experiment.

10. Study the observation table & note that the air is dehumidified due to due point cooling.

Exercises:

1. Study the dehumidification process and write the remarks




61

Experiment No: 13e

Objective:

To study the summer air conditioning


Air inlet damper Open partially

Air outlet damper Open partially

Air re-circulation damper Closed partially

Experimental Procedure: -

1. Keep the status of the damper and expansion device selection as given above.

2. Switch on mains switch and heater.

3. Note the temperature of DBT/WBT in the controlled cabin that is, T6 and T7

respectively.

4. Take DBT/WBT readings every 5 minutes.

5. See that the T6 increases. Adjust this to 350C approximately.

6. Switch on the compressor.

7. Observe the temperature T6 and T7 till T6 goes to 280C.

8. Switch off all the switches after you complete the experiment

Exercises:

1. Study the summer air conditioning and write the remarks




62

Experiment 14

PARALLEL AND COUNTER FLOW HEAT EXCHANGER

Objective:

To determine log mean temperature difference (LMTD), overall heat transfer

coefficient based on inner tube diameter and effectiveness of the heat exchanger for different

flow rates of hot and cold water.

Theory:

The process of heat exchange between two fluids that are at different temperatures

and separated by a solid wall occurs in many engineering applications. The device used to

implement this exchange is termed a heat exchanger , and specific applications may be found

in space heating and air-conditioning, power production, waste heat recovery, and chemical

processing.

The simplest type of heat exchanger consists of two concentric pipes of different

diameters, called the double-pipe heat exchanger. One fluid in a pipe heat exchanger flows

through the smaller pipe while the other fluid flows through the annular space between the

two pipes. Two types of flow arrangement are possible in a double-pipe heat exchanger: in parallel flow, both the hot and cold fluids enter the heat exchanger at the same end and move

in the same direction. In counter flow, on the other hand, the hot and cold fluids enter the

heat exchanger at opposite ends and flow in opposite directions.

The exchange of heat takes places in between hot water which coming from geyser

and cold water. Inlet and outlet temperature is measured from temperature sensor, which

directly shows on temperature indicator. In this heat exchanger it is require to take discharge

at outlet from heat exchanger less than or equals to the rotameter reading.

Description:

Experimental setup consist of following parts

Heat exchanger (tube-in-tube type):

1500mm length, outer tube diameter 41 mm, inner copper tube diameter 10.7 mm

Geyser:

Capacity 3 lit, Wattage 3 KW, automatically trip at 80OC, make- OSHAM




63

Rotameter:

60 to 600 LPH.

Pump:

1900 LPH for this head, 0.25 HP.

Temperature indicator:

Digital temperature indicator having range 0 to 400OC, make- EUTECH

Electronic energy meter:

Energy meter constant- 3200 imp/ KWh.


Before starting the trainer, follow the following start up procedure.

1. Ensure that supply voltage is 230 V in your laboratory.

2. On the main supply so that temperature indicator becomes ON.

3. ON the hot water pump so that water starts flowing through the geyser.

4. ON the geyser so that it start to heat water.

5. Now start cold water supply.

6. Adjust the flow of cold and hot water supply by valves.

7. Ensure rotameter shows the constant reading (flow in LPH).8. Wait until steady state temperature will reach.

9. After steady state temperature reaches, take the readings as per observation table.

10. During first step, copper matrix absorbs the heat from hot water and during next step;

it gives heat to the cold water.

11. Measure the temperature as per observation table given.

Formulae:

1. The log mean temperature difference (LMTD), lmT , for the counter-flow heat

exchanger

, , , , 1 3 2 4

1 3, ,

2 4, ,

lnln

h i c o h o c i

lm

h i c o

h o c i

T T T T T T T T T

T T T T

T T T T

Where,




64

For counter flow:

