Faculty of Electrical Engineering - Universiti Teknologi Malaysia
UNIVERSITI TEKNOLOGI MALAYSIA
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name :
NUR AYUZIE AKMAL BINTI MUHAMMAD
Date of birth
:
6 JULY 1987
Title
:
MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC
Academic Session:
2009/2010
I declare that this thesis is classified as:
√
CONFIDENTIAL
(Contains confidential information under the Official Secret Act 1972)*
RESTRICTED
(Contains restricted information as specified by the organisation where research was done)*
OPEN ACCESS
I agree that my thesis to be published as online open access (full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows: 1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only. 3. The Library has the right to make copies of the thesis for academic exchange. Certified by:
SIGNATURE
870706-06-5818
PM.DR AZHAR KHAIRUDDIN
(NEW IC NO. /PASSPORT NO.)
NAME OF SUPERVISOR
Date: 29.APRIL.2010
NOTES :
SIGNATURE OF SUPERVISOR
*
Date: APRIL 2010
If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the organisation with period and reasons for confidentiality or restriction.
ii
“ I hereby declare that I have read this report and in my opinion this report has fulfil the scope and quality for the awarded of the degree of the Bachelor of Engineering (Electrical)”
Signature
:
Name of Supervisor : ASSOC. PROF. DR AZHAR KHAIRUDDIN Date
: APRIL 2010
iii
MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC.
NUR AYUZIE AKMAL BINTI MUHAMMAD.
A thesis submitted in partial fulfilment of the requirement for the award of the degree of Bachelor of Engineering ( Electrical ).
Faculty of Electrical Engineering Universiti Teknologi Malaysia.
APRIL 2010
iv
DECLARATION
I declare that this thesis entitled “MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC’ is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.
Signature
:
Name
: NUR AYUZIE AKMAL BINTI MUHAMMAD.
Date
: APRIL 2010
v
Dedicated to my beloved mother, my reason of living and the whole family for their understanding and all my lecturers at UTM. Thanks for everything.
vi
ACKNOWLEDGEMENT
First and foremost, I would like to express my heartily gratitude to my supervisor, PM.Dr. Azhar B Khairuddin for the guidance and enthusiasm given throughout the progress of this project.
My appreciation also goes to my family who has been so tolerant and supports me all these years. Thanks for their encouragement, love and emotional supports that they had given to me.
I would also like to thank Dr Wan Azli, lecturer of Falculty of Science and Faculty of Mechanical (FKM) Lab Technician, Mr.Zamri Mat Saman for his cooperation, guidance and helps in the project.
Nevertheless, my great appreciation goes to all my friends and those who involve directly or indirectly with this project. There is no such meaningful word than.
Thank You So Much.
vii
ABSTRACT
As known widely, compressor refrigerator is commonly use in large refrigerator and well known efficient than absorption refrigerator. One of the absorption refrigerators is thermoelectric refrigerator, which use in small size refrigerator is quiet running and very environmental friendly. However, it uses more electricity, poor coefficient performance and small cooling capacity. So in order to improve it, an investigation have been run in this project by considering the common semiconductor material in market, then investigate it parameter and may as one way to improve its effectiveness. Therefore, in this project focused on the configuration of two stage semiconductor thermoelectric cooler, especially investigating the effect of some parameters, such current in second stage I2, the area of every thermocouple A, and the number of thermocouple in second stage N, on the cooling performance of thermoelectric module. The theoretical analysis and simulating calculation were conducted for basic two stage of thermoelectric module using DEV-cpp software. The obtained result of analysis indicate that changing current in second stage I2, the area of every thermocouple A, and number of thermocouple in second stage N, can improve cooling performance of the module. These results can be used to optimize the configuration of two stage thermoelectric module and provide guides for designing and application of thermoelectric cooler.
viii
ABSTRAK
Di ketahui sedia maklumnya, penyejuk jenis pemampatan selalu digunakan di dalam penyejuk bersaiz besar serta lebih cekap dari penyejuk jenis penyerapan. Salah satu dari pada penyejuk jenis penyerapan ialah penyejuk termoelektrik yang digunakan di dalam penyejuk bersaiz lebih kecil, berfungsi dengan senyap dan mesra persekitaran. Walaubagaimanapun, ia memerlukan lebih tenaga elektrik, rendah pekali perlaksanaan dan kapasiti penyejukkan. Oleh yang demikian, untuk memperbaiki kekurangan itu penyelidikan dijalankan dalam projek ini dengan mempertimbangkan bahan separuh konduktor yang selalu digunakan di pasaran, kemudian mengkaji parameter berkaitan dan sebagai salah satu cara untuk memperbaiki keberkesanannya. Oleh itu, dalam projek ini tertumpu kepada konfigurasi modul termoelektrik dusa aras, terutamanya mengkaji kesan beberapa parameter seperti arus di aras dua I2, luas setiap pasang bahan termo A, dan bilangan pasangan bahan termo di aras dua N, terhadap tahap penyejukkan modul termoelektik. Analisis secara teori dan pengiraan simulasi di jalankan terhadap modul asas dua aras termoelektrik menggunakan program komputer DEV-cpp. Hasil keputusan yang didapati menunjukkan perubahan arus elektrik di aras dua, luas setiap pasang bahan termo dan bilangan pasangan bahan termo di aras dua dapat memperbaiki tahap penyejukan modul ini. Hasil analisis ini juga digunakan untuk memperoleh konfigurasi optimum untuk termoelektrik dua aras modul dan dapat memberikan panduan untuk rekaan atau aplikasi yang melibatkan penyejuk termoelektrik.
ix
TABLE OF CONTENTS.
