AN EXPERIMENTAL DESIGN & ANALYSIS OF PORTABLE USB POWERED THERMO ELECTRIC COOLER

AN EXPERIMENTAL DESIGN & ANALYSIS OF PORTABLE
USB POWERED THERMO ELECTRIC COOLER
A Major Project Report Submitted
In partial fulfillment of the requirements for the award of the degree of
Master of Technology
In
Thermal Engineering
by
NAVATE PRANAV 18N31D2110
Under the guidance of
DR.P.SRIKAR
Professor
Department of Mechanical Engineering
Malla Reddy College of Engineering & Technology
(Autonomous Institution- UGC, Govt. of India)
(Affiliated to JNTUH, Approved by AICTE, NBA &NAAC with ‘A’ Grade)
Secunderabad – 500100, India
www.mrcet.ac.in
2018-2020

i
AN EXPERIMENTAL DESIGN & ANALYSIS OF PORTABLE
USB POWERED THERMO ELECTRIC COOLER
NAVATE PRANAV 18N31D2110
MASTER OF TECHNOLOGY
THERMAL ENGINEERING
2018-2020
Malla Reddy College of Engineering and Technology
UGC Autonomous, NBA Accredited, Approved by AICTE, Affiliated to JNTUH

ii
AN EXPERIMENTAL DESIGN & ANALYSIS OF PORTABLE USB
POWERED THERMO ELECTRIC COOLER
A Major project report submitted in partial fulfillment of the requirements for the
degree of Master of Technology in Thermal Engineering.
By
Navate Pranav (18N31D2110)
Under the guidance of
DR. P.SRIKAR
Professor
Malla Reddy College of Engineering and Technology
UGC Autonomous, NBA Accredited, Approved by AICTE, Affiliated to JNTUH
Secunderabad – 500100, Telangana, India.
2018 - 2020

iii
MALLA REDDY COLLEGE OF ENGINEERING & TECHNOLOGY
Autonomous Institution - UGC Govt. of India
(Affiliated to JNTU, Hyderabad, Approved by AICTE - Accredited by NBA & NAAC – ‘A’ Grade)
Secunderabad – 500100, Telangana State, India
CERTIFICATE
This is to certify that the Major Project work entitled “AN EXPERIMENTAL DESIGN &
ANALYSIS OF PORTABLE USB POWERED THERMO ELECTRIC COOLER” is carried out by
NAVATE PRANAV (H.T.NO. 18N31D2110), in partial fulfillment for the award of degree
of MASTER OF TECHNOLOGY in THERMAL ENGINEERING, Jawaharlal Nehru
Technological University, Hyderabad during the academic year 2019-2020.
Prof. Dr. P.Srikar Prof. Dr. A. N. R. Reddy
Internal Guide Head of the Department
External Examiner

iv
DECLARATION
I hereby declare that the project titled “An Experimental Design and Analysis of
Portable USB Powered Thermo Electric Cooler” submitted to Malla Reddy College of
Engineering and Technology (UGC-Autonomous), affiliated to Jawaharlal Nehru
Technological University Hyderabad (JNTUH) for the award of the degree of Master of
Technology in Thermal Engineering is a result of original research carried-out in this
thesis. I understand that my report may be made electronically available to the public. It
is further declared that the project report or any part thereof has not been previously
submitted to any University or Institute for the award of degree or diploma.
Name of the Student : Navate Pranav
Hall Ticket Number : 18N31D2110
Degree : Master of Technology in Thermal Engineering
Department : Mechanical Engineering
Title of the project : An Experimental Design and Analysis of Portable USB
Powered Thermo Electric Cooler
_________________________________
(Navate Pranav)
Date:

v
DEDICATION
This work is dedicated to “Department of Mechanical Engineering- Malla Reddy College
of Engineering and Technology (UGC-Autonomous)”.
-o0o-

vi
ACKNOWLEDGEMENT
I deeply thankful to our respected Principal of the College (MRCET) Dr. VSK Reddy
and Head of the Department (Mech) Dr. Amarnath Reddy, Professor of Thermal
Dept and our internal guide Dr. P.Srikar, whose help and interest where always with us
during the execution of the project.
Finally, I want to deeply acknowledgement all my classmates, friends, and family
members who have encouraged me during the preparation of my project.

vii
ABSTRACT
Refrigerators are energy consuming home appliances and for this reason researchers are
performed to enhance performance work of the refrigeration systems. Most of research
work done so far deals with an objective of low energy consumption and refrigeration
enchantment. Thermoelectric refrigeration is one of the techniques to produce
refrigeration effect. This project demonstrates how far thermoelectric refrigeration can be
modified to produce refrigeration effect with low power input and high cooling effect.
In this project a portable thermoelectric (Peltier) cooler is designed and fabricated for
multipurpose use (Like beverage cooling, water cooling, and milk storage). It is operated
on USB with low power, portable in nature and compact in seize. This project carries out
cooling effect analysis, steady state heat transfer finite element analysis on different
water bottle materials with different heat transfer plates, thermal insulation jacket in
ANSYS R19 workbench. Power consumption of this device and its performance is
experimented and calculated with practical model on DC-DC to boost converter, also
TEC inter components CFD analysis done in ANSYS Fluent.
Keywords: Peltier Module, USB, DC-DC Boost Converter, Heat Transfer Plates,
Thermal insulation Jacket, Steady State Heat Transfer Finite Element Analysis, CFD
Analysis, ANSYS Fluent.

viii
TABLE OF CONTENTS
Page
Certificate from MRCET iii
Declaration iv
Dedication v
Acknowledgement vi
Abstract vii
Table of Contents viii
List of Tables xv
List of Figures xviii
List of Abbreviations xxiii
Greek Symbols xxv
CHAPTER 1: INTRODUCTION 1
1.1 Introduction 1
1.2
1.3
Operating principle
Problem statement
2
2
1.4 Solution for the problem 3
1.5 Scope of research 3
1.6 Research hypothesis 3
1.7 Objectives 4
1.8 Organization of the report 4
CHAPTER 2: LITERATURE REVIEW 5
2.1 Background 5
2.2 Working of TEC 5

ix
2.3 Choosing materials 6
2.4 TEC Construction 7
2.5 Thermoelectric Effect 7
2.5.1 Seebeck Effect 8
2.5.2 Peltier Effect 8
2.5.3 Thomson Effect 9
2.5.4 Joulean Effect 9
2.5.5 Conduction Effect 10
2.6 Exergy 10
2.7 Benefits of TEC 11
2.8 State of Art Review 12
2.8.1 Performance Investigation 12
2.8.2 Power for TEC 12
2.8.3 TEC as a Hybrid System 13
2.8.4 Optimization of TEC 14
2.8.5 Single-stage and Multi-stage TEC 16
2.8.6 Feasibility Study of TEC 17
2.9 Thermo Economics 19
2.10 Recent Developments in Thermo Electrics 21
2.11 Gaps and Opportunities 29
CHAPTER 3: MATERIAL AND METHODOLOGY 30
3.1 FEM of TE Element’s 30
3.1.1 Preparation of the TE CAD model 30
3.1.2 Geometry 31
3.1.3 Material for Peltier Module 31

x
3.1.4 Meshing and Simulation 33
3.1.5 Applying Boundary Conditions 34
3.1.6 Solution 34
3.1.6.1 Temperature Distribution 34
3.1.6.2 Heat Flux Distribution 35
3.1.6.3 Total Current Density and Direction 35
3.1.6.4 Total Electric Field Intensity and Direction 36
3.1.6.5 Joule Heat 37
3.2 TEC Theoretical Calculations 37
3.2.1 Analysis of Thermoelectric Cooling 37
3.2.2 Coefficient of Performance (COP) 37
3.2.3 Load Calculations 40
3.2.3.1 Heat Load 41
3.2.3.1.1 Active Heat Load 41
3.2.3. 1.2 Radiation 41
3.2.3. 1.3 Convection 41
3.2.3. 1.4 Conduction 42
3.2.3. 1.5 Transient 42
3.2.4 Entire Assembly of Peltier Module 43
3.3 Preparation of heat sink CAD Model 44
3.3.1 Material Selected For Heat Sink 44
3.3.1.1 Heat Sink Dimensions 44
3.3.2 Heat Transfer Principle 45
3.3.3 Assumptions for Thermal Analysis of Heat Sink 48
3.3.3.1 Heat Transfer Coefficient (h) 48

xi
3.3.4 FEM of Heat Sink 49
3.3.4.1 Preparation of the Design Model 49
3.3.4.2 Geometry of Heat Sink 50
3.3.4.3 Mesh Generation & Simulation 50
3.3.4.4 Loading Boundary Conditions 51
3.3.4.5 Solution 51
3.3.4.5.1 Temperature Distribution 52
3.3.4.5.2 Heat Flux Distribution& Direction 53
3.4 Axially Curved Cooling Fan Design 53
3.4.1 Axial Fan CAD Model 55
3.4.2 Numerical Analysis 56
3.4.2.1 The Standard k-ε Model 56
3.4.2.2 Grid System 57
3.4.2.3 Boundary Conditions 58
3.4.2.4 Solution 60
3.4.2.4.1 Velocity and Pressure Contours 60
3.4.2.4.2 Eddy Viscosity and Turbulence Kinetic
Energy Contours
61
3.4.3 Electronic Power Monitoring System 63
3.4.3.1 Arduino UNO R3 63
3.4.3.1.1 ATMEGA328P-PU Microcontroller 64
3.4.3.2 Analog NTC Thermistor Module 66
3.4.3.3 Arduino Embedded Code For Axial Fan PWM
Signal Control
70
3.4.3.4 PWM Operations 71

xii
3.4.3.4.1 PWM Control Input Signal 71
3.4.3.4.2 PWM Control Output Signal 72
3.4.3.4.3 Fan Speed Control 72
3.4.3.4.3.1 Minimum RPM 73
3.4.3.4.3.2 Fan Speed Response to PWM
Control Input Signal
73
3.5 Forced Convection Heat Transfer Analysis 74
3.5.1 Governing Equations in CFD 75
3.5.2 Assumptions 76
3.5.3 Problem Solving in ANSYS 76
3.5.3.1 Pre-processing 76
3.5.3.2 Solver Setup 78
3.5.3.2 Post-processing 79
3.6 DC-DC Boost Step-up Module 87
3.6.1 400 kHz 15V, 4A Switching Current Booster/Inverting
Converter (XL6009)
87
3.6.1.1 Pin Configurations 88
3.6.1.2 Circuit Layout 89
3.6.1.3 XL6009 Electrical Characteristics 90
3.6.1.4 Features 92
3.6.2 Input USB Series Connector/Charge Module 93
3.6.2.1 TP4056 Lithium Battery Series Connector Board
with Over-current Protection 18650 Micro USB
93
3.6.2.2 Electrical Characteristics Setting 96
3.6.2.3 Features 96

xiii
3.6.3 S-8254A Battery Protection Module for 4 - Cell Pack 97
3.6.3.1 Operation of S-8254A 100
3.6.3.1.1 Normal Status 100
3.6.3.1.2 Overcharge Status 101
3.6.3.1.3 Overdischarge Status 101
3.6.3.1.3.1 Power-down Function 101
3.6.3.1.3.2 Overcurrent Status 102
3.6.3.1.3.3 0 V Battery Charge 103
3.6.3.1.3.4 Delay Time Setting 103
3.6.3.1.3.5 CTL Pin 103
3.6.3.1.3.6 SEL Pin 104
3.6.3.2 Features 104
3.6.4 Final Assembly of DC-DC Series Booster 106
3.7 Final Device Design 108
3.8 Practical Calculations 109
3.8.1 Practical Test Conditions (with heat sink-without cooling fan)
in case-1
110
3.8.1.1 Load Calculations 110
3.8.2 Practical Test Conditions (with heat sink-with cooling fan)
Test Condition (case-2)
111
3.8.2.1 Load Calculations
3.9 Preparing of Complete TEC Device with Thermal Jacket 113
3.9.1 CAD Model & Geometry Details of TEC with Thermal Jacket 113
3.9.2 Materials used for Simulation 114
3.9.3 Meshing 115

