design of shell and tube heat exchanger using ... · pdf filedesign of shell and tube heat...

Research Journal of Engineering Sciences ___________________________________________ ISSN 2278 – 9472

Vol. 3(7), 8-16, July (2014) Res. J. Engineering Sci.

International Science Congress Association 8

Design of Shell and Tube Heat Exchanger Using Computational Fluid

Dynamics Tools Arjun K.S. and Gopu K.B.

Department of Mechanical Engineering, Manav Bharti University, Solan, INDIA

Available online at: www.isca.in, www.isca.me Received 29th April 2014, revised 9th June 2014, accepted 11th July 2014

Abstract

When the helix angle was varied from 00 to 20

0 for the heat exchanger containing 7 tubes of outer diameter 20 mm and a

600 mm long shell of inner diameter 90 mm, the simulation shows how the pressure vary in shell due to different

helix angle and flow rate. The heat transfer coefficient when recorded showed a very high value when the pressure inside

the heat exchanger registered a decline value and this incremental hike was found to be highly significant in the present

study. This might be due to the rotational and helical nature of flow pattern following the geometry change by the

introduction of continuous helical baffles in the shell side of the heat exchanger. The simulation results obtained with

Computational fluid dynamics tools for the baffle cut given to the modified heat exchanger are utilized for the calculation of

various parameters like the pressure decline, desired baffle inclination angle and mass flow rate, outlet temperature at the

shell side and recirculation at baffle side for the particular geometry of the heat exchanger. Small corners at variable angles

of the liquid flow are the result of introduction of segmental baffles which improves heat transfer and huge decline in

pressure thus increasing the fouling resistance. This recorded an effective heat transfer hike by the impact of helical baffle.

The most desirable heat transfer coefficient of the highest order and pressure decline of the lowest order are the result

generated in heat exchanger. Thus, the present study conclusively improved the performance of the heat exchanger by the use

of helical baffle in place of segmental baffle from the numerical experimentation results.

Keywords: Shell and tube heat exchanger, computational fluid dynamics tools, helix Baffles, Heat Transfer Coefficient,

Pressure Decline.

Introduction

Highest thermal performance is the key factor determining the

efficiency of any Shell and Tube Heat Exchanger. Hence, in the

design of Heat Exchanger, the foremost considerations should

be given to the cost and effectiveness so as to improve its

efficiency. The baffles of helical type instead of segmental type

when used in conjunction with changes in its geometry by

giving a full 3600 CFD model inclination, a higher decline in

pressure across the heat exchanger could be achieved using

Ansys tools. The temperature distribution and flow structure are

favorably obtained upon fine modelling the geometry

accurately. The present study is taken up with the major

objective of obtaining pressure decline at shell side and

consequent achievement of hike in heat transfer by design and

simulation of angle of helical baffles.

Lutcha and Nemcansky1 upon investigation of the flow field

patterns generated by various helix angles used in helical baffle

geometry found that the flow patterns obtained in their study are

similar to plug flow condition which is expected to decline

pressure at shell side and increase heat transfer process

significantly. Stehlik et al.2 studied the effect of optimized

segmental baffles and helical baffles in heat exchanger based on

Bell-Delaware method and demonstrated the heat transfer and

pressure decline correction factors for a heat exchanger. Oil-

Water Shell and Tube Heat Exchangers with various baffle

geometries of 5 continuous helical baffles and one segmental

baffle and test results were compared for performance with

respect to their heat transfer coefficient and pressure decline

values at shell side by Kral et.al.3. When they have made

comprehensive comparison on the most important geometric

factor of helix angle, 400 helix angle outperformed the other

angles with respect to the heat transfer per unit shell side fluid

pumping power or unit shell side fluid pressure decline. The

flow patterns in the shell side of the shell and tube heat

exchanger with continuous helical baffles were found always

rotational and helical due to the peculiar geometry of the

continuous helical baffles which resulted in a significant

increase in heat transfer coefficient per unit pressure decline in

the shell and tube heat exchanger.

