study of heat transfer in plate heat exchanger by
TRANSCRIPT
STUDY OF HEAT TRANSFER IN PLATE HEAT EXCHANGER BY USING CFD
SIMULATION
WAN NURMAISARAH BT WAN HAMARUDDIN
Thesis submitted in fulfillment of the requirements
for the award of the degree of
Bachelor of Chemical Engineering (Gas Technology)
Faculty of Chemical and Natural Resources Engineering
UNIVERSITI MALAYSIA PAHANG
JANUARY 2012
v
ABSTRACT
A plate heat exchanger is a type of heat exchanger which uses metal plates to transfer heat
between two fluids. The metal plates that commonly used are stainless steel because of its
ability to withstand high temperatures, its strength and its corrosion resistance. The basic
working principle is very simple though; the channels that formed between the plates and
corner ports are arranged so that the two fluid flows through alternate channels. The heat is
transferred through the thin plate between the channels, and creating complete counter
current flow for highest possible efficiency. No intermixing of the fluid or leakage to the
surroundings will occur as gaskets around the edges of the plates seal the unit. The
objectives of this study are to study the heat transfer performance of plate heat exchanger
for heating diesel with hot water and to observe which configurations and parameters that
gives the best results. In addition, the objective is to study and modeling the heat transfer of
plate heat exchanger using simulation. Computational Fluid Dynamic (CFD) is a tool used
in this simulation which consists of GAMBIT and FLUENT. Volume meshing in GAMBIT
is an important part to be considered before doing simulation in FLUENT as a solver.
Parameters that had been used were velocity and temperature of water. The velocity for
both diesel and hot water were calculated using mass flow rate of 100L/min, 150 L/min and
200 L/min as a basic. The temperature of hot water varies from 60°C, 70°C and 80°C.
Thus, this paper presents the simulation of heat transfer in plate heat exchanger model for
parallel and series configurations. It is observed that lower velocity and high temperature of
water gives better heat transfer performance. Parallel configuration is selected for the best
configuration in this study.
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ABSTRAK
Penukar Haba Plat (Plate Heat Exchanger) adalah sejenis penukar haba yang menggunakan
plat logam untuk pemindahan haba antara dua cecair. Plat logam yang biasa digunakan
adalah keluli tahan karat (stainless steel) kerana keupayaannya untuk menahan suhu yang
tinggi, kekuatan dan ketahanan kakisan. Prinsip kerja asas adalah sangat mudah, laluan
yang membentuk antara plat dan kedudukan sudut disusun supaya kedua-dua aliran
bendalir melalui laluan yang ditetapkan. Haba dipindahkan melalui plat nipis antara
saluran, dan mewujudkan aliran bertentangan yang lengkap bagi mencapai kebarangkalian
kecekapan tertinggi. Tiada percampuran (intermixing) cecair atau kebocoran kepada
persekitaran akan berlaku kerana gasket di sekitar pinggir plat digunakan untuk meterai
unit. Objektif kajian ini adalah untuk mengkaji prestasi pemindahan haba penukar haba plat
untuk pemanasan diesel dengan air panas dan untuk mengenalpasti konfigurasi dan
parameter yang manakah memberikan hasil yang terbaik. Di samping itu, objektif kajian
adalah untuk mempelajari dan melakar pemindahan haba untuk penukar haba plat
menggunakan simulasi. Dinamik Bendalir Komputeran (CFD) adalah alat yang digunakan
dalam simulasi ini yang terdiri daripada GAMBIT dan FLUENT. Jumlah dagangan bersirat
(volume meshing) dalam GAMBIT adalah satu bahagian penting yang perlu
dipertimbangkan sebelum melakukan simulasi dalam FLUENT sebagai penyelesai.
Parameter yang telah digunakan ialah halaju dan suhu air. Halaju bagi kedua-dua diesel dan
air panas telah dikira menggunakan kadar aliran jisim (mass flow rate) 100L/min, 150 L /
min dan 200 L / min sebagai asas. Suhu air panas berbeza dari 60 ° C, 70 ° C dan 80 ° C.