xiv
3.9.4 Boundary Conditions Loading 116
3.9.5 Solution 116
3.9.5.1 PET Bottle Temperature and Heat Flux Simulation
(without H.T Plates)
117
3.9.5.2 Aluminium Bottle Temperature and Heat Flux Simulation 117
3.9.5.3 Copper Bottle Temperature and Heat Flux Simulation 118
3.9.5.4 PET Water Bottle Temperature and Heat Flux Simulation
(with Thermal Jacket & Heat Transfer Plates)
118
CHAPTER 4: RESULTS AND DISCUSSION 120
4.1 TEC Performance Analysis Test-1 120
4.1.1 TEC Standard Performance Curves at (Th=27 0
C) 120
4.1.2 TEC standard performance curves at (Th=50 0
C) 124
4.2 TEC Performance Analysis Test-2 129
4.3 Cost of Overall Project 134
4.4 Summary of Results and Discussion 135
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 136
5.1 Conclusion 136
5.2 Recommendations 136
REFERENCES 137
APPENDICES 140
Appendix (Publications) 140

xv
LIST OF TABLES
Page
Table 3.1 TEC module material properties 33
Table 3.2 Acceptable temperatures 41
Table 3.3 Typical values of convection heat transfer coefficient 42
Table 3.4 Bi2Te3 TEC module practical parameters observations at 210
C 43
Table 3.5 Heat sink material properties 44
Table 3.6 Properties of AL2O3 (TE Ceramic base plate) 50
Table 3.7 Properties of air 50
Table 3.8 Axially curved cooling fan software observations 63
Table 3.9 Axially curved cooling fan practical observations 63
Table 3.10 Temperature verses NTC 200  thermistor resistance variation 67
Table 3.11 Thermistor resistance vs. Sensor value 69
Table 3.12 PWM output parameter 74
Table 3.13 Values of function parameters inside enclosure on ZX-plane 84
Table 3.14 Simulation values of heat sink on variation of no. of fins 86
Table 3.15 RPM vs. fin temperature variation practical observations 87
Table 3.16 T0263-5L pin description 88
Table 3.17 XL6009 absolute maximum ratings 89
Table 3.18 XL6009 electrical characteristics 90
Table 3.19 Electrical characteristics (DC Parameters). 91
Table 3.20 Schottky diode selection 91
Table 3.21 RProg current setting 96
Table 3.22 S-8254A pin description 97

xvi
Table 3.23 Parameters of BMS circuit 99
Table 3.24 Conditions set by CTL pin 103
Table 3.25 Conditions set by SEL pin 104
Table 3.26 DC-DC series booster/inverter power parameters 107
Table 3.27 Input and output power specifications 108
Table 3.28 Test parameters based on DC-DC boost converter 109
Table 3.29 PVC (plasticized, flexible) material properties 115
Table 3.30 Water properties 115
Table 3.31 PET material properties 115
Table 4.1 Shows performance observation of cooling load (W) and
Temperature difference between ambient and hot side of the
module (DT/0
C), Current (A)
120
Table 4.2 Shows performance observation of voltage (V) and Temperature
difference between ambient and hot side of the module (DT/0
C),
Current (A)
121
Table 4.3 Shows performance observation of cooling load (W) and voltage
(V), DT (0
C)
121
Table 4.4 Shows performance observation of voltage (V) and change in
temperature DT (0
C), C.O.P
122
Table 4.5 Overall performance of TEC at ambient 270
C 124
Table 4.6 Shows performance observation of cooling load (W) and
Temperature difference between ambient and hot side of the
module (DT/0
C), Current (A)
124
Table 4.7 Shows performance observation of voltage (V) and Temperature
difference between ambient and hot side of the module (DT/0
C),
125

xvii
Current (A)
Table 4.8 Shows performance observation of cooling load (W) & voltage
(V), DT (0
C)
126
Table 4.9 Shows performance observation of voltage (V) and change in
temperature DT (0
C), C.O.P
127
Table 4.10 Overall performance of TEC at ambient 500
C 128
Table 4.11 Standard Performance specification sheet of TEC from experiment 128
Table 4.12 TEC without cooling fan practical observations 129
Table 4.13 TEC with cooling fan practical observations 130
Table 4.14 Fin cooling rate depending upon fan speed 131
Table 4.15 Practical observation readings of 1000ml PET water bottle which
covered with thermal jacket and Al heat transfer plates
132
Table 4.16 Practical observation readings of 1000ml aluminium water bottle
cooling
133
Table 4.17 Practical observation readings of 1000ml copper water bottle 133
Table 4.18 Component price specification 134

xviii
LIST OF FIGURES
Page
Figure 1.1 Working principle 2
Figure 2.1 TEC construction 7
Figure 2.2 Behaviour of single and multistage TEC’s 16
Figure 3.1 2D and 3D model of Peltier module TE couples 31
Figure 3.2 ZT for P-type thermoelectric materials 32
Figure 3.3 ZT for N-type thermoelectric material 32
Figure 3.4 Meshing TE module model 33
Figure 3.5 Loading boundary condition for TE elements 34
Figure 3.6 Temperature distribution in TE element 35
Figure 3.7 Total heat flux distribution of TE element 35
Figure 3.8 Total current density and direction 36
Figure 3.9 Total electric field intensity and directional electric field intensity 36
Figure 3.10 Joule heat 37
Figure 3.11 Bi2Te3 TE Module of 127 thermocouples 44
Figure 3.12 Sectional and side view of heat sink 45
Figure 3.13 Heat sink 3D isometric view 45
Figure 3.14 Heat thermal resistance configuration 46
Figure 3.15 Sketch of a heat sink in a duct used to calculate the governing
equations from conservation of energy and Newton’s law of cooling
48
Figure 3.16 Meshing and element quality of the heat sink model (1mm) 51
Figure 3.17 Loading and boundary conditions and convection 51
Figure 3.18 Temperature distribution over heat sink (isometric view) 52

xix
Figure 3.19 Temperature distribution simulation in different views 52
Figure 3.20 Heat flux and Directional heat flux (x-axis) distribution simulation 53
Figure 3.21 Airflow mechanism in an axial fan 54
Figure 3.22 Dimensional sketch of axial fan 55
Figure 3.23 3D sketch of axial fan 56
Figure 3.24 3D sketch of axial fan fluid flow in enclosure 57
Figure 3.25 3D Grid meshing of axial fan 58
Figure 3.26 Simulation parameters 59
Figure 3.27 Graph of Residuals v/s No. of iterations 59
Figure 3.28 Set lines in YZ-axis 60
Figure 3.29 Velocity stream lines and contours in enclosure 60
Figure 3.30 Velocity graph in Y- Axis 61
Figure 3.31 Velocity on axial fan hub and blades in different places in XY-plane 61
Figure 3.32 Eddy current viscosity and turbulence kinetic energy contours 62
Figure 3.33 Graph of Turbulence kinetic energy 62
Figure 3.34 Arduino UNO R3.0 board 64
Figure 3.35 ATMEGA328P-PU pin configuration 66
Figure 3.36 NTC Thermistor sensor 66
Figure 3.37 Graph of typical resistance as a function of temperature for an NTC
temperature sensor
67
Figure 3.38 NTC module circuit diagram 68
Figure 3.39 Power monitoring system circuit diagram 69
Figure 3.40 Graph of sensor value vs. PWM O/P signal 71
Figure 3.41 Graph of PWM duty cycle 72
Figure 3.42 Graph of minimum fan speed requirements: Start pulse 73

xx
Figure 3.43 Graph of fan speed response to PWM control input signal 73
Figure 3.44 Fin in rectangular enclosure 77
Figure 3.45 Meshing fin in enclosure 77
Figure 3.46 Simulation parameters 78
Figure 3.47 Graph of Residuals vs. no. iterations 79
Figure 3.48 Air velocity 1m/s with turbulent air flow 79
Figure 3.49 Air velocity 2m/s with turbulent air flow 80
Figure 3.50 Air velocity 4.2m/s with turbulent air flow 80
Figure 3.51 Air velocity 4.8m/s with turbulent air flow 80
Figure 3.52 Graph of temperature vs. air velocity 81
Figure 3.53 Air velocity variation graph on fin surface 81
Figure 3.54 Pressure variation graph on fin surface 82
Figure 3.55 Contours of optimized solution in ZX- plane at distance (1mm) 82
Figure 3.58 Velocity stream lines of air on complete heat sink 85
Figure 3.59 Volume rendering of heat sink at air velocity 2m/s 85
Figure 3.60 Number of fins vs. sink temperature 86
Figure 3.61 Package type of XL6009 88
Figure 3.62 Pin configuration of T0263-5L (TopView) 88
Figure 3.63 Function block diagram of XL6009 89
Figure 3.64 XL6009 Typical application circuit (Boost Converter) 89
Figure 3.65 XL6009 DC-DC boost converter on PCB 92
Figure 3.66 TP4056 IC pin layout 94
Figure 3.67 Circuit diagram 95

xxi
Figure 3.68 TS4056 Mini USB series connector 97
Figure 3.69 S-8254A IC pin layout 97
Figure 3.70 BMS circuit diagram 99
Figure 3.71 S-8254A 4S-BMS Module 104
Figure 3.72 2D view of DC-DC series booster 106
Figure 3.73 Block diagram of DC-DC series booster 107
Figure 3.74 Final CAD model of DC-DC series booster/inverter device 107
Figure 3.75 Graph of output voltage vs. current of DC-DC series booster 108
Figure 3.76 Final electric connection block diagram of TEC 109
Figure 3.77 Complete design 109
Figure 3.78 Dimensions of water bottle with H.T plates and thermal jacket 113
Figure 3.79 3D model of TEC with Al H.T plates and thermal jacket 114
Figure 3.80 Meshing Al H.T plates and thermal jacket with water bottle 116
Figure 3.81 Boundary conditions of water bottle with Al plates and thermal
jacket
116
Figure 3.82 PET bottle temperature and heat flux Simulation (without H.T
plates)
117
Figure 3.83 Al bottle temperature and heat flux simulation (without heat transfer
plates)
117
Figure 3.84 Cu water bottle temperature and heat flux Simulation 118
Figure 3.85 PET bottle temperature and heat flux Simulation with Al H.T plates 118
Figure 3.86 PET bottle temperature and heat flux Simulation with Cu H.T plates 119
Figure 3.87 Final practical working model 119
Figure 4.1 Performance Graph QC= f (DT) 120
Figure 4.2 Performance Graph V= f (DT) 121

xxii
Figure 4.3 Performance Graph QC= f (V) 122
Figure 4.4 Performance Graph QC= f (V) of DT ranged from 0 to 30 0
C 123
Figure 4.5 Performance Graph COP = f (V) of DT ranged from 40 to 60 0
C 123
Figure 4.6 Performance Graph QC= f (DT) 125
Figure 4.7 Performance Graph V= f (DT) 125
Figure 4.8 Performance Graph QC= f (V) 126
Figure 4.9 Performance Graph QC= f (V) of DT ranged from 0 to 30 0
C 127
Figure 4.10 Performance Graph COP= f (V) of DT ranged from 40 to 70 0
C 128
Figure 4.11 Graph of TEC (without cooling fan) change in temp vs. time 130
Figure 4.12 Graph of TEC (with cooling fan) change in temp vs. time 131
Figure 4.13 Graph of Air flow vs. Fin temp 132

xxiii
LIST OF ABBREVIATIONS
A Area (mm2
)
g Gravitational acceleration, m/s2
h Convection heat transfer coefficient, [Wm-2
K-1
]
k Thermal conductivity, W/(m・K)
L Characteristic length, mm
P Pressure, Pa
q. Heat flux (W/m2
)
Q Heat load (W)
R Ideal gas constant
Rb Base thermal resistance (K/W)
Rf Fin thermal resistance (K/W)
Rt Total Thermal resistance (K/W)
T Temperature, K
Tc Cold side temperature (°C/K)
Th Hot side temperature (°C/K)
Tin Inlet temperature (°C/K)
ν Kinematic viscosity, m2
/s
V Voltage
Z Figure of merit [1/K]
Al Aluminum
Cu Copper
DC Direct Current
Gr Grashof Number

xxiv
Nu Nusselt Number
Pr Prandtl Number
Ra Rayleigh Number
Re Reynolds Number
Rth Specific thermal resistance, (0
C/W)
Tout Outlet temperature( °C/K)
CFD Computational Fluid Dynamics
C.O.P Coefficient of Performance
PET Polyethylene terephthalate
TEC Thermo Electric Cooler
u, v, w Velocity components, m/s

xxv
GREEK SYMBOLS
ΔTHot Temp. Difference rise above ambient temperature, K
ΔTCold Temp. Difference fall below ambient temperature, K
α Seebeck coefficient [VK-1]
ϕ Dimensionless refrigeration effect
μ Viscosity, kg/(s・m)
ρ Density, kg/m3.
T∞ Ambient temperature (°C/K)