The continuous helical baffles when designed well can prevent

the flow induced vibration and fouling in the shell side. Similar

results on fouling were reported by Murugesan and

Balasubramanian4. The experimental study of Shell and Tube

Heat Exchangers with the use of continuous helical baffles can

result approximately ten per cent hike in heat transfer

coefficient in comparison with that of traditional segmental

baffles for the same shell side pressure decline. Development of

non-dimensional correlations for heat transfer coefficient and

pressure decline based on the experimental data on proposed

Research Journal of Engineering Sciences___________

Vol. 3(7), 8-16, July (2014)

International Science Congress Association

continuous helical baffle shell and tube heat exchangers with

different shell configurations will be the another objective of the

present study which might be useful for industrial applications

and basic studies on this type of heat exchangers.

Material and Methods

The tube layout and arrangement with tube pitch and tube

pitches parallel and normal to flow is typically shown for

equilateral triangular arrangement in figure-1. A computational

model of Shell and Tube Heat Exchanger with ten helix angle is

shown in figure-2 after experimental test and the details of

geometry parameters of the same are given in

figure- 2, it can be seen that the simulated Shell and Tube

exchanger has total number of tubes seven and with six cycles

of baffles in the shell side direction. The inlet and out let of the

domain are connected with the corresponding tubes. The whole

computation domain is bounded by the inner side of the shell

and everything in the shell contained in the domain.

Following assumptions are made with respect to basic

characteristics of the process to simplify numerical simulation:

The shell side fluid is having constant thermal properties, The

fluid flow and heat transfer processes are in steady state and

turbulent, the leak flows between tube and

between baffles and shell are neglected, the natural convection

induced by the fluid density variation is neglected, the tube wall

temperature kept constant in the whole shell side and the heat

exchanger is well insulated so that the heat l

environment is totally neglected. The following Navier Stokes

Equation5 solved in every mess shell and the simulation shows

the result. Gaddis (2007)6 method was used to design the model

as per the Tubular Exchanger Manufacturers Association

(TEMA) standards and the tube layout is provided in

∂tT+u∂xT+v∂yT=-1

RePr�∂x�K∂xT�+∂y�K∂yT��

Figure-1

Tube layout and arrangement

_________________________________________________

Association

continuous helical baffle shell and tube heat exchangers with

different shell configurations will be the another objective of the

might be useful for industrial applications

and basic studies on this type of heat exchangers.

The tube layout and arrangement with tube pitch and tube

pitches parallel and normal to flow is typically shown for

1. A computational

model of Shell and Tube Heat Exchanger with ten helix angle is

2 after experimental test and the details of

geometry parameters of the same are given in table 1. From

2, it can be seen that the simulated Shell and Tube heat

has total number of tubes seven and with six cycles

l side direction. The inlet and out let of the

domain are connected with the corresponding tubes. The whole

computation domain is bounded by the inner side of the shell

and everything in the shell contained in the domain.

th respect to basic

characteristics of the process to simplify numerical simulation:

The shell side fluid is having constant thermal properties, The

fluid flow and heat transfer processes are in steady state and

turbulent, the leak flows between tube and baffle and that

between baffles and shell are neglected, the natural convection

induced by the fluid density variation is neglected, the tube wall

temperature kept constant in the whole shell side and the heat

exchanger is well insulated so that the heat loss to the

llowing Navier Stokes

solved in every mess shell and the simulation shows

method was used to design the model

as per the Tubular Exchanger Manufacturers Association

MA) standards and the tube layout is provided in figure- 1.

��

Tube layout and arrangement

Figure-

Computational model of Shell and tube heat exchanger with

tubes and baffle inclination

Table-1

Geometric dimensions of shell and tube heat exchanger

Length of Heat exchanger, (L)

Inner diameter of Shell (Di)

Outer diameter of Tube (do)

Tube bundle geometry and pitch (Triangular)

Number of tubes (Nt)

Number of baffles (Nb)

Central baffle spacing B

Baffle inclination angle (θ)

In order to get the correct velocity and thermal boundary layers

with much less computation, the hexahedral mesh elements

were utilized in discretizing the 3 D model in ICEM CFD. Fine

control near the wall surface on hexahedral mesh was ensured

so as to get the correct boundary layer gradient. In an effort to

get correct number of nodes, best control was obtained by

discretizing the shell and tube heat exchanger into solid and

fluid domains. For six baffles of the entire geometry divisions,

the fluid domains are distinguished as Fluid Inlet, Fluid Outlet

and Fluid Shell and the solid domains are numbered from Solid

Baffle 1 to Solid Baffle 6. Fluid mesh finer than solid mesh is

used in the simulation of conjugate heat transfer process. In

order to capture velocity and thermal boundary layers, a fluid

domain which spans 100 microns is the height of the 1

from the tube surface. A minimum angle and minimum

determinant of 180 and 4.12 respectively are found when the

discretized model is checked for qualit

quality is met when the meshes are checked for errors and then

it is exported to the pre-processor (ANSYS CFX).