Oleh itu, kertas kerja ini membentangkan simulasi pemindahan haba dalam plat model
penukar haba untuk konfigurasi selari dan siri. Adalah diperhatikan bahawa halaju yang
lebih rendah dan suhu air yang tinggi memberikan prestasi haba pemindahan yang lebih
baik. Konfigurasi selari dipilih sebagai konfigurasi terbaik dalam kajian ini.
vii
TABLE OF CONTENTS
Page
SUPERVISOR’S DECLARATION ii
STUDENTS’S DECLARATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xii
LIST OF APPENDICES xv
CHAPTER 1 INTRODUCTION
1.1 Background of Study
1.1.1 Plate Heat Exchanger
1.1.2 History of Plate Heat Exchanger
1.1.3 Heat Transfer
1
1
2
2
1.2 Problem Statement 3
1.3 Objectives 4
1.4 Scope of Study 4
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 5
2.2 Plate Heat Exchanger 6
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2.2.1 Performances of Plate Heat exchanger
2.2.2 Advantages and Disadvantages
2.2.3 Numerical Analysis for Co-Current
2.2.4 Experimental and Numerical Heat Transfer
2.2.5 Modeling with Generalized Configurations
2.2.6 Effectiveness Charts for Counter Flow Corrugated
2.2.7 Heat Transfer Fouling and Fluid Flow
2.2.8 Effect of Flow Arrangement on the Pressure Drop
2.2.9 Flow Patterns in the Entrance
2.2.10 Flow in an Oil/Water for the Automotive Industry
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7
8
8
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12
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14
15
2.3 Diesel 16
2.4 Computational Fluid Dynamic (CFD)
2.4.1 Definition
2.4.2 History
2.4.3 Application
2.4.4 GAMBIT and FLUENT
16
17
17
18
18
CHAPTER 3 METHODOLOGY
3.1 Introduction 20
3.2 Heat Transfer Calculation
3.2.1 Thermal Properties
3.2.2 Characteristics of the Plates
3.3.3 Parameter Considerations
20
21
21
22
3.3 Computational Tools
3.3.1 CFD Modeling Overview
24
24
3.4 CFD Simulation Procedure
3.4.1 Geometry in GAMBIT
3.4.2 Physics Creation in GAMBIT
3.4.3 Mesh Generation in GAMBIT
25
25
26
28
ix
3.4.4 Simulation by FLUENT
3.4.5 Post Processing
29
32
CHAPTER 4 RESULTS AND DISCUSSION
4.1 Data Collection 33
4.2 Parallel Configuration
4.2.1 Comparison in Velocity at Temperature 60°C
4.2.2 Comparison in Temperature at Constant Velocity
35
35
42
4.3 Series Configuration
4.3.1 Comparison in Velocity at Temperature 60°C
4.3.2 Comparison in Temperature at Constant Velocity
49
50
56
4.4 Parallel versus Series 63
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 66
5.2 Recommendations
5.2.1 Parameter Calculation
5.2.2 Mesh Generation in GAMBIT
5.2.3 Numerical Diffusion
5.2.4 Unsteady State Solver
67
67
67
67
68
5.2.5 Validation of Results 68
REFERENCES 69
APPENDICES
A Plate Heat Exchanger Photo 72
B Simulated Results 73
x
LIST OF TABLES
Table No. Title Page
3.1 Thermal Properties for Materials 21
3.2 Characteristics of the plates for this study 22
3.3 Calculation of parameter 22
3.4 Volume selection 27
3.5 Faces selection 27
3.6 Boundary condition setting in FLUENT 31
4.1 Parameter 33
4.2 Area Weighted Average Static Temperature for Set 1 37
4.3 Standard Deviation Static Temperature for Set 1 37
4.4 Area Weighted Average Static Temperature for Set 2 39
4.5 Standard Deviation Static Temperature for Set 2 39
4.6 Area Weighted Average Static Temperature for Set 3 41
4.7 Standard Deviation Static Temperature for Set 3 41
4.8 Area Weighted Average Static Temperature for set 1 at 60°C 44
4.9 Standard Deviation Static Temperature for set 1 at 60°C 44
4.10 Area Weighted Average Static Temperature for set 1 at 70°C 46
4.11 Standard Deviation Static Temperature for set 1 at 70°C 46
4.12 Area Weighted Average Static Temperature for set 1 at 80°C 48
4.13 Standard Deviation Static Temperature for set 1 at 80°C 48
4.14 Area Weighted Average Static Temperature for Set 1 51
4.15 Standard Deviation Static Temperature for Set 1 51
4.16 Area Weighted Average Static Temperature for Set 2 53
4.17 Standard Deviation Static Temperature for Set 2 53
4.18 Area Weighted Average Static Temperature for Set 3 55
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4.19 Standard Deviation Static Temperature for Set 3 55
4.20 Area Weighted Average Static Temperature for set 1 at 60°C 58
4.21 Standard Deviation Static Temperature for set 1 at 60°C 58
4.22 Area Weighted Average Static Temperature for set 1 at 70°C 60
4.23 Standard Deviation Static Temperature for set 1 at 70°C 60
4.24 Area Weighted Average Static Temperature for set 1 at 80°C 62
4.25 Standard Deviation Static Temperature for set 1 at 80°C 62
4.26 Area Weighted Average Static Temperature for set 1 at 80°C- parallel