1
CHAPTER 1
INTRODUCTION
1.1. Introduction
Conventional refrigerators consist of bulky moving parts like compressor, pump and
condenser which consume a lot of energy. The invention and use of non-conventional
alternatives has been effective to a great extent due to the numerous researches employed
towards the design and development of green energy sources. Thermoelectric
refrigeration has been through a topic of research interest for more than a decade now.
Recent advancements in the field include improvement of thermoelectric materials
with Peltier to create a heat flux at the junction of two different types of materials. A
Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat
pump which transfers heat from one side of the device to the other, with consumption
of electrical energy, depending on the direction of the current. Such an instrument is also
called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric
cooler (TEC). It can be used either for heating or for cooling, although in practice the
main application is cooling. It can also be used as a temperature controller that either
heats or cools.
This technology is far less commonly applied to refrigeration than vapor-compression
refrigeration is. The primary advantages of a Peltier cooler compared to a vapor-
compression refrigerator are its lack of moving parts or circulating liquid, very long life,
invulnerability to leaks, small size, and flexible shape. Its main disadvantages are high
cost for a given cooling capacity and poor power efficiency. Many researchers and
companies are trying to develop Peltier coolers that are cheap and efficient. A Peltier
cooler can also be used as a thermoelectric generator. When operated as a cooler, a

2
voltage is applied across the device, and as a result, a difference in temperature will build
up between the two sides. When operated as a generator, one side of the device is heated
to a temperature greater than the other side, and as a result, a difference in voltage will
build up between the two sides (the Seebeck effect). However, a well-designed Peltier
cooler will be a mediocre thermoelectric generator and vice versa, due to different design
and packaging requirements.
1.2. Operating Principle
Thermoelectric coolers operate by the Peltier effect (which also goes by the more general
name thermoelectric effect). The device has two sides, and when a DC electric current
flows through the device, it brings heat from one side to the other, so that one side gets
cooler while the other gets hotter. The "hot" side is attached to a heat sink so that it
remains at ambient temperature, while the cool side goes below room temperature. In
some applications, multiple coolers can be cascaded together for lower temperature.
Fig. 1.1: Working principle.
1.3. Problem Statement
In portable thermo electric coolers for effective cooling it required good heat sink design
for large heat dissipation, high current flow across its P-N junction couples and easy to
portable body structure, optimized C.O.P. Due to this reasons portable thermo electric
refrigerators in small seize are still lack in market.

3
1.4. Solution for the Problem
In this project I’m going to design and experiment a effective heat sink with its proper
cooling system in compact seize, I’m going to fabricate and develop a DC to DC current
series step up circuit for boosting high current with low voltage, electronic power
monitoring circuit will be developed. Also thermal insulation jacket with heat transfer
plates will be prepared to insulate and increase effective cooling of PET water bottles
which mostly used in regular daily life.
1.5. Scope of Research
This device widely used in commercial applications like beverage cooling, water bottle
cooling, milk storage and medicine storage while travelling or in office use, domestic use
where space and energy matters a lot.
1.6. Research Hypothesis
Present research work was carried out in accordance with the following specific research
hypothesis:
1. It is hypothesized that the recognition of the right Peltier module with effective heat
sink and compact body design can produce required cooling in small space.
2. TEC can be made portable if design (small seize) and energy consumption is low.
3. PET water bottles are major issue in contact cooling due to its low thermal
conductivity; it can be solved by placing high conducting heat transfer plates around
bottle with replaceable design.
4. Preparation of thermal insulation jacket is another major advantage in PET and other
material water bottles for holding inside fluid cold temperature for long time.
5. Lastly DC-DC boost converter/inverter fabricated which runs on USB power (⎓5V).

4
1.7. Objectives
This research focuses on the following objectives
1. To design TE module and Heat sink, Refrigerator body, DC Booster circuit, Power
utilization monitoring circuit, thermal insulation jacket with heat transfer plates.
2. To produce TE Refrigerator in user friendly in compact seize.
3. To analyze heat transfer phenomena through fins of hot side, cold side in ANSYS
FEA and also to analyze heat insulation capability of thermal insulation jacket,
booster circuit current step up performance is to be experimented and understood.
4. To improve coefficient of performance to the greater extent and TEC should obtain
minimum ΔTCold = 100
C to the ambient, decrease the cost of fabrication with simple
and attractive design.
1.8. Organization of the Thesis
This thesis is structured in five correlated chapters in following order.
Chapter 1 provides introduction to my thesis.
Chapter 2 discusses state of the art literature review in thermoelectric refrigeration.
Chapter 3 describes methodology.
Chapter 4 interprets the as obtained results.
Chapter 5 concludes the research and presents summary of research findings.

5
CHAPTER 2
LITERATURE REVIEW
2.1. Background
Thermoelectric coolers (TEC), also known as Peltier Coolers are solid state heat pumps
that utilize the Peltier effect to move heat. The principle of thermoelectric cooling dates
back to the discovery of the Peltier effect by Jean Peltier in 1834. Peltier observed that
when electric current passes across the two junctions of two dissimilar conductors (a
thermocouple) there was a heating effect that could not be explained by Joule heating
alone. Infect, the direction of current decides the cooling effect or heating effect. This
effect can be harnessed to transfer heat, creating a heater or cooler. Peltier could not
realize the importance of this phenomenon and the other scientists also could not utilize
this phenomenon till late 20th
century. Thermoelectric technology, as one entirely solid
state energy conversion way, can directly transform thermal energy in to electricity and
vice-versa by using thermoelectric transformation materials. A thermoelectric module
has no moving parts, and is compact, quiet, highly reliable and environment friendly.
Due to these merits, this technology is presently becoming a noticeable research
direction. Bell (2008); Heremans et al. (2008); Poudel et al. (2008); Hochbaum et al.
(2008); Boukai et al. (2008); Lyeo et al. (2004); Hsu et al. (2004).
2.2. Working of TEC
When the two ends of two dissimilar conductors are connected to a battery, electrons
flow out of one in which the electrons are loosely bound to the other one in which the
electrons are tightly bound. This occurs due to the deference in the Fermi level between
the conductors. The Fermi level represents the demarcation in energy within the
conduction band of a metal, between the energy level occupied and unoccupied energy

6
levels. When the two different conductors are joined which have different Fermi levels,
electron start flowing from the conductor with higher level to the other one. This flow
continues till the electrostatic potential bridges this gap and the two Fermi levels come at
the same value. Current passing across the junction results in either a forward or a
reverse bias, resulting in temperature gradient. If the temperature of the hotter junction is
kept low by removing the heat, the temperature of the cold plate can be cooled by tens of
degrees.
2.3. Choosing materials
At first glance metals with their low electrical resistance might seem like a good choice
for TEC construction; however they also have high thermal conductivity. This tends to
work against any heat gradient produced and lowers their overall ZT (Z is figure of
merit, T is operating temperature) value. In practice semi-conductors are the material of
choice. These are usually manufactured by either directional crystallization from a melt
or pressed powder metallurgy. The thermoelectric semiconductor material most often
used for TEC is an alloy of Bismuth Telluride (Bi2Te3) that has been suitably doped to
provide individual blocks or elements having distinct “n” and “p” characteristics. Other
thermoelectric materials include Lead-Telluride (Pb-Te), Silicon-Germanium (Si-Ge)
and Bismuth-Antimony (Bi- Sb) alloys, which may be used in specific situation. There
has been considerable interest in finding new materials and structures to use in clear,
highly efficient cooling and energy conversion systems. Wood (1988); Mahan et al.
(1997). The increase in ZT = α2
T/ρk, leads directly to the improvement in the cooling
efficiency of Peltier modules and in the energy conversion efficiency of TEG.
Goldshmid (2004). Much effort has been made to raise Z of TE materials using various
methods so that there are improvements in Z ( for example, 3.2 × 10-3
K-1
at 300 K, 3.99

7
× 10-3
K-1
at 298 K, 3.70 × 10-3
K-1
at room temperature and 4.58 × 10-3
K-1
at 308 K for
Bi3-Te3 alloys.) Yim et al. (1972); Ettenberg et al. (1996); Yamshita et al. (2003).
2.4. TEC Construction
TEC are constructed using two dissimilar semi-conductors, n-type and p-type (in order to
have different electron densities needed for better effect) Fig. 2.1. The two semi-
conductors are positioned thermally in parallel and joined at one end by a conducting
cooling plate (typically of copper or aluminum). A voltage is applied to the free ends of
the two different conducting materials, resulting in a flow of electricity through the two
semi conductors in series. The flow of DC across the junction of the two semiconductors
creates a temperature difference. Giving rise to Peltier cooling and hence absorption of
heat from the vicinity of the cooling plate. If the direction of current is changed by
changing the polarity of the battery, the cold side becomes hot side and the hot side
becomes cold side in TEC.
Fig. 2.1: TEC construction.
2.5. Thermoelectric Effect
The thermoelectric effect is the direct conversion of temperature differences to electric
voltage and vice versa via a thermocouple. This effect can be used to generate electricity,
measure temperature or change the temperature of objects. In this five effects are

8
observed: Seebeck effect, Peltier effect, Thomson effect, Joulean effect and Conduction
effect.
2.5.1. Seebeck Effect
When two junctions of a pair of dissimilar metals are maintained at different
temperatures, there is a generation of emf (electromotive force). A series of tests by
varying the temperature of the junctions of various combinations of a set of materials
were conducted and it was found that
E  T------ (2.1)
Where ΔE is emf output and ΔT is temperature difference of the junctions. This
phenomenon of generation of emf is known as Seebeck effect. The proportionality
constant of Eq.(1): αab=
ΔE
ΔT
------ (2.2)
Above Eq.(2) is called Seebeck coefficient. Seebeck coefficient is the property of a
material that determines the performance ability of thermocouples. Here αab= αa- αb is the
coefficient for two different metals (A & B or p and n).
2.5.2. Peltier Effect
If the direct current is passed through a pair of dissimilar metals, there is a heating at one
junction, cooling at the other depending upon material combinations. Peltier varied the
current and observed the heating and cooling rate for different sets of elements. It was
found that: Q  I ------ (2.3)
Where Q is the cooling or heating rate. The proportionality constant for Eq. (2.3) is
called Peltier coefficient, Π i.e. Q I =  ab ------ (2.4)