Initially a relatively coarser mesh is generated with 1.8

Million cells. This mesh contains mixed cells

Hexahedral cells) having both triangular and quadrilateral

faces at the boundaries. Care is taken to use structured

cells (Hexahedral) as much as possible, for this reason the

geometry is divided into several parts

methods available in the ANSYS meshing client. It is

0.0 100.0 200.0 (mm)

50.0 150.0

_____________ ISSN 2278 – 9472

Res. J. Engineering Sci.

9

-2

Computational model of Shell and tube heat exchanger with

baffle inclination

1

Geometric dimensions of shell and tube heat exchanger

600 mm

90 mm

20 mm

Tube bundle geometry and pitch (Triangular) 30 mm

7

6

86 mm

0 to 40

In order to get the correct velocity and thermal boundary layers

with much less computation, the hexahedral mesh elements

were utilized in discretizing the 3 D model in ICEM CFD. Fine

control near the wall surface on hexahedral mesh was ensured

et the correct boundary layer gradient. In an effort to

get correct number of nodes, best control was obtained by

discretizing the shell and tube heat exchanger into solid and

fluid domains. For six baffles of the entire geometry divisions,

ns are distinguished as Fluid Inlet, Fluid Outlet

and Fluid Shell and the solid domains are numbered from Solid

Baffle 1 to Solid Baffle 6. Fluid mesh finer than solid mesh is

used in the simulation of conjugate heat transfer process. In

elocity and thermal boundary layers, a fluid

domain which spans 100 microns is the height of the 1st cell

A minimum angle and minimum

and 4.12 respectively are found when the

discretized model is checked for quality. The minimum required

quality is met when the meshes are checked for errors and then

processor (ANSYS CFX).

Initially a relatively coarser mesh is generated with 1.8

Million cells. This mesh contains mixed cells (Tetra and

Hexahedral cells) having both triangular and quadrilateral

faces at the boundaries. Care is taken to use structured

cells (Hexahedral) as much as possible, for this reason the

geometry is divided into several parts for using automatic

methods available in the ANSYS meshing client. It is

0.0 100.0 200.0 (mm)

50.0 150.0


Vol. 3(7), 8-16, July (2014)


meant to reduce numerical diffusion as much as possible

by structuring the mesh in a well manner, particularly near

the wall region. Later on, for the mesh independent model, a

fine mesh is generated with 5.65 Million cells. For this fine

mesh, the edges and regions of high temperature and pressure

gradients are finely meshed. The details are provided in

3 and 4.

Figure-3

Meshing diagram of shell and tube heat exchanger

Figure-4

Surface mesh with Helical Baffle and tube bundle of shell

and tube heat exchanger

ANSYS® FLUENT® v13 was used to carry out simulation.

Steady time and absolute velocity formation were selected for

the simulation after selecting Pressure Based type in the Fluent

solver. Option energy calculation was on in the model, and the

standard wall function was set as (k-epsilon 2 eqn.), the viscous

was set as standard k-e. In cell zone fluid water

selected. Water-liquid and copper, aluminum was selected as

materials for simulation. Boundary condition was selected for

inlet, outlet. In inlet and outlet 1Kg/s velocity and

temperature was set at 353K. Across each tube 0.05Kg/s

velocity and 300K temperature was set. Mass flow was selected

in each inlet. In reference Value Area set as 1m

Kg/m3, enthalpy 229485 J/Kg, length 1m, temperature 353K,

0.000 0.200 (m)

0.100

_________________________________________________

Association

meant to reduce numerical diffusion as much as possible

by structuring the mesh in a well manner, particularly near

the mesh independent model, a

fine mesh is generated with 5.65 Million cells. For this fine

mesh, the edges and regions of high temperature and pressure

gradients are finely meshed. The details are provided in figure-

Meshing diagram of shell and tube heat exchanger

Surface mesh with Helical Baffle and tube bundle of shell

ANSYS® FLUENT® v13 was used to carry out simulation.

