ISSN (Online) : 2319 - 8753

ISSN (Print) : 2347 - 6710

International Journal of Innovative Research in Science, Engineering and Technology

An ISO 3297: 2007 Certified Organization Vol.4, Special Issue 12, September 2015

2 nd
International Conference on Emerging Trends in Mechanical Engineering (ICETME–2015)
On 3rd, 4th & 5th September 2015
Organized by
Department of Mechanical Engineering, Toc H Institute of Science & Technology, Ernakulam-682313, India

Optimization of Shell & Tube Heat Exchanger

by Baffle Inclination & Baffle Cut
Joemer.C.S 1, Sijo Thomas 2, Rakesh.D 3, Nidheesh.P 4
B.Tech Student, Dept. of Mechanical Engineering, Toc H Institute of Science and Technology, Ernakulam, Kerala,
India 1, 2, 3
Assistant Professor, Dept. of Mechanical Engineering, Toc H Institute of Science and Technology, Ernakulam, Kerala,
India 4

ABSTRACT: Heat exchanger is an equipment for heat transfer from one medium to other. This paper deals with
optimizations of shell and tube heat exchanger for maximum heat transfer, by the optimization of baffle cut & baffle
angle of a particular shell and tube heat exchanger using CFD analysis. The performance of the shell and tube heat
exchanger was studied by varying the parameters using CFD software package fluent. To validate the CFD algorithm
the experiment was conducted on an existing single pass counter flow shell and tube heat exchanger. The optimum
values obtained are baffle angle 5°, baffle cut 25%.

KEYWORDS: Shell and tube heat exchanger; Optimizations, CFD

I. INTRODUCTION
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. This device used to transfer heat between two or more fluids that are
at different temperatures and which in most of the cases they are separated by a solid wall. Heat exchangers are used in
power plants, nuclear reactors, refrigeration and air conditioning systems, automotive industries, heat recovery systems,
chemical processing, and food industries. Different heat exchangers are named according to their applications. For
example, heat exchangers being used to condense are known as condensers, similarly heat exchangers for boiling
purposes are called boilers [1]. Shell and tube heat exchangers (STHXs) have been most widely used equipment in the
industrial fields including: power plant, petroleum refining, steam generation etc. STHXs provide relatively large ratios
of heat transfer area to volume and weight and can be easily cleaned [2].Performance and efficiency of heat exchangers
are measured through the amount of heat transferred using least area of heat transfer and pressure drop. Baffle Angle,
Baffle Cut, Baffle Spacing, Tube Diameter and Number of Tubes These are the main factors affecting heat transfer of
Heat exchanger. The optimization of shell-and-tube heat exchangers requires a good knowledge of the local and
average shell-side heat transfer coefficients which is complicated by a shell diameter, baffle cut, baffle spacing, tube
diameter, pitch, arrangement. These leakages reduce the velocity in the tube bundle and, hence, the heat transfer
coefficient and pressure drop [3].

II. CFD ANALYSIS

The fluid flow through the shell and heat transfer can be analysed using by CFD analysis. CFD (Computational Fluid
Dynamics) it is a branch of that uses numerical methods and algorithms to solve and analyse problems that involve
fluid flows. Computers are used to perform the calculations required to simulate the interaction of liquids and gases
with surfaces defined by boundary conditions.CFD tools are used to predict the performance at various conditions. The
flow characteristics such as pressure, volumetric flow, velocity and temperature at each point can be obtained from
CFD tools. ANSYS FLUENT software is a high-performance, general purpose fluid dynamics program that has been
applied to solve wide-ranging fluid flow problems. At the heart of ANSYS FLUENT is its advanced solver technology,
the key to achieving reliable and accurate solutions quickly and robustly.