9
Where  ab =  a− b is the coefficient for two different metals.
2.5.3. Thomson Effect
Thomson effect, the evolution or absorption of heat when electric current passes through
a circuit composed of a single material that has a temperature difference along its length.
This transfer of heat is superimposed on the common production of heat associated with
the electrical resistance to currents in conductors. When a current passes through a single
conductor having a temperature gradient, heat transfer is given by:
𝛿𝑄
𝛿𝑥
= 𝜏𝐼 (
𝑑𝑇
𝑑𝑥
) ------ (2.5)
Where τ being Thomson coefficient and δQ/δx is the Thomson heat transfer.
Using first and second law of thermodynamics a relation between Seebeck and Peltier
coefficient can be established as:
ab = ab T ------ (2.6)
𝜏 𝑎−𝜏 𝑏
𝑇
=
𝑑𝛼 𝑎𝑏
𝑑𝑇
------ (2.7)
Using Eq.2.4 and 2.6, it is found:
Q = ab IT ------ (2.8)
This is clear from Eq. 2.8 that to get high Q, αab should be high otherwise large current
will be required.
2.5.3. Joulean Effect
When the electrical current flows through a conductor, there is dissipation of electrical
energy. According to Joule it is related as:

10
Qj = I2
R ------ (2.9)
Where I and R are the current and electrical resistance.
2.5.5. Conduction Effect
If the ends of any element are maintained at different temperatures, there is heat transfer
from the hot end to the cold end and is related by:
Qcond = U(Th-Ti) ------ (2.10)
Where U being overall conductance and Th , Ti are high and low temperatures
respectively. If there is only one conductor of cross-sectional area A, conductivity K and
length L, the overall conductance is given by:
U =
𝑘𝐴
𝐿
------ (2.11)
2.6. Exergy
In thermodynamics, the exergy of a system is the maximum useful work possible during
a process that brings the system into equilibrium with a heat reservoir. Exergy is the
energy that is available to be converted in form of useful energy. When the system
reaches a state when it is in equilibrium with surroundings (called a dead state), the
exergy is zero. Measurement of exergy is always of primary interest in thermodynamics.
The word ‘exergy’ was first used by Zoran Rant (1904-1972) that combines two Greek
words ‘Ex’ and ‘Ergon’ which means ‘from work’ but concept was built up by J. Willard
Gibbs in 1873. Energy and exergy differ in their behavior as energy can never be created
or destroyed but exergy is destroyed during a process due to irreversibility’s and causes
entropy generation. Therefore energy has two parts, one is available called ‘exergy’ and
another which is not available called ‘anergy’. In the field of thermal engineering exergy
analysis is used as a tool to utilize energy in more efficient way. Exergy is a combined

11
property of the system as well as surroundings as it includes the state of system and
surroundings both.
Exergy is also known with similar names e.g. availability, available energy, utilizable
energy, available useful work, maximum amount of (or minimum) work, reversible
work, and ideal work. In a cycle which includes number of processes, exergy destruction
is calculated for each processes individually and then added for the entire cycle. Exergy
destruction can also be determined by determining the entropy generation.
Thermodynamic second law efficiency can be calculated with the help of exergy
destruction or entropy generation which is the more authentic efficiency in comparison
to the first law efficiency. Cengel et al. (1989).
2.7. Benefits of TEC
While refrigerators and air-conditioners utilize compressors, condensers and refrigerants
to lower temperature; solid state cooling utilizes DC power, heat sinks and
semiconductors. Venkatasubramanain et al. (2001); Chen et al. (2010); Yamashita
(2009); Yamashita (2008). This fundamental difference gives solid state thermoelectric
coolers the following advantages over conventional devices.
1. Environment friendly (as no refrigerants are used). Therefore leaking problem of
refrigerants can also be avoided. As CFC’s have high ozone depletion potential and
HCFC’s have comparatively low ozone depletion level, they are being phased out. At
this situation TEC’s can be the best alternate as it has zero harmful effect.
2. Can be manufactured in compact sizes using less space.
3. Light weight, which can be advantageous where light weight is more important
feature than COP. (e.g. in aircrafts).

12
4. Rate of refrigeration and COP can be easily controlled by varying voltage and
current.
2.8. State of Art Review
It is as follows:
2.8.1. Performance Investigation
The novel concept of thermoelectric self cooling introduced as a cooling and temperature
control of a device using thermoelectric technology without electricity consumption was
studied by Martínez et al., 2011. Various theoretical and experimental studies have been
reported to evaluate and enhance the utility of thermoelectric coolers. The performance
of a thermoelectric air cooling module for electronic device was studied by Chang et al.,
2009. It was shown that at a specific heat load, the thermoelectric cooling module
reaches the best cooling performance at an optimum input current. An experimental
investigation using a Peltier thermoelectric cooler to cool down a cryo probe for
cryosurgery was performed by Putra et al., 2010. Two prototypes of cryosurgery devices
consisting of 5 to 6 stages of TEC modules were analyzed using a variety of electrical
voltages. A model of thermoelectric generator driven thermoelectric refrigerator with
external heat transfer was probed. The influence of the external and internal
irreversibilities of the thermoelectric refrigeration device on the performance of the
system was analyzed (Chen et al., 2011, Pan et al., 2007).
2.8.2. Power for TEC
Commercially available solid-state thermoelectric devices may be used for their
electrical power generation capabilities when coupled to a thermometric refrigerator or
heat pump. The DC current provided to run a thermoelectric refrigerator can be
generated from batteries or solar cells also. Many researchers have done experimental

13
investigation of a TEC coupled with a solar cell. A solar- driven thermoelectric cooling
module with a waste heat refrigeration unit designed for green building application was
investigated (Dai et al., 2003, Cheng et al., 2011). It was found that the approach was
able to produce a 16.2 O
C temperature difference. Thermoelectric coolers were found
suitable for such applications where a precise control of temperature is required. An
analysis of TEC performance was conducted for high power electronic packages such as
processors. The cooling capacity, junction temperature, COP of TEC and the required
heat sink thermal resistance at the TEC hot side were computed. Design and testing of a
microprocessor controlled portable thermoelectric medical cooling kit was done (Zhang
et al., 2010, Güler and Ahiska, 2002, Chein and Huang, 2004).
2.8.3. TEC as a Hybrid System
Hybrid systems like thermoelectric system and vapor compression systems have also
been tried by Vián and Astrain, 2009. Riffat and Guaquan, 2004. The performance of
three types of domestic air conditioners namely the vapor compression air conditioner
(VCACs), the vapor absorption air conditioner(VAACs) and the thermoelectric air-
conditioner (TEACs) was compared. The comparison showed that although VCACs have
the advantages of high COP and low purchase price, use of these systems will be phased
out due to their contribution to the green house effect and depletion of ozone. VAACs
are generally bulky, complex and expensive but operate on thermal energy so their
operational cost is low. TEACs are environment friendly, simple and reliable but are still
expensive. Their low COP is an additional factor. TEACs however, have a large
potential market as air-conditioner of small enclosures such as cars and submarine
cabins. In recent years much researchers have done more work in thermoelectric cooling.
(Min et al., 1999; Khedari et al., 2001; Chen et al., 1996).

14
2.8.4. Optimization of TEC
To obtain an optimized performance from thermoelectric cooler various optimization
techniques have been used to optimize the operational performance as well as their size.
A general approach in evaluating and optimizing thermoelectric cooler performance was
presented by Zhang in 2010. A numerical study on the performance of miniature
thermoelectric cooler affected by Thomson effect was done (Chen et al., 2012, Du and
Wen, 2011). With the help of optimal control theory, development of a sufficiently
precise technique for computerized design of segmented thermoelectric coolers was done
(Vikhor and Anatychuk, 2006). Pérez–Aparicio et al., 2012 did a finite element
simulation of a commercial thermoelectric cell, working as a cooling heat pump. This
analysis concludes that the temperature dependence of the materials properties of electric
conductivity and Seebeck coefficient is very relevant on cell performance. Cooling
capacities, coefficient of performance as well as the dimension of legs, leg area and
number of legs of TEC were optimized using genetic algorithm (Cheng and Shih, 2006,
Cheng and Lin, 2005). A model which was different from the other studies, in which the
p-n pair was simply treated as a single bulk material was developed. In this model the
thermoelectric cooler was divided into four major regions, namely, cold end, hot end, p
type and n type thermoelectric element (Cheng et al., 2010). A new study in which
Z,K,and R etc. parameters of standard TE module of Melcor Inc. had been acquired with
a new computer controlled system, Thermoelectric Performance Analysis System
(TEPAS) by Ahiska et al., 2012. A temperature –entropy analysis was done, where the
Thomson effect bridges the Joule heat and Fourier heat across the thermoelectric
elements of a thermoelectric cooling cycle to describe the potential energy flows or
performance bottlenecks or dissipations (Chakraborty et al., 2006). A generalized
theoretical model was presented for the optimization of a thermoelectric cooling system

15
in which the thermal conductance’s from the hot and cold sides of the system were taken
in to account by Zhou and Yu, 2011. A detailed analysis of the optimal allocation of the
finite thermal conductance between the hot side and cold side heat exchangers of the
TEC systems were conducted considering the constraint of the total thermal
conductance. The analysis showed that the maximum COP and the maximum cooling
capacity of the TEC system can be obtained when the finite total thermal conductance is
optimally allocated. Luo et al., 2003 applied the theory of finite time thermodynamics to
analyze and optimize the performance of a thermoelectric refrigerator, which is
composed of multiple elements. In general, conventional non-equilibrium
thermodynamics is used to analyze the performance of single stage one or multiple
element thermoelectric generators. Susman et al. (1995); Chen et al. (1996); Chen et al.
(1997); Rowe et al. (1998); Omer et al. (1998); Mayergoyz et al. (1001); Naji et al.
(2003); Nuwayhid et al. (2005); Chen et al. (2007); YU et al. (2007). The theory of finite
time thermodyanamics or entropy generation minimization is also a powerful tool for the
performance analysis and optimization of practical thermodynamic process and devices.
Andresen (1983); Andresen et al. (1984); Sieniutycz et al. (1990); Devos (1992);
Sieniutycz et al. (1994); Bejan (1996); Hoffmann et al. (1997); Beery et al. (1999); Chen
et al. (1999); Gordon (2000); Chen et al. (2004). Some authors have investigated the
performance of thermoelectric generators and coolers using of finite time
thermodynamics as well as non-equilibrium thermodynamics. Sun et al,. (1990); Sun et
al. (1993); Gordon (1991); Wu (1993); Wu (1993&1996); Agarwal et al. (1997); Chen at
al. (1996, 1997 & 2000); Xuan et al. (2002) and Nuwayhid et al. (2003) analyzed the
effect of finite rate heat transfer between the thermoelectric device and its external heat
reservoirs on the performance of single-element single stage thermoelectric generators.
Chen et al. (2000, 2002 & 2004) and Crane et al. (2004) investigated the characteristics

16
of single stage thermoelectric generators which has number of elements with the
irreversibility due to finite rate heat transfer. Effect of Joulean heat inside the
thermoelectric device and the heat leak through the thermometric couple element was
also considered.
2.8.5. Single-stage and Multi-stage TEC
Thermoelectric coolers can work in single stage as well as in multistage configurations.
A multistage thermoelectric device should be used only when a single stage device is not
able satisfy temperature control requirements. Fig 2.2 shows two graphs: the first plot
gives the variation of temperature difference vs. normalized power input of single and
multistage devices. The second plot gives the variation of ΔT vs. COP. These figures
should help one to identify when to consider cascades since they portray the effective ΔT
range of the various stages.
Fig. 2.2: Behaviour of single and multistage TEC’s.