T 1 = inlet temperature of hot water,OC

T 2 = outlet temperature of hot water,OC

T 4 = inlet temperature of cold water, OC

T 3 = outlet temperature of cold water,OC

2. Effectiveness of the heat exchanger,

, , 3 4

ax min 1 4min , ,

c c o c i c

h i c i

C T T C T T q

q C T T C T T

Where,

q = actual heat transfer rate for a heat exchanger

qmax = maximum possible heat transfer possible

min

heat capacity rate of hot fluid

heat capacity rate of cold fluid

h h ph

c c pc

h c

C m c

C m c

C C or C

3. The overall convection coefficient based on inner tube diameter, U i

ln /1 1 1 1 1

2ln /1 1 1

2 2

o i

i i o o i i t o o

o i i i

i i t t o o

D D

UA U A U A h A k L h A D D D D

U h k k L h D

For hot water flow through the tube of diameter, Di

If the Reynolds number,4

Re 2300h D

i

m

D

then the flow is laminar.

For laminar flow, 3.66 i i D

h D Nu

k

For the cold water flow through the annulus of hydraulic diameter Dh

If

, 2 2

4 4Re 2300

o i m h c c D h

o i o i

D Du D m m

D D D D

then the

flow is laminar.

For laminar flow through the annulus,

6.6 o o i o h

D

h D Dh D Nu

k k




65

, , , ,

, , , , 1 2

( ) or ( )

( ) ( )

( ) ( )

h p h h i h o i i lm CF i i lm

h p h h i h o h p h

i

i lm i lm

q m c T T q U A T U D L T

m c T T m c T T U

D L T D L T

Where,

q = heat transfer rate, W/m2

k t = thermal conductivity of copper tube, W/m

2.K

k = thermal conductivity of water, W/m2.K

hm = mass flow rate of hot water, kg/s

hm

= mass flow rate of cold water, Kg/s

U i = overall convection coefficient based on inner tube diameter, W/m2.K

Di = diameter of the inner tube (copper)

Do = diameter of the outer tube

L = length of the pipe

Exercises:

1. Determine log mean temperature difference (LMTD).

2. Overall heat transfer coefficient based on inner tube diameter.

3. The effectiveness of the heat exchanger for different flow rates of hot and cold

water.


1. Don’t hold or play with red painted tube.

2. Don’t start the pump without water in the sump.

3. Don’t start the geyser without water supply.

4. Keep all the experimental set up undisturbed.

5. Don’t pull out the thermocouple connections.





66

Experiment 15

SHELL AND TUBE HEAT EXCHANGER

Objective:

To determine log mean temperature difference (LMTD), average convection

coefficient based up on the outside area of the tube and the effectiveness of the heat

exchanger for different flow rates of hot and cold water.

Theory:

Heat exchangers are devices that facilitate the exchange of heat between two fluids

that are at different temperatures while keeping them from mixing with each other. Heat

exchangers are commonly used in practice in a wide range of applications, from heating and

air-conditioning systems in a household, to chemical processing and power production in

large plants. Heat exchangers differ from mixing chambers in that they do not allow the two

fluids involved to mix.

Perhaps the most common type of heat exchanger in industrial applications is the

shell-and-tube heat exchanger. It contain a large number of tubes packed in a shell with their

axes parallel to that of the shell. Heat transfer takes place as one fluid flows inside the tubes

while the other fluid flows outside the tubes through the shell.

Baffles are usually installed to increase the convection coefficient of the shell-side

fluid by inducing turbulence and a cross-flow velocity components. In addition, the baffles

physically support the tubes, reducing flow-induced tube vibration.

Description:

Experimental setup consist of following parts

Shell and tube type heat exchanger:

300mm length and 150 mm diameter, copper tubes- 55 numbers of size 9.6 mm (ID)

and 12 mm (OD).




67

Geyser:

Capacity 3 lit, Wattage 3 kW, automatically trip at 80OC, make- OSHAM

Rotameter:

60 to 600 LPH.

Pump:

1900 LPH for this head, 0.25 HP.

Temperature indicator:

Digital temperature indicator having range 0 to 400OC, make- EUTECH

Electronic energy meter:

Energy meter constant- 3200 imp/ kWh.