and series
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xii
LIST OF FIGURES
Figure No. Title Page
2.1 Flow Principle of Plate Heat Exchanger 6
2.2 (a) The plate pack of the PHE used in this study, (b) The CFD
representation of the fluid domain for series flow arrangement showing
a mesh detail
9
2.3 Expanded CFD representation and opened plate pack for (a) parallel
arrangement and (b) series arrangement
9
2.4 Midplane temperature distribution for the channels of a series flow
arrangement: 3D and 1D model results
10
2.5 Midplane velocity distribution for the channels of a series flow
arrangement: 3D and 1D model results
10
2.6 Temperature contours of 0.005 kg/s hot flow rate for various cold flow
rates
12
2.7 Flow and temperature distribution for distributor design C, G and H 13
2.8 Finest mesh implement using GAMBIT 15
2.9 Detail of computational mesh 16
3.1 Geometry of one plate 21
3.2 Arrangements of counter-current flows which is parallel and series 23
3.3 CFD Modeling Overview 24
3.4 GAMBIT Startup Window 25
3.5 Views of new geometry from XZ, XY, YZ plane and isometric 26
3.6 Entity zones of (a) parallel and (b) series configurations 27
3.7 Generating mesh for plate heat exchanger 28
3.8 Close view of plate heat exchanger meshing 29
3.9 k--ε turbulence model with standard wall functions 30
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3.10 Selection of materials in FLUENT 31
4.1 Location of x, y and z axis 34
4.2 Position for plotting heat transfer graph 34
4.3 Parallel configuration 35
4.4 Set 1 (a) hot flow part and (b) cold flow part 36
4.5 Graph of static temperature versus z-axis length at cold channel and
hot channel
37
4.6 Set 2 (a) hot flow part and (b) cold flow part 38
4.7 Graph of static temperature versus z-axis length at cold channel and
hot channel
39
4.8 Set 3 (a) hot flow part and (b) cold flow part 40
4.9 Graph of static temperature versus z-axis length at cold channel and
hot channel
41
4.10 60°C (a) hot flow part and (b) cold flow part 43
4.11 Graph of static temperature versus z-axis length at cold channel and
hot channel
44
4.12 70°C (a) hot flow part and (b) cold flow part 45
4.13 Graph of static temperature versus z-axis length at cold channel and
hot channel
46
4.14 80°C (a) hot flow part and (b) cold flow part 47
4.15 Graph of static temperature versus z-axis length at cold channel and
hot channel
48
4.16 Series configuration 49
4.17 Set 1 (a) hot flow part and (b) cold flow part 50
4.18 Graph of static temperature versus z-axis length at cold channel and
hot channel
52
4.19 Set 2 (a) hot flow part and (b) cold flow part 52
4.20 Graph of static temperature versus z-axis length at cold channel and
hot channel
54
4.21 Set 3 (a) hot flow part and (b) cold flow part 54
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4.22 Graph of static temperature versus z-axis length at cold channel and
hot channel
56
4.23 60°C (a) hot flow part and (b) cold flow part 57
4.24 Graph of static temperature versus z-axis length at cold channel and
hot channel
59
4.25 70°C (a) hot flow part and (b) cold flow part 59
4.26 Graph of static temperature versus z-axis length at cold channel and
hot channel
61
4.27 80°C (a) hot flow part and (b) cold flow part 61
4.28 Graph of static temperature versus z-axis length at cold channel and
hot channel
63
4.29 Graph of parallel versus series configurations for set 1 at 80°C –
parallel and series
64
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LIST OF APPENDICES
Figure Title Page
A1 Plate Heat Exchanger at FKKSA Laboratory 72
A2 Close look of plates 72
B1 Grid of sx and sy surfaces 73
B2 FLUENT calculation of outlet temperature 73
B3 FLUENT calculation of energy (unable to calculate) 74
B4 Contours of velocity 74
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CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
A heat exchanger is a device which used to transfer thermal energy (enthalpy)
between two or more fluids, between a solid surface and a fluid, or between solid
particulates and a fluid, at different temperatures and in thermal contact. Plate heat
exchanger is one of the most common heat exchanger used in industries such as oil and
gas processing system because of its compactness, easy maintenance and good heat
transfer characteristics. As its name implies, this type of heat exchanger consists of a
series of thin, corrugated plates which are pressed together in a rigid frame to form an
arrangement of flow channels with alternating hot and cold fluids.