Steady time and absolute velocity formation were selected for

the simulation after selecting Pressure Based type in the Fluent

solver. Option energy calculation was on in the model, and the

epsilon 2 eqn.), the viscous

e. In cell zone fluid water-liquid was

liquid and copper, aluminum was selected as

materials for simulation. Boundary condition was selected for

inlet and outlet 1Kg/s velocity and

temperature was set at 353K. Across each tube 0.05Kg/s

velocity and 300K temperature was set. Mass flow was selected

in each inlet. In reference Value Area set as 1m2, Density 998

length 1m, temperature 353K,

Velocity 1.44085 m/s, Ration of specific heat 1.4 was

considered.

SIMPLEC was set as Pressure Velocity coupling and Skewness

correction was set at zero. In Spatial Discretization zone, Least

square cell based Gradient and st

Momentum, Turbulent Kinetic Energy and Energy all were set

as First order upwind. In Solution control, Pressure was 0.7,

Density 1 , Body force 1, Momentum 0.2 , turbulent kinetic

and turbulent dissipation rate was s

turbulent Viscosity was 1. Solution initialization was standard

method and solution was initialized from inlet with 300K

temperature. Under the Above boundary condition and solution

initialize condition, simulation was set for 1000 it

convergence of solution; the continuity, X

Z-velocity, k, epsilion should be less than 10

should be less than 10-7

. The heat transfer rate is calculated

from the following formulae from which h

is calculated across shell side. Q = m * Cp *

mass flow rate, Cp = Speific Heat of Water,

difference between tube side

Results and Discussion

Baffle inclination: For Zero degree baffle inclination

solution was converged at 160th

Baffle inclination is converged at 133

200 baffle inclination is converged at 138

results were reported by Khairun et al.

Variation of Temperature: Three different plots of

temperature profile are taken in comparison with the baffle

inclination at 00, 10

0, 20

0 and temperature distribution across

tube outlet at 00 are given in figure-

Figure-

Temperature Distribution across the tube and shell

35

3.0

0

35

0.3

5

34

7.7

0

34

5.0

5

34

2.4

0

33

9.7

5

33

7.1

0

33

4.4

4

33

1.7

9

32

9.1

4

32

6.4

9

32

3.8

4

32

1.1

9

_____________ ISSN 2278 – 9472


10

Velocity 1.44085 m/s, Ration of specific heat 1.4 was

SIMPLEC was set as Pressure Velocity coupling and Skewness

correction was set at zero. In Spatial Discretization zone, Least

square cell based Gradient and standard Pressure were used.

Momentum, Turbulent Kinetic Energy and Energy all were set

as First order upwind. In Solution control, Pressure was 0.7,

Density 1 , Body force 1, Momentum 0.2 , turbulent kinetic

and turbulent dissipation rate was set at 1, energy and

turbulent Viscosity was 1. Solution initialization was standard

method and solution was initialized from inlet with 300K

temperature. Under the Above boundary condition and solution

initialize condition, simulation was set for 1000 iteration. For

convergence of solution; the continuity, X-velocity, Y velocity,

velocity, k, epsilion should be less than 10-4

and the energy

. The heat transfer rate is calculated

from the following formulae from which heat transfer rate

is calculated across shell side. Q = m * Cp * ∆T Where m =

mass flow rate, Cp = Speific Heat of Water, ∆T = Temperature

For Zero degree baffle inclination th

iteration. Simulation of 100

Baffle inclination is converged at 133th

iteration. Simulation of

baffle inclination is converged at 138th

iteration. Similar

results were reported by Khairun et al.7.

Three different plots of

temperature profile are taken in comparison with the baffle

and temperature distribution across

-5, 6, 7 and 8.

-5

Distribution across the tube and shell

32

1.1

9

31

8.5

4

31

5.8

9

31

3.2

4

31

0.5

9

30

7.9

4

30

5.2

8

30

2.6

3

29

9.9

6


Vol. 3(7), 8-16, July (2014)


Figure-6

Temperature Distribution for 100 baffle inclination

Figure-7

Temperature Distribution of 200 baffle inclination

Temperature of the hot water in shell and tube heat exchanger at

inlet was 353K and in outlet it became 347K. In case of cold

water, inlet temperature was 300K and the outlet became 313K.