Before starting the trainer, follow the following start up procedure

1. Ensure that supply voltage is 230 V in your laboratory.

2. On the main supply so that temperature indicator becomes ON.

3. ON the hot water pump so that water starts flowing through the geyser.

4. ON the geyser so that it start to heat water.

5. Now start cold water supply.6. Adjust the flow of cold and hot water supply by valves.

7. Ensure rotameter shows the constant reading (flow in LPH).

8. Wait until steady state temperature will reach.

9. After steady state temperature reaches, take the readings as per observation table.

10. During first step, copper matrix absorbs the heat from hot water and during next step;

it gives heat to the cold water.

11. Measure the temperature as per observation table given.

Formulae:

1. Shell and tube exchanger with one shell and one tube pass approximates a parallel flow

heat exchanger. The log mean temperature difference (LMTD),lm

T , for the parallel

flow heat exchanger




68

, , , , 1 3 2 4

1 3, ,

2 4, ,

lnln

h i c i h o c o

lm

h i c i

h o c o

T T T T T T T T T

T T T T

T T T T

Where,

For parallel flow:

T 1 = inlet temperature of hot water,OC

T 2 = outlet temperature of hot water,OC

T 3 = inlet temperature of cold water,OC

T 4 = outlet temperature of cold water,OC

2. Effectiveness of the heat exchanger,

, , 4 3

ax min 1 3min , ,

c c o c i c

h i c i

C T T C T T q

q C T T C T T

Where,

q = actual heat transfer rate for a heat exchanger

qmax = maximum possible heat transfer possible

min

heat capacity rate of hot fluid

heat capacity rate of cold fluid

h h ph

c c pc

h c

C m c

C m c

C C or C

3. Average convection coefficient based up on the outside area of the tube, ho

The heat transfer rate, q

, , ,

, , , , 1 2

( ) or ( )

( ) ( )

( ) ( )

h p h h i h o i i lm i lm

h p h h i h o h p h

i

i lm i lm

q m c T T q U A T U N D L T

m c T T m c T T U

N D L T N D L T

The overall convection coefficient, U i based on inner tube diameter

ln /1 1 1 1 1

2

1 1 1ln /

2

o i

i i o o i i t o o

i i o i

i i t o o

D D

UA U A U A h A k L h A

D D D D

U h k h D

For hot water flow through the tube of diameter, Di



Tear- off

Sheets



Tear off sheet: 1

Experiment 1

HEAT TRANSFER THROUGH LAGGED PIPE

Objective:

To determine heat flow rate through the lagged pipe for known value of thermal

conductivity of lagging material and get the combined thermal conductivity of lagging

material. Plot the temperature distribution across the lagging material.

Observations:

1. Radius of innermost pipe, r i = 25 mm

2. Radius of middle pipe , r m = 50 mm

3. Radius of outermost pipe, r 0 = 75 mm

4. Material filled in inner annulus = asbestos

5. Material filled in outer annulus = sawdust

6. Thermal conductivity of asbestos, k 1 = 0.26 W/moC

7. Thermal conductivity of sawdust, k 2 = 0.069 W/moC

8. Length of the lagged pipe, L = 1000 mm

Observation Table:

Sr. No.

V(V) I (A)

Heat Supplied

Q =V I

(W)

Thermocouple Readings (0C)

T1 T2 T3 T4 T5 T6

Results:

1. The heat input, Q Exp =

2. The value of combined thermal conductivity of lagging material, k eff. =

Graph: Plot temperature profile.



Tear off sheet: 1

Experiment 2

STEFAN BOLTZMANN APPARATUS

Objective:

To study radiation heat transfer by a black body hence finds the Stefan

Boltzmann constant.

Observations:

1. Mass of test disc = 0.0051 kg

2. Specific heat of disc material = 0.418 kJ/kg C

3. Hemispherical enclosure dia = 200 mm4. Base plate, Bakelite diameter = 250 mm.

5. Test disc dia (dD) = 20 mm

6. Temp. Hemisphere (Th) = _______ K

7. Temp. Of disc at time t= 0 (TD) = _______ K

8. From the graph (dT/dt) at t = 0 = _______ C/sec.

Observation Table:

Time t (sec.) Temperature (T) of disc in ºC

Results:

1. σ =

2. Comments:



Tear off sheet: 1

Experiment 3

EMISSIVITY MEASUREMENT APPARATUS

Objective:

To find out the emissivity of a test plate.