17
A two-stage cascade should be considered somewhere between a ΔT of 40°C and 65°C.
Below a ΔT of 40°C, a single stage module may be used, and a ΔT above 65°C may
require a 3, 4 or even 5 stage modules. A theoretical analysis and simulating calculations
were conducted for a basic two-stage thermoelectric module, which contains one
thermocouple in second stage and several thermocouples in the first stage. A pyramid-
type multistage cooler was analyzed, focusing on the importance of maximum attainable
target heat flux and over all coefficient of performance (Yu et al., 2007, Yu and Wang,
2009, Karimi et al., 2011).
2.8.6. Feasibility Study of TEC
Various three dimensional models studies and experimental investigations have been
done to evaluate the feasibility of thermoelectric coolers. An experimental study was
done to produce a portable solar still. The technique consists of using a solar collector, a
wall covered with black wool and water, sprinkling system to increase evaporation rate
and a thermoelectric cooling device to enhance water condensation (Esfahani et al.,
2011). The feasibility study of using thermometric coolers in a dehumidification system
to condense atmospheric moisture and generate renewable fresh water was done by
Milan et al., 2011. A refrigerator system of thermoelectric refrigerator (TER; 25x25x35
cm2) was fabricated by Jugsujinda et al., 2011 using a thermoelectric cooler (TEC; 4x4
cm2). Numerical analysis has been carried out to figure out the performance of the
thermoelectric micro-cooler with the three dimensional design by Lee et al., 2007. A heat
exchanger for the cold side of a Peltier pellets in thermoelectric refrigeration, based on
the principle of a thermosyphon with phase change and capillary action was developed
(Vian and Astrain, 2008, Slaton and Zeegars, 2006, Chen et al., 2002). It was found that
the COP of the thermoelectric refrigerator can be improved up to 32% by incorporating
the developed device. A model of thermoelectric generator driven thermoelectric

18
refrigerator with external heat transfer was proposed. The performance of the combined
thermoelectric refrigerator device obeying Newton’s heat transfer law was analyzed
using the combination of finite time thermodynamics and non-equilibrium
thermodynamics. Chen et al (2012). An experimental investigation was carried out to
characterize the performance of thermoelectric modules used for electric power
generation over a range of different resistance loads. The performance of a Peltier cell
used as a thermoelectric generator was evaluated in terms of power output and
conversion efficiency. The results showed that a thermoelectric module is a promising
device for waste heat recovery. Casano et al (2011). A study was done to investigate the
performance of a TEG combined with an air-cooling system designed using two-stage
optimization. An analytical method was used to model the heat transfer of the heat sink
and a numerical method with a finite element scheme was employed to predict the
performance of the TEG. WangChien et al (2012). A concept of thermoelectric
cogeneration system (‘TCS’) was proposed to highlight the direction for enhancing the
sustainability by improving the energy efficiency in domestic sector. In comparision to
the thermoelectric systems used in the areas where the part of converted energy is being
used and unconverted part is discharged to the environment, a system was developed
which recovers the available part of energy by producing electrical power and hot water
from unavailable part. Therefore it utilizes the energy completely without wastage.
Zheng et al (2013). Recently there is an increasing interest in the use of TEC for
enhanced cooling of high power components like microprocessors in both manufacturing
test process and user conditions. High cooling capacity TECs, in combination of air
cooling or liquid cooling techniques, were persuaded to extend the conventional air
cooling limits for high power dissipating microprocessors (Bierschenk et al., 2004;
Bierschenk et al., 2006; Chen et al., 2004; Hasan et al., 2007; Pehlan et al., 2002).

19
2.9. Thermo Economics
Thermoeconomics, as an exergy-aided cost reduction method, provides important
information for the design of cost effective energy conversion systems. The exergy
costing principle is used to assign monitory values to all material and energy streams
within a system as well as the exergy destruction within the system. The design
evaluation and optimization is based upon the trade-off between exergy destruction
(exegetic efficiency) and investment cost. It is observed that in most of the studies
(Adnan, 2001; Aprea et al, 2002; Adnan et al., 2003; Aprea et al., 2004; Adnan et al.,
2007; Kabul et al;, 2008; Ozkaymak et al., 2008; bayrakci et al., 2009; Kizilkan et al.,
2010; Variyelni et al., 2011), performance comparison and performance analysis of
refrigeration system is performed using energy approach based on first law and exergy
analysis based on second law. Energy and exergy approaches are generally well known
approaches, used to analyze thermal processes. Researchers who are working rigorously
in the design of energy transformation plants and are willing to improve the first in hand
design are keen to find out the answers of following questions:
1. What are the basic causes of thermodynamic inefficiencies in the system and how
significant are they?
2. What measures should be taken or what may the alternative changes in the designs
that would improve the efficiency of the overall plant?
3. How much is the total required investment and the total equipment cost of the plant?
4. How much do the thermodynamic inefficiencies cost the plant operator?
5. How to decrease plant operating & maintenance cost?
6. What measures should be taken to improve the cost effectiveness of the overall
plant?

20
The answer to the first questions is provided with the aid of an energy and exergy
analysis. An economic analysis answers the third question. The last two questions can be
answered with the aid of a thermo economic analysis. This analysis is called exergo
economics, which is a more precise characterization of every exergy-aided cost reduction
approach. A detailed study of thermo economics is found in Bejan et al. (1996); El-
Sayed (2003). Exego economics applied to the design optimization represents a unique
combination of exergy analysis and cost analysis, to provide the designer of an energy
conversion plant with information not available through conventional energy, exergy or
cost analysis, but crucial to the design of cost effective plant. Design optimization of
energy conversion system means the selection of structure and the design parameters (the
design variables) of the system to minimize the total cost of the system products (over
the entire lifetime of the system) under boundary conditions associated with available
materials, financial resources, environmental protection and government regulation as
well as the safety, reliability, operability, maintainability and availability of the system.
A thermodynamic optimization, which aims at minimizing the thermodynamic
inefficiencies, represents a sub case of the general case of design optimization. An
appropriate formulation of the optimization problem is always one of the most important
and sometimes the most difficult task in the optimization study. There are various
terminologies and names given to various exergo economic approaches presented in the
past by researchers in previous years.
These names include the following:
• Exergy Economic Approach (EEA)
• First Exergo economic Approach (FEA)
• Thermo economic Functional Analysis (TEA)
• Exergetic Cost Theory (ECT)

21
• Engineering Functional analysis (EFA)
• Last-in-First Out Approach (LIFOA)
• Structural Analysis Approach (SAA)
• SPECO Method (SPECOM)
2.10. Recent Developments in Thermo Electrics
A computational model was developed by Martínez et al. (2013) for thermoelectric self-
cooling applications, capable of simulating both the steady and the transient state of the
whole system. This system was supported by fluid dynamics software and was based on
implicit finite differences. This model was able to solve the system equations which
involved Fourier’s law, thermoelectric effects Seebeck, Peltier, Joule and Thomson and
the properties which are dependent on temperature difference. This model also has the
capability to handle the new analytical expressions and functions to simulate any other
component of the system which is more precision or has more complex design. Ming &
Jianlin (2013) presented a comprehensive analysis of a novel two-stage cascade
thermoelectric cooler (TTEC). The novel TTEC was formed by joining short-legged
thermoelectric couples in cascade, which had advantages of no inter stage electrical
insulating materials, compact and easy-fabricated structure, and used only one operating
power. An analytical model taking into account the allocation of the total input current
between the two stages of the TTEC was developed and the performance characteristics
were investigated in detail.
Lin et al. (2013) studied on the optimal heat exchanger configuration of a TEC system.
The effects of total heat transfer area allocation ratio, thermal conductance of the TEC
hot and cold side and TEM element material properties on the cooling performance of
the TEC were investigated in detailed based on the developed mathematical model. The

22
analysis results indicate that the highest coefficient of performance (COP), highest heat
flux pumping capability of the TEC and lowest cold side temperature can be achieved by
selecting an optimal heat transfer area allocation ratio. Huang et al. (2013) developed an
inverse problem approach to optimize the geometric structure of TECs (thermoelectric
coolers).
Teaching–learning-based optimization (TLBO) is a recently developed heuristic
algorithm based on the natural phenomenon of teaching–learning process. In the present
work, a modified version of the TLBO algorithm was introduced by Rao & Patel (2013)
and applied for the multi-objective optimization of a two stage thermoelectric cooler
(TEC).
Temperature increment is one of the main challenges for solar concentrating photovoltaic
systems which causes significant reduction in the cell efficiency and accelerates cell
degradation. To overcome this issue, a novel cooling method by using Peltier effect was
proposed and investigated by Najafi & Woodbury (2013). In this approach, a
thermoelectric cooling module was considered to be attached to the back side of a single
photovoltaic cell. A detailed model was developed and simulated via MATLAB in order
to determine the temperatures within the system, calculate the required power to run the
thermoelectric cooling module was calculated and the extra generated power by
photovoltaic cells due to the cooling effect was done.
A theoretical investigation to optimize thermoelectric cooling modules was performed
using a novel one dimensional analytic model by Jeong (2014). In the model the
optimum current, which maximizes the COP of a thermoelectric cooling module, was
determined by the cooling capacity of a thermo element, the hot and cold side
temperatures, the thermal and electrical contact resistances and the properties of

23
thermoelectric material, but not by the length of a thermo element. The application of a
TEG (thermoelectric power generator) to harvest energy from the waste heat of a
commercial table lamp was investigated experimentally as well as numerically by Weng
& Huang (2014). The table lamp was integrated with TEG chips which were cooled by a
natural convection heat sink. Possible use of a novel portable desalination system was
investigated experimentally by Yildirim et al. (2014). The system was based on
humidification–dehumidification principle and thermoelectric cooling technique. A
thermoelectric cooler was combined into the system to increase humidification and
dehumidification processes.
Theoretical and experimental investigations of the winter operation mode of a
thermoelectric cooling and heating system driven by a heat pipe photovoltaic/thermal
(PV/T) panel was done by He et al. (2014) . And the energy and exergy analysis of this
system in summer and winter operation modes were also done. A feasibility study was
performed by Suh et al. (2014) applying a thermoelectric device to the energy storage
system of an electric vehicle. A thermoelectric module was used for a lithium family
battery system for controlling the cooling and preheating of the battery and to recover the
energy which is being wasted.
Geometric design of an integrated thermoelectric generation-cooling system was
performed numerically by Chen et al. (2014) using a finite element method. In the
system, a thermoelectric cooler (TEC) was powered directly by a thermoelectric
generator (TEG). Two different boundary conditions in association with the effects of
contact resistance and heat convection on system performance were taken into account.
A multi-objective and multi-parameter optimization was implemented by Meng et al.
(2014) to design the optimal structure of bismuth-telluride-based TEG (thermoelectric

24
generator) module. A multi-physics TEG model combining the SCG (simplified
conjugate-gradient) algorithm was used as the optimization tool. A thermoelectric
generator must be designed keeping all geometric features in to account to enhance the
performance such as efficiency and power output. A study has been done in which three
the-state-of-the-art multi-objective evolutionary algorithms, namely, NSGA-II (Non-
dominated Sorting Genetic Algorithm-II), GDE3 (Generalized Differential Evolution
generation 3), and SMPSO (Speedconstrained Multi-objective Particle Swarm
Optimization) are used to optimize the geometric features of a thermoelectric generator
to improve its efficiency and power output when it is operating in different conditions.
Geometric parameters may be defined shape factor and size of pin length and the
operating parameters may be defined as temperature ratio and load on thermoelectric
cooler. A thermal investigation has been done by taking the geometric and operating
features in to account. The findings were also validated with a practical system. It was
reported in the literature that pin size and shape factor both have noticeable impact on the
performance of the device. If the shape factor in increased, it initially increases the
thermal efficiency up to a maximum value but the further increase in shape factor
deteriorates the thermal efficiency. The power output from the module behaves
differently. It increases initially with the increment in the shape factor but then no effect
is registered in power out with further increment of shape factor. A new designed was
presented for a specific operating conditions for a thermoelectric power generation
module to give maximum thermal efficiency and power output. Ibrahim et al. (2014). An
ideal heat exchanger should recover as much heat as possible from an engine exhaust at
the cost of an appreciable pressure drop. The primary heat is provided to thermoelectric
generator (TEG), and their capacity and efficiency is dependent on the physical
properties of the element like material, shape, and type of the heat exchanger. Six