Copyright to IJIRSET www.ijirset.com 69

 ISSN (Online) : 2319 - 8753
ISSN (Print) : 2347 - 6710

International Journal of Innovative Research in Science, Engineering and Technology

An ISO 3297: 2007 Certified Organization Vol.4, Special Issue 12, September 2015

2 nd
International Conference on Emerging Trends in Mechanical Engineering (ICETME–2015)
On 3rd, 4th & 5th September 2015
Organized by
Department of Mechanical Engineering, Toc H Institute of Science & Technology, Ernakulam-682313, India

(a) (b)
Boundary name Type
Shell inlet Velocity inlet
Shell outlet Pressure outlet
Tube inlet Velocity inlet
Tube outlet Pressure outlet
Shell wall tube wall Wall
Domain inside shell Fluid
Domain inside tube Fluid
Domain of baffles Solid

(c) (d)
Fig 1(a) shows the shell and tube heat exchanger before meshing, 1(b) shows the shell and tube heat exchanger after
meshing, 1(c) shows the shell and tube heat exchanger boundaries and flow directions, 1(d) shows the boundary types
and the continuum types given in the boundary conditions.

III. GOVERNING EQUATIONS

The Navier-Stokes equations are the basic governing equations for a fluid flow. It is obtained by applying Newton's
second Law of Motion to a fluid element and is also called the momentum equation. It is supplemented by the mass
conservation equation, also called continuity equation and the energy equation.

(i) Continuity Equation

In fluid dynamics, the continuity equation is an expression of conservation of mass. For a steady or unsteady
incompressible 3 dimensional flow, the continuity equation can be expressed in Cartesian co-ordinates as:

u v w
  0 (1)
x y z

Where u, v and w are the components of velocity field in x, y and z directions respectively.

Copyright to IJIRSET www.ijirset.com 70

 ISSN (Online) : 2319 - 8753
ISSN (Print) : 2347 - 6710

International Journal of Innovative Research in Science, Engineering and Technology

An ISO 3297: 2007 Certified Organization Vol.4, Special Issue 12, September 2015

2 nd
International Conference on Emerging Trends in Mechanical Engineering (ICETME–2015)
On 3rd, 4th & 5th September 2015
Organized by
Department of Mechanical Engineering, Toc H Institute of Science & Technology, Ernakulam-682313, India
(ii) Momentum Equation (Navier-Stokes Equation)

The Navier-Stokes equations are the basic governing equations for a fluid flow. It is obtained by applying Newton's
Second Law of Motion to a fluid element and is also called the momentum equation. The Navier Stokes equation in
scalar form for x, y and z directions are as follows.

a) Along x-direction
 u u u u  p   2u  2u  2u 
 t             2  2  2
z 
u v w g
x y x  x y z 
x
 (2)
b) Along y-direction
 v v v v  p   2v  2v  2v 
 t             x 2  y 2  z 2 
z 
u v w g (3)
x y y
y
  
c) Along z-direction
 w w w w  p  2w 2w 2w 
 t  u x  v y  w z      z  g z    x 2  y 2  z 2  (4)
   
Where p represents pressure, ρ is the density, µ is the dynamic viscosity and g is the acceleration due to gravity.

(iii) Energy Equation

 T T T T    2T  2T  2T 
 Cp    u v  w   k 2  2  2   s (5)
 t x y z   x y z 
Where ‘S’ represent dissipation rate and ‘k’ is the thermal conductivity.

IV. CODE VALIDATION IN CFD & NUMERICAL METHODOLOGY

The experimental results were tabulated and the net heat transfer is calculated. And this result is later used for
validating the algorithm used in CFD analysis. The algorithm used in this endeavour SIMPLE. It was validated by
running the case with SST k-ω. k-ω gives better results when the flow is near to the wall. But when the flow reaches
near to the bulk the value of the k-ω code has greater error. So SST model is used. SST model is a combination of k-ω
and k-ε. k-ε code gives a better value in the bulk of the flow. So SST model is opted and then the value of the CFD
results begins to be comparable to the results obtained from the experiments [4].