Observations:

1. Test plate dia = 160 mm

2. Black plate = 160 mm

3. Stefan Boltzmann Constant, = 5.670 10-8 W/ m² K 4

Observation Table:

Black plate:

Voltage, V Amperage, I Power input, W b = V I

(W)

Black plate temp, T b (oC)

Test plate:

Voltage, V Amperage, I Power input, W s = V I

(W)

Test plate

temperature

T t (oC)

Ambient

temperature

T s (oC)

Results:

Emissivity of the test plate, εt =



Tear off sheet: 1

Experiment 4

HEAT TRANSFER IN NATURAL CONVECTION

Objective:

To find out the heat transfer co-efficient of vertical cylinder in natural

convection.

Observations:

1. Outer diameter of Cylinder, d = 35 mm.

2. Length of Cylinder, L = 500 mm.

3. Input to heater = V I (W)

Where

V = Volts.

I = Amps.

Observation Table:

Run No. V

(Volts)

I

(Amp)

T1

(oC)

T2

(oC)

T3

(oC)

T4

(oC)

T5

(oC)

T6

(oC)

T7

(oC)

T8

(oC)

Results:

The heat transfer coefficient, h =



Tear off sheet: 1

Experiment 5

DROPWISE AND FILM CONDENSATION

Objective:

To find the heat transfer coefficient for drop wise condensation and film

condensation process.

Observations:

1. Outer diameter of heat transfer surface, Do = 20 mm

2. Inner diameter of heat transfer surface, Di = 17 mm

3. Length of heat transfer surface, L = 160 mm

4. Inside heat transfer area, Ai = 0.008549 m2

5. Outside heat transfer area, Ao = 0.010057 m2

6. Heat of evaporation, = 2257 kJ/kg

Observation Table:

Condenser under Test

S.N. Water flow

rate (LPH)

Steam

condensed (ml)

Time

(min)Temperature

T1(

oC)

T2(oC)

T3(oC)

T4(

oC)

T5(oC)

Properties of water at bulk mean temperature of water i.e. (T5 +T6)/2

7. Specific heat of water, CP = __________ kJ/kgK

8. Density of water, 1 = __________ kg/m3

9. Kinematics Viscosity, 1 = __________ m2/sec

10. Viscosity of water, μ = __________ N.s/m2



Tear off sheet: 2

11. Thermal conductivity, k 1 = __________ W /m K

Properties of water at bulk mean temperature of water i.e. (T3 +T4)/2

12. Density of water, 2 = __________ kg/m3

13. Viscosity of water, μ = __________ N.s/m2

14. Thermal conductivity, k 2 = __________ W /m K

Results:

Mass flow

rate of water

M w(Kg/s)

Rate of Steam

condensed

M s(Kg/s)

Calculated heat transfer

coefficient (2

W/m K )

Experimental heat

transfer coefficient

(2

W/m K )ho hi U ho hi U



Tear off sheet: 1

Experiment 6

HEAT TRANSFER FROM A PIN FIN

Objective:

To study the temperature distribution along the length of a pin fin under free and

forced convection heat transfer and find the fin efficiency.

Observations:

1. Diameter of the fin, D = 12.7 mm

2. Length of the fin, L = 125 mm

3. Diameter of the orifice, d o = 39 mm

4. Inner diameter of the delivery pipe, d P = 52 mm

5. Coefficient of discharge (Orifice meter), C o = 0.64

6. Thermal conductivity of fin material (Brass), k f = 110 W/ m K

Observation Table:

Experiment Power

input

V I

Fin temperature, oC Ambient

air temp,

oC

T f = T 6

Manometer

Reading,

h

m of water

T 1

( x

=2.5

cm)

T 2

( x = 5

cm)

T 3

( x =

7.5

cm)

T 4

( x =

10

cm)

T 5

( x =

12.5

cm)

Free

convection

Forced

convection

Results:

1. Fin efficiency, =

2. Fin effectiveness =

Graph:

Plot the temperature profile within the fin T Vs x



Tear off sheet: 1

Experiment 7

THERMAL CONDUCTIVITY OF LIQUIDS

Objective:

To determine the thermal conductivity of a liquid

Observations:

1. Diameter of the hot plate = 160 mm

2. Diameter of the cold plate = 160 mm

3. Sample Liquid depth, X

= 20 mm

Observation Table:

S.