Similar results were reported by Usman and Goteberg, 2011

Tube outlet Temperature Distribution was given below in

exchanger (figure-8). Similar enhanced heat transfers in heat

exchangers were reported by Murugesan and

Balasubramanian9,10

.

Variation of Velocity: The flow distribution across the cross

section at different positions in heat exchanger is understood by

the examination of Velocity profile. Velocity profile of Shell

and Tube Heat exchanger at different inclinations of Baffle are

shown in Figures 9, 10 and 11. The heat exchanger is modeled

considering the plane symmetry. The velocity profile at inlet is

same for all three inclination of baffle angle i.e 1.44086 m/s.

Outlet velocity vary tube to helical baffle and turbulence occur

in the shell region as reported earlier11

.

35

3.0

0

35

0.3

5

34

7.7

0

34

5.0

5

34

2.4

0

33

9.7

5

33

7.1

0

33

4.4

4

33

1.7

9

32

9.1

4

32

6.4

9

32

3.8

4

32

1.1

9

31

8.5

4

31

5.8

9

31

3.2

4

35

3.0

0

35

0.3

5

34

7.7

0

34

5.0

5

34

2.4

0

33

9.7

5

33

7.1

0

33

4.4

4

33

1.7

9

32

9.1

4

32

6.4

9

32

3.8

4

32

1.1

9

31

8.5

4

31

5.8

9

31

3.2

4

_________________________________________________

Association

baffle inclination

baffle inclination

Temperature of the hot water in shell and tube heat exchanger at

inlet was 353K and in outlet it became 347K. In case of cold

water, inlet temperature was 300K and the outlet became 313K.

Similar results were reported by Usman and Goteberg, 20118.

let Temperature Distribution was given below in

8). Similar enhanced heat transfers in heat

Murugesan and

The flow distribution across the cross

exchanger is understood by

the examination of Velocity profile. Velocity profile of Shell

and Tube Heat exchanger at different inclinations of Baffle are

The heat exchanger is modeled

ity profile at inlet is

same for all three inclination of baffle angle i.e 1.44086 m/s.

Outlet velocity vary tube to helical baffle and turbulence occur

Figure-

Temperature Distribution across Tube outlet in 0

inclination

Figure-

Velocity profile across the shell at 0

Figure-10

Velocity profile across the shell at 10

31

3.2

4

31

0.5

9

30

7.9

4

30

5.2

8

30

2.6

3

29

9.9

6

31

3.2

4

31

0.5

9

30

7.9

4

30

5.2

8

30

2.6

3

29

9.9

6

35

3.0

0

35

0.3

5

34

7.7

0

34

5.0

5

34

2.4

0

33

9.7

5

33

7.1

0

33

4.4

4

33

1.7

9

32

9.1

4

32

6.4

9

32

3.8

4

6

.98

6

.63

6

.26

5

.93

5

.58

5

.23

4

.88

4

.53

4

.19

3

.84

3

.49

3

.14

6

.46

6

.14

5

.81

5

.49

5

.17

4

.85

4

.52

4

.20

3

.88

3

.55

3

.23

2

.91

Counters of static temperature (K)

_____________ ISSN 2278 – 9472


11

-8

across Tube outlet in 00 baffle

inclination

-9

Velocity profile across the shell at 00 baffle inclination

10


32

1.1

9

31

8.5

4

31

5.8

9

31

3.2

4

31

0.5

9

30

7.9

4

30

5.2

8

30

2.6

3

29

9.9

6

2

.79

2

.44

2

.09

1

.74

1

.40

1

.05

0

.70

0

.35

0

.00

2

.58

2

.26

1

.94

1

.62

1

.29

0

.97

0

.65

0

.32

0

.00

Counters of static temperature (K)


Vol. 3(7), 8-16, July (2014)


Figure-11


Variation of Pressure: Figure-12, 13 and 14 shows the

pressure distribution across shell and tube heat exchanger at

different baffle inclinations. With every increase in baffle

inclination angle, the pressure decline inside the shell is

decreased and the pressure was found varying widely from inlet

to outlet.

The contours of static pressure are shown in all the figures to

give a detailed idea.

Figure-12

Pressure Distribution across the shell at 0

inclination.

