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
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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
Research Journal of Engineering Sciences___________
Vol. 3(7), 8-16, July (2014)
International Science Congress Association
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
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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
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Res. J. Engineering Sci.
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
Research Journal of Engineering Sciences___________
Vol. 3(7), 8-16, July (2014)
International Science Congress Association
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
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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)
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Res. J. Engineering Sci.
11
-8
across Tube outlet in 00 baffle
inclination
-9
Velocity profile across the shell at 00 baffle inclination
10
Velocity profile across the shell at 100 baffle inclination
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)
Research Journal of Engineering Sciences___________
Vol. 3(7), 8-16, July (2014)
International Science Congress Association
Figure-11
Velocity profile across the shell at 200 baffle inclination
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
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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
Pressure Distribution across the shell at 10
inclination
Figure-14
Pressure Distribution across the shell at 20
inclination
Changes in outlet temperatures are shown in Table 2 and in
Figure- 15.
Similar heat transfers are reported by Emerson
Kottek13
Table-2
Change in Outlet Temperature with respect to baffle inclination angle
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
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Res. J. Engineering Sci.
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
Change in Outlet Temperature with respect to baffle inclination angle
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
Research Journal of Engineering Sciences___________
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International Science Congress Association
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)
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Association
20
Baffle Inclination Angle (degree)
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
Baffle Inclination Angle
(Degree)
0
10
20
Table-4
Velocity inside Shell with respect to baffle
Baffle Inclination Angle
(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
Res. J. Engineering Sci.
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
Vol. 3(7), 8-16, July (2014) Res. J. Engineering Sci.
International Science Congress Association 14
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
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
)
Baffle Inclination Angle (degree)
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)
Baffle Inclination Angle
Heat Transfer rate
Research Journal of Engineering Sciences________________________________________________________ ISSN 2278 – 9472
Vol. 3(7), 8-16, July (2014) Res. J. Engineering Sci.
International Science Congress Association 15
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.
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