No.

V

(Volt)

I

(amp)

T h1

(oC)

T h2

(oC)

T h3

(oC)

T C1

(oC)

T C2

(oC)

T C3

(oC)

Cold water

flow rate

Results:1. Sample liquid = _________

2. Heat input, Q = _________ W

3. Thermal conductivity of liquid, K = _________W/m.K



Tear off sheet: 1

Experiment 9

HEAT TRANSFER IN FORCED CONVECTION

Objective:

To find surface heat transfer coefficient between a heated pipe and air flowing through it

by forced convection, for different air flow rates and heat flow rates.

Observations:

1. Length of test section (L) = 0.412 m

2. I.D. of Test section (Di) = 0.032 m

3. O.D. of Test Section (D0) = 0.038 m4. Orifice Diameter (d0) = 0.014 m

5. Orifice pipe inside diameter (dP) = 0.028 m

6. Coefficient of discharge (C0) = 0.6

7. Density of water (ρW) = 1000 kg/m3

8. Density of air (ρa) = 1.205 kg/m3

9. Manometer reading (H) = ________ m

Observation Table:

Results:

1. hexp. =

2. hthe =

3. Comments:

Sr. No.V

(VOLT)

I

(AMPS)

T1

(0

C)

T2

(0

C)

T3

(0

C)

T4

(0

C)

T5

(0

C)

T6

(0

C)

Manometer

Reading (m.)

h1 h2



Tear off sheet: 1

Experiment 10

HEAT PUMP TRAINER

Objective:

To determine the coefficient of performance (COP) of heat pump trainer

Observations:

1. Specific heat of water, C p = 4.18 kJ/kg.K

Observation Table:

No T1

0C

T2

0C

T3

0C

T4

0C

T5

0C

T6

0C

T7

0C

T8

0C

P1

P.S.I

P2

P.S.I

P3

P.S.I

P4

P.S.I

F1

LPH

F2

LPH

F3

LPH

1 400 300

2 450 350

3 500 400

4 550 450

5 600 500

Results:

F2

LPH

F3

LPH

C.O.P (Reversed Carnot) C.O.P (Theoretical) C.O.P (Actual)

400 300

450 350

500 400

550 450

600 500



Tear off sheet: 1

Experiment 11

TO DETERMINE THE COEFFICIENT OF PERFORMANCE (COP)

OF A VAPOUR COMPRESSOR TRAINER

Objective:

To determine the coefficient of performance (COP) of refrigeration trainer

Observations:


Observation Table:

Obs

no.

T 1

0C

T 2

0C

T 3

0C

T 4

0C

T 5

0C

P 1

P.S.I

P 2

P.S.I

P 3

P.S.I

P 4

P.S.I

Energy meter

No. of blinks

per minute

1

2

3

4

5

67

Results:

T C.O.P (Reversed Carnot) C.O.P (Theoretical) C.O.P (Actual)



Tear off sheet: 1

Experiment 12

VAPOR ABSORPTION REFRIGERATION TRAINER

Objective:

To determine the coefficient of performance (COP) of vapor absorption

refrigeration trainer

Observations:


2. Calorific Value of LPG = 50000 KJ/kg

Observation Table:

Temp. of

evaporator

Te (C)

Temp. of

water inlet

Tci (C)

Temp.

water out

Tco (C)

Temp. of

absorber

Ta (C)

Temp.

generator

Tg (C)

Temp. of

condenser

Tc (C)

Volume

V (lph)

Time

t (sec)

Power output

Pin (W)

Gas consumption

Gin (kg/hr)

Results:

COPactual COPideal



Tear off sheet: 1

Experiment 13

AIR CONDITIONING TRAINER

Experiment No: 13a

Objective:

To determine the Coefficient of Performance (COP) of air conditioning system in

open type Ducting


Air inlet damper Open 100%

Air outlet damper Open 100%

Air circulation damper Closed 100%

Observation Table:

Ob

No.