Change in Outlet Temperature with respect to baffle inclination angle

Baffle Inclination Angle

(Degree)

Outlet Temperature of

0

10

20

6

.98

6

.63

6

.26

5

.93

5

.58

5

.23

4

.88

4

.53

4

.19

3

.84

3

.49

3

.14

2

.79

2

.44

2

.09

1

.74

2.1

3e5

2.0

2e5

1.9

0e5

1.7

9e5

1.6

7e5

1.5

5e5

1.4

4e5

1.3

2e5

1.2

1e5

1.0

9e5

9.7

8e4

8.6

3e4

7.4

7e4

6.3

2e4

5.1

6e4

4.0

1e4

_________________________________________________

Association

baffle inclination

12, 13 and 14 shows the

pressure distribution across shell and tube heat exchanger at

different baffle inclinations. With every increase in baffle

inclination angle, the pressure decline inside the shell is

ure was found varying widely from inlet

The contours of static pressure are shown in all the figures to

Pressure Distribution across the shell at 00 baffles

Figure-13


inclination

Figure-14


inclination

Changes in outlet temperatures are shown in Table 2 and in

Figure- 15.

Similar heat transfers are reported by Emerson

Kottek13

Table-2


Outlet Temperature of Shell side

(Kelvin)

Outlet Temperature

346

347.5

349

1

.74

1

.40

1

.05

0

.70

0

.35

0

.00

4.0

1e4

2.8

6e4

1.7

0e4

5.5

1e3

-6.0

2e3

-1.7

6e4

2.1

8e5

2.0

6e5

1.9

5e5

1.8

3e5

1.7

2e5

1.6

1e5

1.4

9e5

1.3

8e5

1.2

6e5

1.1

5e5

1.0

3e5

9.1

8e4

8.0

4e4

2.1

8e5

2.0

6e5

1.9

5e5

1.8

3e5

1.7

2e5

1.6

0e5

1.4

9e5

1.3

8e5

1.2

6e5

1.1

5e5

1.0

3e5

9.1

8e4

8.0

3e4

_____________ ISSN 2278 – 9472


12

13

Distribution across the shell at 100 baffle

inclination

14

Pressure Distribution across the shell at 200 baffle

inclination

Changes in outlet temperatures are shown in Table 2 and in

ansfers are reported by Emerson12

and Li and


Outlet Temperature of Tube side

(Kelvin)

317

319

320

8.0

4e4

6.8

9e4

5.7

5e4

4.6

0e4

3.4

6e4

2.3

1e4

1.1

7e4

2.2

6e2

-1.1

2e4

8.0

3e4

6.8

9e4

5.7

5e4

4.6

0e4

3.4

6e4

2.3

1e4

1.1

7e4

2.1

7e2

-1.1

2e4


Vol. 3(7), 8-16, July (2014)


300

310

320

330

340

350

360

0 10

Tem

per

atu

re

Baffle Inclination Angle (degree)

Figure-15

Plot of Baffle inclination angle vs Outlet Temperature of

shell and tube side

It has been found that the increasing baffle inclination angle

from 00 to 20

0 affect the outlet temperature of shell side

significantly. Pressure Decline inside Shell with respect to

baffle inclination angle is provided in table 3.

Similar results were reported by Diaper and Hesler, 1990

Sunil and Pancha15

and Zhang et al., 2008

Computational Fluid Dynamics software. Pressure Decline

inside Shell with respect to baffle inclination angle is provided

in figure-16. Velocity inside the shell with respect to baffle

inclination angle from 00 to 20

0 is detailed in

17.

Plot of Baffle angle vs Pressure Decline

227.5

228

228.5

229

229.5

230

230.5

231

231.5

0

Pre

ssure

dec

line

(kP

a)

_________________________________________________

Association

20


Shell

Outlet …

Plot of Baffle inclination angle vs Outlet Temperature of

It has been found that the increasing baffle inclination angle

affect the outlet temperature of shell side

significantly. Pressure Decline inside Shell with respect to

Similar results were reported by Diaper and Hesler, 199014

,

and Zhang et al., 200816

using

Computational Fluid Dynamics software. Pressure Decline

inside Shell with respect to baffle inclination angle is provided

16. Velocity inside the shell with respect to baffle

is detailed in table 4 and figure-

The shell-side pressure declines when the baffle inclination

angle is increased from 00 to 20

exchanger a 100

baffle inclination angle results in pressure drop

of 4 per cent and 200

baffle inclination angle results in

drop of 16 per cent when compared to the pressure drop at 0

baffle inclination angle as shown in

generalized that with increase in baffle inclination, pressure

decline decreases, so that it affect in heat transfer rate, which

increased.