Inlet Conditions
Cold inlet : Velocity inlet = .708 m/s Software package FLUENT 6.3.26
Cold inlet :Temperature = 303 K Solver algorithm SIMPLE (Semi Implicit Method
Hot inlet : Velocity outlet = 0.298 m/s for Pressure Linked Equation )
Turbulence model K-omega SST
Hot inlet :Temperature = 338 K Grid sizes used for the grid 1 mm
Outlet Conditions: independent study 2 mm
Hot outlet : Pressure outlet = P atm 3 mm
Cold outlet : Pressure outlet = P atm 4 mm
optimum grid size 3.0mm

(a) (b)
(b) (b)
Fig 2(a) Shows the conditions given in the fluent for obtaining results. 2(b) shows the numerical methodology.

Copyright to IJIRSET www.ijirset.com 71

 ISSN (Online) : 2319 - 8753
ISSN (Print) : 2347 - 6710

International Journal of Innovative Research in Science, Engineering and Technology

An ISO 3297: 2007 Certified Organization Vol.4, Special Issue 12, September 2015

2 nd
International Conference on Emerging Trends in Mechanical Engineering (ICETME–2015)
On 3rd, 4th & 5th September 2015
Organized by
Department of Mechanical Engineering, Toc H Institute of Science & Technology, Ernakulam-682313, India
V. CFD RESULTS AND DISCUSSION
In CFD after code validation each parameters are changed and the net heat transfer for each specific design is
calculated and is tabulated. From this result optimum value for each design changes is obtained and later this value is
fixed and the next parameter is changed. At last an optimum design is calculated.

i) BAFFLE ANGLE

The initial baffle angle is 0° and later this is varied to 5°, 10°, 15°, and 20°. The maximum total heat transfer is
5047.68W and it is obtained for 5° baffle angle which is taken as optimum baffle angle.

Sl.no Baffle Total heat surface heat Turbulent

Angle transfer rate(W) transfer coefficient intensity
(degree) (w/m2k) (%)

1 0 4147.83 516.06 24.14%

2 5 5047.68 522.76 39.85%
3 10 3917.05 418.27 36.37%
4 15 4139.91 501.79 26.04%
5 20 3625.36 450.13 10.77%

(a) (b)
Fig 3(a) The turbulent intensity contour of the shell generated in fluent for 5° baffle angle, 3(b) The surface heat
transfer coefficient contour of the tubes generated in the fluent for 5° baffle angle.

ii) BAFFLE CUT

The initial baffle cut is 20% and later this is varied to 20%, 25% and 30%. The maximum heat transfer is 5047.68W
and it is obtained for 25% baffle cut and it is taken as optimum baffle cut.

Sl.no Baffle Total heat surface heat transfer Turbulent

Cut transfer rate(W) coefficient (w/m2k) intensity
(%) (%)
1 20 3952.38 508.05 17.28%
2 25 5047.68 522.76 39.85%
3 30 4214.23 479.17 26.38%

Copyright to IJIRSET www.ijirset.com 72

 ISSN (Online) : 2319 - 8753
ISSN (Print) : 2347 - 6710

International Journal of Innovative Research in Science, Engineering and Technology

An ISO 3297: 2007 Certified Organization Vol.4, Special Issue 12, September 2015

2 nd
International Conference on Emerging Trends in Mechanical Engineering (ICETME–2015)
On 3rd, 4th & 5th September 2015
Organized by
Department of Mechanical Engineering, Toc H Institute of Science & Technology, Ernakulam-682313, India

(a) (b)
Fig 4(a) The turbulent intensity contour of the shell generated in fluent for 25% baffle angle, 4(b) The surface heat
transfer coefficient contour of the tubes generated in the fluent for 25% baffle angle.

VI. CONCLUSION
Studied and analysed the fluid flow in a shell and tube heat exchanger and it is found to be complex, three dimensional
(3D) and turbulent. The modelling and analysis was done in GAMBIT and FLUENT respectively. Optimization of
shell and tube heat exchanger model for maximum heat exchanger has done using CFD analysis. After the optimization
procedure, got 5°baffle angle and 25% Baffle cut be the optimized parameter. For both parameters, there is relation
between heat transfer and turbulent intensity. Optimized model have maximum turbulent intensity than other
arrangements.

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In Case Of Vertical Baffle, Mechanica Confab, 16-19. 2013
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