T1

0C

T2

0C

T3

0C

T4

0C

T5

0C

T6

0C

T7

0C

P1

P.S.

I

P2

P.S.

I

P3

P.S.

I

P4

P.S.

I

Load

kw

Ref.

Flow

1

23

4

5

Observation No. C.O.P (reversed Carnot) C.O.P (Theoretical)

1

2

3

4

5

Remarks:



Tear off sheet: 2

Experiment No: 13b

Objective:

To determine the coefficient of performance (COP) of air conditioning system in

air re-circulation type ducting.




Air circulation damper Open 100%

Observation Table:

Ob

No.

T1

0C

T2

0C

T3

0C

T4

0C

T5

0C

T6

0C

T7

0C

P1

P.S.

I

P2

P.S.

I

P3

P.S.

I

P4

P.S.

I

Load

kw

Ref.

Flow

1

2

3

4

5

Observation No. C.O.P (reversed Carnot) C.O.P (Theoretical)

1

2

3

45

Remarks:



Tear off sheet: 3

Experiment No: 13c

Objective:

To study the humidification process





Observation Table:

Observation

No.

Time

hh : mm

T6

OC

T7

OC

Relative

Humidity

1

2

3

4

5

Remarks:



Tear off sheet: 4

Experiment No: 13d

Objective:

Study of dehumidification





Observation Table:

Observation

No.

Time

hh : mm

T6

OC

T7

OC

Relative

Humidity

1

2

3

4

5

Remarks:



Tear off sheet: 5

Experiment No: 13e

Objective:

To study the summer air conditioning


Air inlet damper Open partially

Air outlet damper Open partially

Air re-circulation damper Closed partially

Observation Table:

Observation

No.

Time

hh : mm

T6

OC

T7

OC

1

2

3

4

5

Remarks:



Tear off sheet: 1

Experiment 14

PARALLEL AND COUNTER FLOW HEAT EXCHANGER

Objective:

To determine log mean temperature difference (LMTD), overall heat transfer

coefficient based on inner tube diameter and effectiveness of the heat exchanger for

different flow rates of hot and cold water.

Data:

1. diameter of outer tube ( Do) = 41 mm

2. diameter of inner tube ( Di) = 10.7 mm

3. length of the tube ( L) = 1500 mm

4. thermal conductivity of the inner tube (k t ) = 400 W/m.K

Observation Table:

1. Cold water flow rate (C

m ):_______LPH

Hot water flow rate (h

m ):_______LPH

SR

NO.

T 1OC

T 2OC

T 3OC

T 4OC

LMTD

lmT

Effectiveness

Overall heat transfer

coefficient

U i

1 46

2 49

3 52

4 55


m ):_______LPH


m ):_______LPH



Tear off sheet: 1

Experiment 15

SHELL AND TUBE HEAT EXCHANGER

Objective:

To determine log mean temperature difference (LMTD), average convection

coefficient based up on the outside area of the tube and the effectiveness of the heat

exchanger for different flow rates of hot and cold water.

Data:

1. diameter of the shell ( D) = 150 mm

2. inner diameter of the tube ( Di) = 9.6 mm

3. outer diameter of the tube ( Do) = 12 mm

4. length of the tube ( L) = 1500 mm

5. number of tubes ( N ) = 55

6. thermal conductivity of the tube (k t ) = 400 W/m.K

Observation Table:

1. Cold water flow rate ( C m ):_______LPH


m ) :_______LPH

SR

NO.

T 1OC

T 2OC

T 3OC

T 4OC

LMTD

lmT

Effectiveness

Average convection

coefficient

ho

1 46

2 49

3 52

4 55




m ):_______LPH


m ):_______LPH

SR

NO.

T 1OC

T 2OC

T 3OC

T 4OC

LMTD

lmT

Effectiveness

Average convection

coefficient

ho

1 46

2 49

3 52

4 55


m ):_______LPH


m ):_______LPH

SR

NO.

T 1OC

T 2OC

T 3OC

T 4OC

LMTD

lmT

Effectiveness

Average convection

coefficient

ho

1 46

2 49

3 52

heat transfer lab manual 2015-16

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