25
different exhaust heat exchangers were investigated within the same shell, and their
computational fluid dynamics (CFD) models were developed to compare heat transfer
and pressure drop in typical driving cycles for a vehicle with a petrol engine. The result
showed that the serial plate structure enhanced heat transfer with the help of baffles and
the rate of heat transfer was maximum. It also produced a significant pressure drop of in
a suburban driving cycle. The numerical results for the pipe structure and an empty
cavity were also validated with the help an experiment setup. Bai et al., 2014. A study
has been done by combining thermionic-thermoelectric refrigerator which has a finite
rate heat transfer. In this study expressions were derived for rate of heat transfer and
coefficient of performance, the most important parameters for a refrigeration system. The
performance of the irreversible combined refrigerator, in which the heat transfer between
the device and the heat reservoir obeys Newton's heat transfer law, was analyzed and
optimized by using the combination of finite time thermodynamics and non-equilibrium
thermodynamics. The impact of external heat transfer was reported by comparing the
behavior of irreversible combined refrigerator with the conventional analysis without
heat transfer losses. The behavior of the combined refrigerator device with external heat
transfer was further compared with those of an independent vacuum thermionic
refrigerator with and without considering external heat transfer. Moreover, for the fixed
total heat transfer surface area of four heat exchangers, the allocations of the heat transfer
surface area among the four heat exchangers are investigated for maximizing the cooling
load and the COP. The effect of total heat transfer surface area on the optimum
performance of the irreversible refrigerator was explored with the help of numerical
analysis of modules. The results obtained are helpful to provide guidelines for the design
and application of practical combined thermo-ionic and thermoelectric refrigeration
devices. Ding et al (2014).

26
A study was reported with three-dimensional multi-physics model to optimize the
performance of three kinds of multi-stage thermoelectric coolers, connected electrically
in series, in parallel, and separated, respectively. The optimizations were performed for
the two-stage thermoelectric coolers with number of thermoelectric elements. The
number ratio and current ratio were investigated to reach the optimal rate of
refrigeration, coefficient of performance, and maximum temperature difference,
respectively. A significant temperature distribution was observed for the two-stage
thermoelectric cooler with number ratio larger or smaller 1.00. In addition, the properties
which are dependent on temperature were proven to be extremely important for
predicting the two-stage thermoelectric cooler performance. Thermal resistance models
extensively adopted in the previous two stage thermoelectric cooler studies could not
predict the two-stage thermoelectric cooler performance accurately because they assume
the one-dimensional temperature distribution and constant material properties. The
results also show that the thermoelectric element number on the hot stage should be
larger than that on the cold stage for improving the cooling capacity and COP. It was
also reported that the performance can be improved by applying the different amount of
current in two stages. Wang et al. (2014) a theoretical model was developed for
evaluating the efficiency of concentrating photovoltaic thermoelectric hybrid system.
Hybrid systems with different photovoltaic cells was studied, that includes crystalline
silicon photovoltaic cell, silicon thin-film photovoltaic cell, polymer photovoltaic cell
and copper indium gallium selenide photovoltaic cell. The effect of temperature on the
efficiency of photovoltaic cell was taken into account based on the semiconductor
expressions, which showed different efficiency temperature behavior of polymer
photovoltaic cells. It was demonstrated that the polycrystalline silicon thin-film
photovoltaic cell is suitable for concentrating photovoltaic thermoelectric hybrid system.

27
With the help of optimization of the convection heat transfer coefficient and
concentrating ratio, the polymer photovoltaic cell is proved to be suitable for non-
concentrating photovoltaic thermoelectric hybrid system. Zhang et al. (2014). A
combined thermal system consisting of a thermoelectric generator and a refrigerator was
considered and the effect of location of the thermoelectric generator, in the refrigeration
cycle, on the performance characteristics of the combined system was investigated. The
operating conditions and their influence on coefficient of performance of the combined
system were examined through introducing the dimensionless parameters, such as k(k =
QHTE/QH, where QHTE is heat transfer to the thermoelectric generator from the condenser,
QH is the total heat transfer from the condenser to its ambient), temperature ratio (hL = TL/
TH, where TL is the evaporator temperature and TH is the condenser temperature), rC (rC =
CL/CH, where CL is the thermal capacitance due to heat transfer to evaporator and CH, is
the thermal capacitance due to heat rejected from the condenser), hw (hw = TW/TH, where
TW is the ambient temperature), hC (hC = TC / TH, where TC is the cold space temperature).
It was found that the location of the thermoelectric generator in between the condenser
and the evaporator decreases coefficient of performance of the combined system.
Alternatively, the location of thermoelectric device in between the condenser and its
ambient enhances coefficient of performance of the combined system. The operating
parameter has significant effect on the performance characteristics of the combined
system. Bekir et al. (2014).
Three different methods for predicting the Seebeck coefficient and power generation of a
commercial available thermoelectric cooler module were used and compared to the
experimental data. First method and second method were developed based on
mathematical models and third method was established in terms of experimental
measurements. Method 3 considers the effect of cooling condition, whereas Method 1

28
and 2 did not. Two different temperatures at the cold side of the thermoelectric cooler
module were also considered to account for the influence of cooling condition on the
performance of the thermoelectric cooler. The power generation of the thermoelectric
cooler module with low-temperature cooling is at least 5% higher than that with normal
cooling. Method 3 gives the best prediction in open circuit voltage and power generation.
Basically, the three methods are able to evaluate the properties and performance of a
TEC easily, thereby providing useful tools for designing and constructing a TE
generation system. Chen et al. (2015).
Energy crisis and environment deterioration are two major problems for 21st
century.
Thermoelectric device is a promising solution for those two problems. This review
begins with the basic concepts of the thermoelectric and discusses its recent material
researches about the figure of merit. It also reports the recent applications of the
thermoelectric generator, including the structure optimization which significantly affects
the thermoelectric generator, the low temperature recovery, the heat resource and its
application area. Then it reports the recent application of the thermoelectric cooler
including the thermoelectric model and its application area. It ends with the discussion of
the further research direction. Wei et al. (2015).
A study was presented to a comprehensive thermodynamic modeling of a novel portable
solar still through the first and second laws (of thermodynamics) analysis. In the new
solar still, a thermoelectric module was employed to increase the temperature difference
between evaporating and condensing zones. Energy and exergy balance equations were
written for all components of the solar still including glass cover, thermoelectric module,
saline water, and basin-liner. A new approach has been used to evaluate evaporative heat
transfer coefficients. Comparison of distilled water calculated by the present approach

29
and the results obtained by employing various semi-experimental models proved the
accuracy of the proposed thermodynamic modeling. It was also found that the exergy
stored within the body of saline water, which was neglected in the most previous studies,
is important and should be considered. It was shown that the daily average energy and
exergy efficiencies of the solar still are around 20% and 1%, respectively. It was also
reported that the exergy efficiency is much lower than the energy efficiency. It was
observed that the rate of exergy destructions in solar still components is proportional to
the incident solar intensity. The largest exergy destruction belongs to the thermoelectric
module, which is 64% of the total exergy destruction, while the glass cover has the
smallest share. It is concluded that although the energy efficiency associated with this
type of thermoelectrically assisted solar still is higher than it’s the other options like
simple passive solar still one, however, its exergy efficiency is lower. Dehghan et al.
(2015).
2.11. Gaps and Opportunities
1. Second Law Analysis of thermoelectric devices is required to understand their
potential to serve the desired purposes.
2. Optimized operating condition should be evaluated to improve the performance.
3. Optimized design should be developed to enhance the application of thermoelectric
devices where size, weight and shape are more important than efficiency or COP.

30
CHAPTER 3
MATERIAL AND METHODOLOGY
This experiment is carried out in following three stages:
Stage 1: Prepare Peltier thermo elements CAD model and perform FEA thermo electric
steady state heat analysis.
Stage 2: Prepare heat sink CAD model and perform FEA steady state and forced
convection heat analysis. Design and experiment cooling fan with electronic power
monitoring system for heat sink cooling.
Stage 3: Prepare TEC CAD and practical model with thermal insulation jacket; perform
FEA steady state heat analysis on water bottle with different materials to optimise
performance. Also design and fabricate DC boost converter circuit and test it with TEC.
3.1. FEM of TE Element’s:
3.1.1. Preparation of the TE CAD Model
Design of TE elements was done in ANSYS 2019 R3 as shown in Figure 3.1 CAD
model of TE module thermocouple elements which consisting of P-type and N-type legs
with attached copper base plate at top and bottom for electric conduction which
composed with 2 ceramic substrates as a foundation for electrical insulation of p-type
and n-type bismuth telluride thermo elements that connected in series and thermally in
parallel between the ceramics. Usually thermoelectric module have dimensions from 40
x 40mm square by 3.9mm thick to 60 x 60 mm square by 5mm thick and maximum heat-
pumping rate between 1 to 125W and contain from 3 to 127 thermocouples. In this paper
I considered two thermocouples of 4 elements in Peltier module and thermo electric

31
steady state heat analysis was carried out on TE module thermo elements to know the
heat flux and temperature gradient, current density and its direction by inducing different
voltages to P and N junction thermocouple legs.
Fig. 3.1: 2D and 3D model of Peltier module TE couples.
3.1.2. Geometry
2D front view and isometric 3D views of TE elements are shown in above figure 3.1
respectively. Ceramic plates of seize AL= 3.5 × 3.5mm, thickness At = 0.80mm, P and N
legs height Sh = 2.5mm and thickness St = 1.5mm, distance between legs SL = 0.50mm
also copper base plates length CL = 2.5mm and thickness Ct = 0.20mm for every
semiconductors base before ceramic plate it is insulated by thin Teflon material (thermal
conductivity is negligible in this project).

32
3.1.3. Material for Peltier Module
The most commonly used material for semiconductor electronics cooling applications is
Bi2Te3 because of its relatively high figure of merit.
A plot of various p-type semiconductor figure of merit ZT vs. temperature is shown;
within the temperature ranges concerned in cooling little appliances at (0-200O
C) Bi2Te3
performs the best
Fig. 3.2: ZT for P-type thermoelectric materials.
Similar results are shown for n-type semiconductors
Fig. 3.3: ZT for N-type thermoelectric material.
Conducting metals are used to sandwich the semiconductor because the TE performance
is also dependent on these materials, an optimal material must be chosen while TE

33
design, usually copper alloy. Also copper alloy is used as conductor plate and connecting
base for semiconductor P and N legs to form a couple by soldering, ceramic alloy plates
were used as cover insulation plates, silicon compound is used as thermal paste at joints.
Table 3.1: TEC Module Material Properties
Material
Isontropic thermal
conductivity (Wm-1
K-1
)
Isontropic
resistivity (ohm m)
Isontropic
seeback
coefficient (VK-1
)
Ceramic (Al2O3) 27 1.822E-07 0.000187
Copper Alloy 401 1.548E-08 -
P Type 1.46 1.64E-05 0.000187
N Type 1.46 1.64E-05 -0.000187
3.1.4. Meshing and Simulation
The TE model is imported from the work bench design modeler and meshed with the
mechanical APDL (ANSYS Parametric Design Language) solver is used. TE module is
meshed of four node three dimensional square element (0.2mm element seize), meshed
model of the TE module is as shown in the below Fig. 3.4, Bounding box diagonal is
14.098mm, Average surface area is 3.0711mm2
, Minimum edge length is 5.9544e-
002mm, Total number of nodes: 16160 and Elements: 2733.
Fig. 3.4: Meshing TE module model.