Table-3

Pressure Decline inside Shell with respect to baffle

inclination angle


(Degree)

0

10

20

Table-4

Velocity inside Shell with respect to baffle


(Degree)

0

10

20

Similar performance resulting from baffle inclinations in heat

exchangers are reported by Thirumarimurugan et al., 2008

Figure-16

Plot of Baffle angle vs Pressure Decline

10

Baffle angle

_____________ ISSN 2278 – 9472


13

side pressure declines when the baffle inclination

to 200. For shell and tube heat

baffle inclination angle results in pressure drop

baffle inclination angle results in pressure

drop of 16 per cent when compared to the pressure drop at 00

baffle inclination angle as shown in figure-16. So, it is

generalized that with increase in baffle inclination, pressure

decline decreases, so that it affect in heat transfer rate, which is

3

Pressure Decline inside Shell with respect to baffle

inclination angle

Pressure Decline Inside

Shell (kPA)

230.992

229.015

228.943

4

Velocity inside Shell with respect to baffle inclination angle

Velocity inside shell

(m/sec)

4.2

5.8

6.2

Similar performance resulting from baffle inclinations in heat

exchangers are reported by Thirumarimurugan et al., 200817

.

20

Pressure …

Research Journal of Engineering Sciences________________________________________________________ ISSN 2278 – 9472



The outlet velocity is increasing with increase in baffle

inclination so that more will be heat transfer rate with increasing

velocity.

Heat Transfer Rate: The Plot showing that with increasing

baffle inclination, heat transfer rate increase. For better heat

transfer rate, helical baffle is used and results is shown in figure-

18 and table 5. The overall values obtained in simulation are

given in table 6.

Table-5

Heat Transfer Rate across Tube side with respect to baffle

inclination angle


(Degree)

Heat Transfer Rate Across

Tube side (W/m2)

0 3557.7

10 3972.9

20 4182

Figure-17

Plot of Velocity profile inside shell

Figure-18

Heat Transfer Rate along Tube side

0

1

2

3

4

5

6

7

0 10 20

Vel

oci

ty (

m/s

)


Velocity Plot Across Shell side

Velocity …

3200

3300

3400

3500

3600

3700

3800

3900

4000

4100

4200

4300

0 10 20

Hea

t T

ransf

er r

ate

(W/m

2)


Heat Transfer rate




Table-6

Overall Calculated value in Shell and Tube heat exchanger in simulation

Baffle inclination

(in Degree)

Shell Outlet

Temperature

(Kelvin)

Tube Outlet

Temperature

(Kelvin)

Pressure

Drop

Heat Transfer

Rate(Q) (in W/m2)

Outlet

Velocity(m/s)

00 346 317 230.992 3554.7 4.2

100 347.5 319 229.015 3972.9 5.8

200 349 320 228.943 4182 6.2

Conclusion

The following are the salient points emerged from this study.

The simulation was converged at 160

th iteration for zero degree

baffle inclination. Simulation of ten degree baffle inclination

was converged at 133rd

iteration. Simulation of twenty degree

baffle inclination was converged at 138th iteration. Temperature

of the cold water in shell and tube heat exchanger at the inlet

was 300K and at the outlet was 313K. In case of hot water, inlet

temperature was 353K and at the outlet became 347K. The

velocity profile at outlet vary tube to helical baffle and

turbulence occur in the shell region. The velocity profile at inlet

was same for all the three inclination of baffle angle i.e 1.44086

m/s. The pressure decline inside the shell is decreased with the

increase in baffle inclination angle. The pressure vary widely

from inlet to outlet.

Outlet temperature of shell side was much affected while the

baffle inclination angle was increased from 00 to 20

0. This was

because of decrease in shell side pressure decline. The pressure

decline was found to decrease by 4 per cent with 100 and 16 per

cent with 200 baffle inclination. The outlet velocity also

increases with increase in baffle inclination and cause a further

increase in heat transfer.