1.1.1 Plate Heat Exchanger
A plate heat exchanger is a type of heat exchanger which uses metal plates to
transfer heat between two fluids. The metal plates that commonly used are stainless
steel because of its ability to withstand high temperatures, its strength and its corrosion
resistance. The basic working principle is very simple though; the channels that formed
between the plates and corner ports are arranged so that the two fluid flows through
alternate channels. The heat is transferred through the thin plate between the channels,
and creating complete counter current flow for highest possible efficiency. No
intermixing of the fluid or leakage to the surroundings will occur as gaskets around the
edges of the plates seal the unit. The corrugation of the plates provides a suitable
passage between the plates, support of each plate against the adjacent one and a strong
turbulence resulting in maximum heat transfer efficiency.
2
The plates provide each of the fluids with large heat transfer area because each
of the plates has a very large surface area. As a result a plate type heat exchanger
compared to a similarly sized of shell and tube heat exchanger, is capable of transferring
much more heat because of the larger area of the plates provides over tubes. Due to the
high heat transfer efficiency, plate type heat exchangers are usually very small when
compared to a shell and tube type heat exchanger but with the same heat transfer
capacity.
1.1.2 History of Plate Heat Exchanger
Based on document Plate and Frame Heat Exchanger (1986); Gary Hulbert
stated that the idea for designing plate heat exchanger was first developed by Dr.
Richard Seligman, the founder of the Aluminium Plant and Vessel Company Ltd in
1923. The company is now known worldwide as APV. Commercial development of the
plate heat exchanger resulted basically from the ability for high heat transfer rates at
low differential temperatures; which exactly the feature that makes the plate heat
exchanger so famous in geothermal applications. The original plate heat exchanger
consisted of cast gun metal plates enclosed in a frame which is similar to a filter press.
In the early 1930’s the introduction of pressed thin gauge stainless steel plates produced
a machine that has developed into modern plate and frame heat exchanger.
1.1.3 Heat Transfer
Heat transfer is a science that studies the energy transfer between two bodies due
to temperature difference. In theory, thermal energy is related to the kinetics energy of
molecules on a microscopic scale. When material’s temperature increases, the thermal
agitation of its constituent molecules will increase. Then the areas which contain greater
molecular kinetic energy will pass this energy to areas with less kinetic energy. So when
an object or fluid is at different temperature than its surroundings, the heat transfer will
occur in such a way that the body and the surroundings reach thermal equilibrium.
Generally there are three types of heat transfer which are conduction, convection
and radiation. Conduction is the transfer of heat within an object or between two objects
3
in contact. Convection heat transfer occurs when a fluid (liquid or gas) comes in contact
with a material of a different temperature. For natural convection, it occurs when the
flow of a fluid is primarily due to density differences within the fluid due to cooling or
heating of that fluid. Meanwhile, forced convection occurs when the flow of fluid is
primarily due to pressure differences. Radiation is the transfer of heat from one object to
another by means of electro-magnetic waves. Radiation does not require objects to be in
contact or fluid flow between those objects, it occurs in the void of space (that’s how
the sun warms us). Transfer of thermal energy can also occur with any combination of
the three. In my study which relates to plate heat exchanger, it consists of heat transfer
by conduction and convection.