34
3.1.5. Applying Boundary Conditions
As shown in below figure 3.5 following are loaded boundary conditions:
1. Node (a) reflects the hot junction boundary condition of 110 0
C.
2. Node (b) reflects the cold junction boundary condition of -2 0
C.
3. Node (c) reflects the high potential boundary condition of 20 mV.
Note: Each couple takes 10 mV in this paper I considered 2 couples (20 mV). In
practical module there will be 127 couples (i.e., 127 × 20 = 12.7V)
4. Node (d) reflects the low potential boundary condition of 0 mV.
5. Node (e) reflects the convection boundary condition of 220
C ambient temperature,
Film coefficient of 5.e-006 W/mm2
.0
C.
Fig. 3.5: Loading boundary condition for TE elements.
3.1.6. Solution
3.1.6.1. Temperature Distribution
Temperature distribution of orientation to Y-axis obtained with maximum of 110.1 0
C
and minimum of -2.0013 0
C, average 56.82 0
C from the simulated result as shown in
Fig.3.6.

35
Fig. 3.6: Temperature distribution in TE element.
3.1.6.2. Heat Flux Distribution
Heat flux distribution of orientation to Y-axis obtained with maximum of 0.17772
W/mm² and minimum of 1.0245e-004 W/mm², average is 6.3537e-002 W/mm² from the
simulated result as shown in Fig. 3.7.
Fig. 3.7: Total heat flux distribution of TE element.
3.1.6.3. Total Current Density and Direction
As shown in fig 3.8 maximum current density is 4999.1mA/mm2
and minimum current
density is 0.96101 mA/mm2
, average is 563.98 mA/mm² and current passes from N Leg
to P Leg as simulated result.

36
Fig. 3.8: Total current density and direction.
3.1.6.4. Total Electric Field Intensity and Direction
As shown in Fig. 3.9 a) maximum electric field intensity is 0.8931 mV/mm and
minimum electric field intensity is 5.9601e-004 mV/mm, average electric field intensity
is 0.16694 mV/mm. b) maximum directional electric field intensity is 0.21086 mV/mm,
minimum directional electric field intensity is -0.22507 mV/mm, average directional
electric field intensity is -2.9397e-005 mV/mm as shown in below simulated Fig. 3.9
(result).
Fig. 3.9: Total electric field intensity and directional electric field intensity.

37
3.1.6.5. Joule Heat
As shown in below Fig. 3.10 Max. joule heat is 6.7133e-003 W/mm³ and Min. joule heat
is 1.268e-008 W/mm³, Average joule heat is 2.4405e-003 W/mm³.
Fig. 3.10: Joule heat.
3.2. TEC Theoretical Calculations:
This case study consists of the evaluation and calculation of performance parameters of
case namely: Calculation of performance characteristics of single stage thermoelectric
module (TEC1-12715).
3.2.1. Analysis of Thermoelectric Cooling
In a TEC, energy may be transferred from the thermoelectric system by three basic
modes: conduction, convection, and radiation. Comparison and evaluation of various
refrigeration systems requires a parameter which is applicable for all refrigerating
machines. The performance of cooling machines is therefore expressed in terms of a
non-dimensionless parameter called the Coefficient of Performance (C.O.P.) which is
expressed as the ratio of useful effect to work input.
3.2.2. Coefficient of Performance (COP)

38
In a thermocouple, when a current is passed through the circuit, five thermoelectric
effects occur. Because of the Peltier Effect, the cold plate will be cooled and the warm
plate will be heated. Heat will flow from the warm plate to the cold plate by Conduction.
Heat will be generated in each conductor and at each junction because of the Joulean
Effect and part of the Joulean heat will flow to each junction. It is usual to assume that
one half of the Joulean heat is transferred to each junction. Thomson Effect and Seebeck
Effect also occur. The net Thomson coefficient (τp - τn) becomes zero if (αp - αn) is
considered constant. Therefore we neglect the Thomson Effect and use mean
thermoelectric power which gives results equivalent to those obtained when the
Thomson Effect is included. We also assume that heat absorption and heat rejection
occurs only at the junctions and that all material property values are constants. Under
steady state conditions, we may write the following equations for the system shown
above-
Q1 = (αp - αn) T1I - U (T2 - T1) - ½ I2
R ------ (3.1)
Q2 = (αp - αn) T2I - U (T2 – T1) + ½ I2
R ------ (3.2)
Where,
(αp - αn) is the mean thermoelectric power or Seebeck coefficient in the
temperature range T1 to T2 , U is the effective thermal conductance between the two
junctions, and R is the total electrical resistance (conductors + contact resistance at
junctions). From Eq. (3.1)
T1 - T2 =
(αp − αn)T1I−(
1
2
)I2R−Q1
U
------ (3.3)
The Power input by the battery W must compensate for the power loss of the Joulean
Effect and counteract the generation of Power by the Seebeck Effect. Thus,
W = (αp - αn) (T2 – T1) I + I2
R ------ (3.4)

39
The Coefficient of Performance of the system as a refrigerating device is defined as-
C.O.P. = Q1 / W ------ (3.5)
Therefore,
C.O.P =
(αp − αn)T1I − U (T2 − T1)–( ½) I2R
(αp − αn) (T2 − T1) I + I2R
------ (3.6)
Where Q1 is the rate of refrigeration (W) obtained at temperature Tl, W is the power
input by the battery and U is the effective thermal conductance between the two
junctions. From the above expression it can be easily shown that in the absence of the
two irreversible effects, i.e., conduction effect and Joulean effect, the COP of an ideal
thermoelectric refrigeration system is same as that of a Carnot refrigerator. The
temperature difference between the junctions will be Maximum when the refrigeration
effect is zero.
An optimum current can be obtained by maximizing each of the above performance
parameters, i.e., temperature difference, refrigeration effect and COP. For example,
differentiating the expression for C.O.P with respect to “I” and equating it zero, we get
the expressions for optimum current and maximum COP as:
Iopt =
(αp − αn) (T2 − T1)
R(√1+ZTm−1)
------ (3.7)
C.O.Pmax =
(
T1
T2 − T1
) (√1+ZTm−
T1
T2
)
√1+ZTm+1
------ (3.8)
Where Z is a property parameter called figure of merit and Tm is the mean of T2 and T1.
The figure of merit Z is given by:
Z =
(αp − αn)2
UR
------ (3.9)

40
And Tm=
(T2 +T1)
2
------ (3.10)
3.2.3. Load Calculations
Single stage thermoelectric devices are capable of producing a "no load" temperature
differential of approximately 67°C. To select the thermoelectric(s) that will satisfy the
particular set of requirements three specific system parameters must be determined.
These are:
TC - Cold Surface Temperature
TH - Hot Surface Temperature
QC - The amount of heat to be absorbed at the Cold Surface of the T.E
CASE A: If the object to be cooled is in direct contact with the cold surface of the
thermoelectric, the desired temperature of the object can be considered the temperature
of the cold surface of the TE (TC).
CASE B: In situations where the object to be cooled is not in intimate contact with the
cold surface of the TE, such as volume cooling where a heat exchanger is required on the
cold surface of the TE, the cold surface of the TE (TC) may need to be several degrees
colder than the ultimate desired object temperature.
The Hot surface may be determined by two major parameters:
1. The temperature of the ambient environment (32O
C) to which the heat is being
rejected.
2. The efficiency of the heat exchanger that is between the hot surface of the TE and the
ambient.
The heat sink is a key component in the assembly. The thermal resistances of the heat
sink causes a temperature rise above ambient. If the thermal resistance of the heat sink is
unknown, then estimates of acceptable temperature rise above ambient are:

41
Table 3.2: Acceptable temperatures
Natural Convection
200
C to 400
C
Forced Convection
100
C to 150
C
3.2.3.1. Heat Load
The heat load may consist of two types: active or passive, or a combination of the two.
An active load is the power which is dissipated by the device being cooled. It is generally
equal to the input power to the device. Passive heat loads are parasitic in nature and may
consist of radiation, convection or conduction.
3.2.3.1.1. Active Heat Load
Qactive = V2
/R = VI = I2
R
Qactive = active heat load (W)
V = voltage applied to the device being cooled (volts)
R = device resistance (ohms)
I = current through the device (amps)
3.2.3.1.2. Radiation
Q= F e s A (Tamb
4
–Tc
4
)
Qrad = radiation heat load (W)
F = shape factor (worst case value = 1)
e = emissivity (worst case value = 1)
s = Stefan-Boltzmann constant (5.667 X 10-8
W/m2
K4
)
A = area of cooled surface (m2
)
Tamb = Ambient temperature (0
K),
TC = TEC cold ceramic temperature (0
K),
3.2.3.1.3. Convection
Qconv = h A (Tair - Tc)

42
Qconv = convective heat load (W)
h = convective heat transfer coefficient (W/m2 0
C)
A = exposed surface area (m2
)
Tair = temperature of surrounding air (0
C)
TC = temperature of cold surface (0
C)
Table 3.3: Typical values of convection heat transfer coefficient
Process h (W/m2 .0C)
Free Convection – Air 2-25
Forced Convection – Air 25-250
3.2.3.1.4. Conduction
Qcond= (k A) (ΔT)/ (L)
Qcond = conductive heat load (W)
A = cross-sectional area of the material (m2
)
L = length of the heat path (m)
ΔT = temperature difference across the heat path (0
C)
3.2.3.1.4. Transient
Some designs require a set amount of time to reach the desired temperature. The
following equation may be used to estimate the time required:
T = [(Rho) (V) (Cp) (T1-T2)]/Q
Rho= Density (g/cm3
)
V = Volume (c m3
)
Cp = Specific heat (J/g 0
C)
T1-T2 = Temperature change (0
C)
Q = (Qto + Qtt) / 2 (W)

43
Qto is the initial heat pumping capacity when the temperature difference across the cooler
is zero. Qtt is the heat pumping capacity when the desired temperature difference is
reached and heat pumping capacity is decreased.
3.2.4. Entire Assembly of Peltier Module
TE module (Fig. 3.11) complete seize (40×40×4) mm, Flatness/parallelism is 0.05mm. In
this all TE elements are assembled in series by soldering (T100: BiSn (Melting
Point=138ºC)) from analysis known that each TE couple max. resistance is about 9.4489
milliohms (Total No. TE couples: 127), total TE module resistance (9.4489×127=12 Ω)
in same manner each couple takes optimum voltage of: 10mV, Total TE module
optimum voltage (10×127=12.7V).
Fig. 3.11: Bi2Te3 TE Module of 127 thermocouples.
Table 3.4: Bi2Te3 TEC module practical parameters observations at 210
C.
Observations
P Type material Seebeck coefficient (α1) 5×10-4
V/K
N Type material Seebeck coefficient (α2) -7.2 ×10-5
V/K
Thermal Conductivity (k) 1.5 W/ K
Effective Thermal Conductance (U) 0.06 W/ K
Resistivity ( ρ) 1×10-5
Ωm
Figure of merit (Z) 2.67×10-3