The prediction of pressure decline and heat transfer of the model

was found to be with an average error of 20 per cent. Rapid

mixing and change in flow direction was observed in inlet and

outlet region and found to be the only exception for the

assumption in geometry and meshing. Reliable results was

observed with the model by considering the standard k-e and

wall function. It could also be seen that the mass flow rate when

increased beyond 2kg/s; the pressure decline suddenly increases

with practically nil variation in outlet temperature for the given

geometry. The unsupported behavior of center row of tubes

makes the baffle use ineffective when the baffle angle is above

200. Hence, the helix baffle inclination angle of 20

0 makes the

best performance of shell and tube heat exchanger.

References

1. Lutcha J. and Nemcansky J., Performance improvement of

tubular heat exchangers by helical baffles, Chemical

Engineering Research and Design, 68, 263-270 (1990)

2. Stehlík P., Nemcansky J., Kral D. and Swanson L.W.,

Comparison of correction factors for shell-and-tube heat

exchangers with segmental or helical baffles, Heat

Transfer Engineering, 15(1), 55-65 (1994)

3. Kral D., Stehlik P., Ploeg V.D.H.J. and Master B.I.,

Helical baffles shell-and tube heat exchangers, 1:

Experimental verification, Heat Transfer Engg., 17(1), 93–

101 (1996)

4. Murugesan M.P. and Balasubramanian R., To Study the

Fouling of Corrugated Plate Type Heat Exchanger in the

Dairy Industry, Res. J. Engineering Sci., 2(1), 5-10 (2013)

5. Temam R. (Ed.), Claude-Louis Navier and Gabriel Stokes

Navier-Stokes Equations: Theory and Numerical Analysis,

Institut for Scientific Computing and Applied

Mathematics, Indiana University, USA (1977)

6. Gaddis D. Standards of the Tubular Exchanger

Manufacturers Association, TEMA Inc, 9th

ed., Tarrytown,

USA (2007)

7. Khairun H.O., CFD simulation of heat transfer in shell and

tube heat exchanger, Bachelor in chemical Engineering

(Gas Technology) Thesis (2009)

8. Usman U.E. and Goteborg, Heat Transfer Optimization

of Shell-and-Tube & Heat Exchanger through

CFD, Master’s Thesis, Chalmers University of

Technology, Sweden (2011)

9. Murugesan M.P. and Balasubramanian R., The Effect

of Mass Flow Rate on the Enhanced Heat Transfer

Characteristics in A Corrugated Plate Type Heat

Exchanger, Res. J. Engineering Sci., 1(6), 22-26 (2012)

10. Murugesan M.P. and Balasubramanian R., The

Experimental Study on Enhanced heat Transfer

Performance in Plate Type Heat Exchanger, Res. J.

Engineering Sci., 2(2), 16-22 (2013)

11. Haseler L.E., Wadeker V.V. and Clarke R.H., Flow

Distribution Effect in a Plate and Frame Heat Exchanger, I

Chem E Symposium Series, 129, 361-367 (1992)

12. Emerson W.H. Shell-side pressure drop and heat

transfer with turbulent flow in segmentally baffled

shell-tube heat exchangers, Int. J. Heat Mass Transfer,

6, 649–66 (1963)

13. Li H. and Kottek V., Effect of baffle spacing on

pressure drop and local heat transfer in shell and tube

heat exchangers for staggered tube arrangement, Int. J.

Heat Mass Transfer, 41(10), 1303–1311 (1998)




14. Diaper A.D. and Hesler L.E., Cross flow Pressure Drop

and Flow Distributions within a Tube Bundle Using

Computational Fluid Dynamic, Proc. Heat Transfer Conf.,

Israel, 235-240 (1990)

15. Sunil K.S. and Pancha M.H., Comparative thermal

performance of shell and tube heat Exchanger with

continuous helical baffle using different angles,

International Journal of Engineering Research and

Applications, 2(4), 2264-2271 (2012)

16. Zhang J.F., He Y.L. and Tao W.Q., 3 D numerical

simulation of shell and tube heat exchanger with middle-

overlapped helical baffle, Journal of School of energy and

power engineering, 132, 1-8 (2008)

17. Thirumarimurugan M., Kannadasan T. and Ramasamy E.,

Performance Analysis of Shell and Tube Heat

Exchanger Using Miscible System, American Journal of

Applied Sciences, 5, 548-552 (2008)

design of shell and tube heat exchanger using ... · pdf filedesign of shell and tube heat...

Documents