1.2 PROBLEM STATEMENT
Heat transfer is the most important parameter to be measured as the thermal
performance and heat transfer efficiency of the plate heat exchanger. As a comparison,
plate heat exchangers are competitive with shell and tube units because of high heat
transfer efficiency and attractive features even though built of costlier materials.
Besides that, many studies have been done using both experimental and numerical
analysis based on working fluid (water/water) which has small viscosity compared to
other types of fluid. In order to investigate more, fluid with higher viscosity should be
used to observe the outcome of heat transfer performance. By using CFD simulation,
the performance of plate heat exchanger can be optimized and at the same time, it can
reduce the operation cost and time when using experimental analysis.
4
1.3 OBJECTIVES
The objectives of this study are:
(i) To study the heat transfer performance of plate heat exchanger for heating
diesel with hot water
(ii) To observe which configurations and parameters that gives the best results
(iii) To study and modeling the heat transfer of plate heat exchanger using CFD
simulation
1.4 SCOPES OF STUDY
In order to achieve the objectives above, there are five scopes of this study defined
which are:
(i) The working fluid used for this study are diesel and water
(ii) There are two parameters that will be the manipulated variables which are
temperature and velocity
(iii) Both parameters above will be investigated in term of their effect using two
kind of distinct configurations which is series and parallel; both counter-
current
(iv) The study concerned with turbulent flow regimes using k-ε equation
(v) The application of CFD simulation to model the heat transfer and to compare
which configuration is a better choice
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CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
The purpose of this chapter is to provide a literature review of past research
effort such as journals or articles or documents related to heat transfer of plate heat
exchanger experimentally and numerically. In addition, review of other relevant
research studies are made to provide additional information in order to understand more
of this study.
2.2 PLATE HEAT EXCHANGER
Nowadays, plate heat exchangers are used widely as a better choice for higher
efficiency in thermal performance. As stated by H. Dardour, S. Mazouz, A. Bellagi,
(2009), in the majority of the industrial applications, the plate heat exchanger is the
design of choice because of its characteristics which are easy-to-maintain, compact
design, light weight and because of the many advantages it offers. Minimal
maintenance, cost effectiveness and especially high efficiency are the most important
criteria that are making studies on plate heat exchanger is a big challenge for researchers
to develop and produce plate heat exchanger achieving the best possible performance in
terms of efficiency and economical considerations.
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2.2.1 Performances of Plate Heat exchanger
Before this, plate type heat exchangers are not widely used because of the
inability to seal the large gaskets between each of the plates. Because of this problem,
plate type heat exchangers have only been used in small, low pressure applications.
Nevertheless, new improvements have been made in gasket design and overall heat
exchanger design to allow some large scale applications of the plate type heat
exchanger. As the developments arise, large plate type heat exchangers are replacing
shell and heat exchangers and becoming more common.
The PHE consists of a pack of gasketed corrugated metal plates, pressed
together in a frame. The gaskets on the corners of the plates form a series of parallel
flow channels, where the fluids flow alternately and exchange heat through the thin
metal plates. The number of plates, their perforation, the type and position of the
gaskets and the location of the inlet and outlet connections at the covers characterize the
PHE configuration, which further defines the flow distribution inside the plate pack.
The flow distribution can be parallel, series or any of their various possible
combinations. (Jorge A.W. Gut, Jose M. Pinto 2003). From Figure 2.1, it shows the
basic flow principle of plate heat exchanger in parallel.
Figure 2.1: Flow Principle of Plate Heat Exchanger
Source: Heat Exchanger Engineering Techniques book, Michael J. Nee
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Li Xiao-wei and Meng Ji-an and Li Zhi-xin stated that plates are the basic heat
transfer elements in plate heat exchangers, so the basic way to improve the performance
of plate heat exchangers is to improve the flow and heat transfer performance of the
plates. The best plates should have high heat transfer coefficients, low pressure drop and
high pressure endurance. In this study, the heat transfer performance will be
investigated for heating the diesel using hot water system. The best configurations will
be selected based on the heat transfer performance. The heating process is necessary to
maintain better flow ability of diesel in diesel engine. The flow ability of diesel will be
worse as soon as the temperature started to decrease because of the high viscosity of
diesel.