44
3.3. Preparation of Heat Sink CAD Model:
Fig. 3.13 shows the CAD model of the heat sink consists of equally spaced radial fins
attached to the central cylindrical core. In application, the heat sink under study is
mounted over the Peltier module for easy dissipation of the heat, and analyzed steady
state heat transfer in ANSYS 2019 R3.
3.3.1. Heat Material and Design
Material used for heat is Aluminum 6063 alloy. It is a medium strength alloy commonly
referred to as an architectural alloy. It is normally used in intricate extrusions. It has a
good surface finish; high corrosion resistance is readily suited to welding and can be
easily anodized. Provide good extrudability.
Table 3.5: Heat sink material properties.
S.No Properties Value
1 Density (ρ) 2719 kg/m3
2 Specific heat (Cp) 871 J/KgK
3 Thermal conductivity(k) 202.4 W/mK
3.3.1.1. Heat Sink Dimensions
Radius of heat sink cylindrical core r = 10mm
Radius of Thin fins from cylinder R1= 40mm
Radius of Thick fin from cylinder R2 = 42.5mm
Radius of Thick fin mounting C-clamp Cr = 2.5mm
Mounting C-clamp edges internal distance Ci = 1.5mm
Thickness of Thin fin tf1 = 0.80mm
Thickness of Thick fin tf2 = 1.80mm
Thickness of C-clamp Ct= 1.00mm
Height of Heat sink Hf = 28mm

45
Height of Heat sink Base Hb = 2.00mm
Angle between thin fins θ1 = 10 0
C
Angle between thick fins θ2 = 110
C
Heat sink base Bw= 41.5mm
No. of Thin fins = 44 No.
No. of Thick fins = 4mm
Fig. 3.12: Sectional and side view of heat sink.
Fig. 3.13: Heat sink 3D isometric view.
3.3.2. Heat Transfer Principle
Heat sink works on the principle of Fourier’s law of heat conduction, simplified to a one-
dimensional form in the x-direction, shows that when there is a temperature gradient in a
body, heat will be transferred from the higher temperature region to the lower
temperature region. The rate at which heat is transferred by conduction qk, is

46
proportional to the product of the temperature gradient and the cross-sectional area
through which heat is transferred
qk = - kA
dT
dx
------ (3.11)
Consider a heat sink in a duct, where air flows through the duct. It is assumed that the
heat sink base is higher in temperature than the air. Applying the conservation of energy,
for steady-state conditions, and Newton’s law of cooling to the temperature nodes shown
in the diagram gives the following set of equations:
Q = mcp.in (T air out -T air out) ------ (3.12)
Q =
T hs − Tair avg
Rhs
------ (3.13)
Where
Tair avg =
T air in + T air out
2
------ (3.14)
Fig. 3.14: Heat thermal resistance configuration.
The heat sink model consists of three resistances (Fig. 3.14), namely the resistance of the
thermal grease(0.197W/m 0
C) which connects source and sink R1, resistance of heat sink
R2 in this its base Rb, and the resistance of the fins is Rf. The heat sink thermal resistance
can be written as follows if the source is a uniformly applied to the heat sink base. If it is
not then the base resistance is primarily spreading resistance:

47
Rb =
t b
kAb
------ (3.15)
Where tb is the heat sink base thickness, k is the heat sink material thermal conductivity
and Ab is the area of the heat sink base. The thermal resistance from the base of the fins
to the air Rf, can be calculated by using the following formulas:
Rf =
1
nh f w f(t f + 2ƞ f If)
------ (3.16)
Once the heat sink and fin resistances are known, and then the heat sink thermal
resistance can be calculated as
R2 = Rb + Rf ------ (3.17)
Using the mean air temperature is an assumption that is valid for relatively short heat
sinks. When compact heat exchangers are calculated, the logarithmic mean air
temperature is used and m is the air mass flow rate in kg/s.
The above equations show that when the air flow through the heat sink decreases, this
results in an increase in the average air temperature. This in turn increases the heat sink
base temperature. And additionally, the thermal resistance of the heat sink will also
increase. The net result is a higher heat sink base temperature. The inlet air temperature
relates strongly with the heat sink base temperature. For example, if there is recirculation
of air in a product, the inlet air temperature is not the ambient air temperature. The inlet
air temperature of the heat sink is therefore higher, which also results in a higher heat
sink base temperature. If there is no air flow around the heat sink, energy cannot be
transferred. A heat sink is not a device with the “magical ability to absorb heat like a
sponge and send it off to a parallel universe”. Natural convection requires free flow of air
over the heat sink. If fins are not aligned horizontally, or if fins are too close together to
allow sufficient air flow between them, the efficiency of the heat sink will decline. The

48
Sketch of a heat sink in a duct used to calculate the governing equations from
conservation of energy and Newton’s law of cooling is as shown in Fig. 3.15.
Fig. 3.15: Sketch of a heat sink in a duct used to calculate the governing equations from
conservation of energy and Newton’s law of cooling.
3.3.3. Assumptions for Thermal Analysis of Heat Sink
The performance of the heat sink is determined by the various parameters like the heat
transfer coefficient, Fin efficiency, etc.
3.3.3.1. Heat Transfer Coefficient (h)
To define the heat transfer coefficient consider the Newton’s law of convection given by
the equation
Q = hAS (TS - TA)
=>h =
Q
As (Ts −TA)
------ (3.18)
Ƞ =
tanh mL
mL
------ (3.19)
Where m = √
hP
kf A

49
h = heat transfer coefficient of fin, P = Perimeter of fin = 2(W+ t), L = Length of fin. Kf
= thermal conductivity of Aluminum fin = 202.4 W/mK, A= Area of fin = W x t
Computational system gives a subjective or even quantitative forecast of fluid streams.
Re-enactment can give forecast of stream wonders utilizing the ANSYS 19.0 workbench
software for every single sought quantity, with high determination in space and time and
basically any issue and practical working conditions. On the other hand, if
discriminating, the outcomes should be worked.
The modeling of cylindrical cored radial fin heat sink is made by ANSYS workbench
software. This analysis is based on the following assumptions:
1) The fins are with adiabatic tip.
2) The fluid, air is assumed to be incompressible throughout the process. The airflow is
normal to the fins.
3) Air properties are taken at film temperature.
4) There are no heat sources within the fin itself.
5) The radiation heat transfer is negligible.
6) The temperature at the base of the fin is uniform.
3.3.4. FEM of Heat Sink:
In the present work, the software ANSYS 19.0 has been used to model and simulate Heat
transfer and CFD analysis of heat sink with radial fins attached to the central cylindrical
core.
3.3.4.1. Preparation of the Design Model
The design of heat Sink with radial rectangular fins are extruded from center cylindrical
core as shown in Fig. 3.13 is done in ANSYS Workbench 19.0 R3. Heat sink consist of
215-faces, 635-edges, 418-vertices, base face surface area is 1098.2 mm2
, radial fin

50
surface area is 14.007 mm2
, clamp pin surface area is 65.372mm2
, Fin height for all
models is 30 mm. There are total 48 numbers of fin in circular array with 11 rectangle
fins in each pattern and 1 clamp fin in each sectional column with fin spacing of 10
degrees between them. Total volume of heat sink is 32946 mm³.
3.3.4.2. Geometry of Heat Sink
The top view and front views of the 2D geometry and 3D model in enclosure are shown
in figures 3.12, 3.13 and, 3.15 respectively. The detailed material properties of the heat
sink are shown in the table 3.5 and for Peltier module base plate (40×40×3.9) mm (Table
3.6); properties of air are tabulated in Table 3.7.
Table 3.6: Properties of AL2O3 (TE Ceramic base plate).
1 Density (ρ) 3.7e-06 kg/mm3
2 Specific heat constant pressure 8.8e+05 mJ/kg.0
C
3 Isontropic Thermal conductivity (k) 0.024 W/mm0
C
Table 3.7: Properties of air.
1 Density (ρ) 1.225e-09 kg/mm3
2 Specific heat constant pressure 10064e+06 mJ/Kg.0
C
3 Viscosity ( Kg/m-s) 1.7894e-05
4 Isontropic Thermal conductivity (k) 2.42e-05W/mm.0
C
3.3.4.3. Mesh Generation & Simulation
The heat sink model is imported in to the work bench design modeler and meshed with a
four node three dimensional square element of 1mm the meshed model of the heat sink is
as shown in the below Fig. 3.16(a). The mechanical APDL (ANSYS Parametric Design
Language) solver is used to mesh the heat sink. No. of Nodes: 1477060, elements:

51
229830, bounding box diagonal: 131.89mm, average surface area: 461.32mm2, min edge
length; 6.2613e-002mm. Fig. 3.16(b) shows quality of mesh.
Fig. 3.16: Meshing and element quality of the heat sink model (1mm).
3.3.4.4. Loading Boundary Conditions
Fig. 3.17: Loading and boundary conditions and convection.
For steady state thermal analysis 1100
C heat is given as input to the ceramic base plate.
A convection coefficient of 5e-06W/mm2
.0
C has been applied to the remaining surfaces
of heat sink body.
3.3.4.5. Solution
Using Mechanical APDL solver, the maximum and minimum temperatures, heat fluxes
of the heat sink have been estimated. Then the result pertaining to steady state thermal
analysis involves temperature and heat flux its directions contours are explained are
explained below:

52
3.3.4.5.1. Temperature Distribution
The temperature is distribution obtained with 110. 0
C of maximum temperature at the
centre of the base plate and minimum temperature of 101.1.0
C is obtained at the fin
bottom end tips, at fin surface area 104.74.0
C temperature observed also at top of heat
sink around base plate surrounding observed 107.66.0
C temperature. The simulated result
is as shown in Fig. 3.18 & 3.19. a) Shows temperature distribution bottom ceramic plate
b) Bottom view of heat sink c) Bottom view of ceramic plate.
Fig. 3.18: Temperature distribution over heat sink (isometric view).
Fig. 3.19: Temperature distribution simulation in different views.

53
3.3.4.5.2. Heat Flux Distribution& Direction
The total heat flux distribution orientation to Y-axis obtained with maximum of 0.15953
W/mm2
.0
C and minimum of 0.0003633 W/mm2
.0
C from the simulated result as shown in
Fig 3.20, Maximum direction of heat flux in X-axis is 0.11847 W/mm², minimum is
0.12943 W/mm² and average is 1.2256e-004 W/mm².
Fig. 3.20: Heat flux and Directional heat flux (x-axis) distribution simulation.
3.4. Axially Curved Cooling Fan Design:
The axial flow fan is extensively used in many engineering applications. This type of
fan is used in a wide variety of applications, ranging from small cooling fans for
electronics to the giant fans used in wind tunnels. The extended use of axial flow fans for
fluid movement and heat transfer has resulted in detailed research into the performance
attributes of many designs. Numerical investigations have been performed to quantify
the performance of axial fans and their flow characteristics. Axial fans blow air along

54
the axis of the fan, linearly, hence their name. The axial-flow fans have blades that force
air to move parallel to the shaft about which the blades rotate (Fig. 3.21).
Fig. 3.21: Airflow mechanism in an axial fan.
Modeling and analysis are done using CFD software. The design of the axial fan blades
and hub, casing was done in ANSYS workbench. The present work is carried out to find
the various contours (such as pressure contour and velocity contour, eddy viscosity and
turbulence kinetic energy) streamlines under steady conditions for nine bladed axial fan.
The key and important outcomes of this study are as follows:
1. CFD results were presented in the form of velocity vectors and path lines, which
provided actual flow characteristics of air around the fan for different blade
orientations. Detection of high and low air flow regions with recirculation and
vortices immensely improved understanding of flow in the complex system studied,
which helped to understand the complications involved in air recirculation.
2. This study showed how the flow of air was interrupted by the hub obstruction,
thereby resulting in unwanted reverse flow regions.
3. The CFD results were in agreement with the experimental data measured during
physical testing. Any error was probably a result of the experimental conditions,
fluctuations of fan rev/min, or the considered ideal condition while simulating the

AN EXPERIMENTAL DESIGN & ANALYSIS OF PORTABLE USB POWERED THERMO ELECTRIC COOLER

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