2.2.2 Advantages and Disadvantages
From Heat Exchanger Engineering Techniques, Michael J. Nee stated plate heat
exchangers are preferred over shell and tube heat exchangers in some applications. They
are well suited to counter flow construction, thus maximizing the Log Mean
Temperature Difference (LMTD) correction factor. Their construction minimizes the
need for welding. Plate heat exchangers often have a competitive advantage when the
available pressure drop is high (5 to 10 psi) and when most of it is used in selecting heat
exchanger. The reason is the plate heat exchanger is relatively short length of travel.
In the mean time, the turbulent flow inside will help to reduce deposits which
would interfere with heat transfer. Its pluses are that it occupies high heat transfer
efficiency, less space, simple in maintenance and easily cleaned on both streams. Plate
heat exchanger required no extra space for dismantling and its capacity can be increased
by introducing plates in pairs. Therefore, when corrosion is an issue, the plate heat
exchangers have more advantage because it is manufactured with stainless steel. Due to
the plate thicknesses are thinner resulting in a decrease in metal resistance. Besides that,
the herringbone shape breaks up any laminar or transition flow component present thus
acting like a turbulator. The conditions are additive in improving the heat transfer rate.
Moreover, these pluses can and often occur on both streams.
8
On the other hand, there are also several disadvantages of plate heat exchangers;
the main objection is the possibility of leakage. Plate heat exchangers are not available
with extended surface other than that of stretching occurs in the stamping process. They
are not recommended when fluid particles are larger in diameter than the stamped depth
of the plates. The pressure and temperature limits are low when compared to shell and
tube units, roughly 400 psi and 375°F. Besides that, plate heat exchangers are not
readily adaptable to low pressure vapor or gas. In general, the plate heat exchangers are
less efficient in high fouling services and made from costlier materials.
2.2.3 Numerical Analysis for Co-Current
H. Dardour, S. Mazouz, A. Bellagi, (2009) presented an analysis paper of co-
current plate heat exchanger and its numerical simulation results. From known data
which are the hot and cold fluid streams inlet temperatures, heat capacities and overall
heat transfer coefficients, a 1-D mathematical model based on the steady flow energy
balance for a differential length of the device is developed resulting in a set of N first
order differential equations with boundary conditions where N is the number of
channels.
For specific heat exchanger geometry and operational parameter, the problem is
numerically solved using the shooting method. This simulation allows the prediction of
the temperature map in the heat exchanger and the evaluation of its performances. A
parametric analysis is performed to evaluate the influence of the R-parameter on the ε-
NTU values. For practical purposes, the effectiveness-NTU graphs are elaborated for
specific heat exchanger geometry and different operating conditions.
2.2.4 Experimental and Numerical Heat Transfer
Flavio C.C. Galeazzo, Raquel Y. Miura, Jorge A.W. Gut, Carmen C. Tadini,
(2006) studied a four-channel plate heat exchanger developed by using CFD as shown
in Figure 2.2 and Figure 2.3. There were two kinds of arrangements that have been
tested which are parallel and series, both counter-currents. From Figure 2.4 and Figure
2.5, the distributions are shown in term of temperature and velocity, which lead to
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comparison between numerical predictions and experimental results for heat load
obtained from 1D plug-flow model and 3D CFD model. The experimental procedure
was conducted using water as working fluid on hot and cold sides of plate heat
exchanger.
Figure 2.2: (a) The plate pack of the PHE used in this study, (b) The CFD
representation of the fluid domain for series flow arrangement showing a mesh detail
Source: Flavio C.C. Galeazzo, Raquel Y. Miura, Jorge A.W. Gut, Carmen C. Tadini,
(2006)
Figure 2.3: Expanded CFD representation and opened plate pack for (a) parallel
arrangement and (b) series arrangement
Source: Flavio C.C. Galeazzo, Raquel Y. Miura, Jorge A.W. Gut, Carmen C. Tadini,
(2006)
10
Figure 2.4: Midplane temperature distribution for the channels of a series flow
arrangement: 3D and 1D model results
Source: Flavio C.C. Galeazzo, Raquel Y. Miura, Jorge A.W. Gut, Carmen C. Tadini,
(2006)
Figure 2.5: Midplane velocity distribution for the channels of a series flow
arrangement: 3D and 1D model results
Source: Flavio C.C. Galeazzo, Raquel Y. Miura, Jorge A.W. Gut, Carmen C. Tadini,
(2006)
11
For CFD part, the sensitivity of the simulation to the turbulence modeling was
investigated and solved using laminar flow model, k-ε turbulence model with wall
functions and the k-ε turbulence model with enhanced wall treatment. Most flow inside
the exchanger was verified as laminar; however there were turbulent regions especially
near the plate ports. In order to correctly model the flow and heat transfer, the k-ε
turbulence model with enhanced wall treatment model was preferred and have way
better agreement with the experimental results.
2.2.5 Modeling with Generalized Configurations
S.G. Kandlikar and R.K. Shah (1989) developed a method to calculate an
approximate thermal effectiveness for large exchangers, where the effects of the end
plates and the changes of passes are less significant and thus can be neglected. The
analytical solution of the system of equations in matrix form was studied by T. Zaleski
and A.B. Jarzebski (1973) for exchangers with series and parallel flow arrangements.
Since this solution for the method may lead to numerical problems on the calculation, it
is not recommended to exchangers with large number of channels. S.G. Kandlikar and
R.K. Shah (1989) and M.C. Georgiadis and S. Macchietto (2000) has used the finite
difference method for the simulation of plate heat exchangers. They have simulated and
compared using several configurations. Then it was verified that higher effectiveness is
achieved when the exchanger is symmetrical (both streams with the same number of
passes) with the passes arranged for counter current flow in the channels. The same
results were obtained by T. Zaleski and K. Klepacka (1992) when analyzing the thermal
effectiveness of various plate heat exchanger configurations.
Jorge A.W. Gut and Jose M. Pinto (2003) presented a plate heat exchanger
modeling framework that is suitable for any configuration. The purpose of developing
the model is to study the influence of the configuration on the exchanger performance.
The study for variation of the overall heat transfer coefficient throughout the exchanger
with respect to the assumption of a constant value is also investigated. The
mathematical modeling of a plate heat exchanger is developed in algorithmic form.
Finally a simulation example is shown, where the effect of the assumption of constant
overall heat transfer coefficient is analyzed.
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2.2.6 Effectiveness Charts for Counter Flow Corrugated
Harika Sammeta, Kalaichelvi Ponnusamy, M.A. Majid. K. Dheenathayalan,
(2011) prepared analysis charts for 9-plate counter flow corrugated plate heat exchanger
which is modeled and simulated using CFD. The performance of the plate heat
exchanger is analyzed using the obtained simulated data in the form of charts such as
effectiveness, ε versus number of transfer units, NTU at constant capacity ratio, R and
so on. The problem was numerically solved using the finite volume method with
FLUENT and Figure 2.6 shows how the results of temperature contours looks like.
From this paper, it is observed that the temperature difference for counter flow agrees
with the fundamental concepts of counter flow heat exchangers.
Figure 2.6: Temperature contours of 0.005 kg/s hot flow rate for various cold flow rates
Source: Harika Sammeta, Kalaichelvi Ponnusamy, M.A. Majid. K. Dheenathayalan,
(2011)
13
2.2.7 Heat Transfer Fouling and Fluid Flow
Kho and Müller-Steinhagen (1999) investigated the effect of flow distribution
inside the channel of a plate heat exchanger with flat plates. CFD simulations were
performed using CFX (ANSYS, Canonsburg, USA). Different distributors were tested
numerically for obtaining a more homogeneous flow distribution and thus reducing
fouling. The geometry of the channel was modeled with grid of 45,000 elements using
the k-ε turbulence model. The plate wall temperature was specified as boundary
condition and flow and heat transfer were simulated for incompressible flow under
steady state conditions. As shown in Figure 2.7, the results of contours are obtained by
using four different kinds of distributions.
Figure 2.7: Flow and temperature distribution for distributor design C, G and H
Source: Kho and Müller-Steinhagen (1999)
2.2.8 Effect of Flow Arrangement on the Pressure Drop
The pumping power is an important constraint for the design of plate heat
exchanger which is proportional to the pressure drop. Moreover, plate heat exchangers
have pressure limitations due to the extensive use of gaskets; thus, the maximum
pressure is also a design constraint that depends on the pressure drop. This investigation
has been done by Raquel Y. Miura, Flavio C.C. Galeazzo, Carmen C. Tadini, Jorge
A.W. Gut (2008) in order to study the effect of flow arrangement on the pressure drop.