CHAPTER
1.0
2.0
TITLE
PAGE
DECLARATION OF THESIS
Iv
DEDICATION
v
AKNOWLEDGEMENT
vi
ABSTRACT
vii
ABSTRAK
viii
TABLE OF CONTENTS
ix
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF SYMBOLS AND ABBREVIATIONS
xiv
LIST OF APPENDICES
xv
INTRODUCTION 1.1 Background
1
1.2 Problem Statement
5
1.3 Objectives
5
1.4 Scope of Project
6
1.5 Outline of the thesis
6
LITERATURE REVIEW 2.1 Chapter Overview
8
2.2 Thermoelectric
8
2.2.1 Parameters
10
2.2.2 Mathematical Equations
11
2.3 Performance of Thermoelectric
13
2.4 Summary
14
x
3.0
METHODOLOGY 3.1 Chapter Overview
15
3.2 Project Process
16
3.2.1 Mathematical Development
17
3.2.2 Software Implementation.
19
3.2.3 Analysis
23
3.3 Summary
4.0
24
RESULTS AND DISCUSSIONS 4.1 Chapter Overview
25
4.2 Result Analysis
25
4.2.1 Set 1: The Efficient Size
26
4.2.2 Set 2: Effect of the current of second
27
stage. 4.2.3 Set 3: Effect of the area of every
30
Thermocouple 4.2.4 the optimum configuration of
33
Thermoelectric module. 4.3 Summary
5.0
35
CONCLUSIONS AND RECOMMENDATIONS. 5.1 Conclusions
37
5.2 Recommendations.
38
REFERENCES
39
APPENDICES
40
xi
LIST OF TABLES
TABLE NO
TITLE
PAGE
4.1
Selected data from the coding output
26
4.2
Data of SET 2 from coding output-for current of 28 second stage.
4.3
Data of SET 2 from coding output-for area of 31 every of thermocouple effect.
xii
LIST OF FIGURES
FIGURES NO. 1.1
TITLE Conventional
arrangement
PAGES for
thermoelectric
2
Schematic of thermoelectric module operation (a)
4
cooler. 1.2
cooling mode; (b) heating mode. 2.1
A real thermoelectric refrigerator cooler.
9
2.2
Simple thermoelectric refrigerator.
13
3.1
Planning
16
3.2
Schematic diagrams of multicouple thermoelectric
17
3.3
Flow chart of coding simulation
20
3.4
The coding display
21
3.5
Show the compile the coding step, if there no error,
21
data can be displayed later. 3.6
Data output for SET 1.
22
3.7
Data output for SET 2-will use also for SET 3
23
4.1
Graph type of size versus current, I
27
4.2
The coefficient of performance versus the current
29
and number of couple in the second stage 4.3
The rate versus the current and the number of thermocouple in second stage
30
xiii
4.4
The coefficient of performance versus the area of
32
every thermocouple and number of couple in the second stage. 4.5
The cooling rate versus the area and the number of
33
thermocouple in the second stage. 4.6
The coefficient of performance versus the current in second stage, with several of area of every thermocouple and number of couple in the second stage
34
xiv
LIST OF SYMBOLS AND ABBREVIATIONS
I
Electrical current (A)
K
Thermal conductance of thermocouple (W/K)
A
Cross-sectional area of every thermocouple (cm2)
L
The length of thermocouple (cm2)
R
Electrical resistance of a thermocouple (Ω)
N
The number of thermocouple in second stage
qc
Heat flow rate of a thermocouples at the cold junction (W)
qh
Heat flow rate of a thermocouples at the hot junction (W)
QC
Cooling capacity of semiconductor thermoelectric module (W)
QH
Rejected heat flow of the thermoelectric module (W)
Α
Seeback coefficient (V/K)
α
Electrical resistivity (Ωcm)
k
Thermal conductivity (W/Kcm)
ε
Coefficient of performance
P
p-type semiconductor
n
n-type semiconductor
xv
LIST OF APPENDICES.
Title
Pages
APPENDIX A
39
APPENDIX B
43
1
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
A refrigerator is cooling appliance comprising of a thermally insulated compartment and a heat pump. These configurations allows respectively chemical and mechanical means of heat transfer from it to the external environment in order to cool the contents to that below ambient temperature. With the current technology development, there are many types of cooler used in refrigerator. Basically, refrigeration system can be divided into two types; compression
refrigerator
system
and
absorption
refrigerator
system.
Compression refrigerator, which is commonly used, normally make noticeable noise. The absorption refrigerator is different from compressor refrigerator. It operates based on the combustion of liquefied petroleum gas, solar thermal energy or an electric heating element. It is quieter than compressor motor in a typical refrigerator because it has no moving part.
Absorption refrigerator is also known as thermo-electric Peltier units which used quiet running is required; Peltier cooler are used in the smallest refrigerators as they have bulky mechanism. The thermoelectric coolers have been used widely in space, military, telecommunication and other applications
2 for cooling and stabilizing the devices temperature. Thermoelectric domestic heat pumps and air conditioners will become competitive in the world market. This is because energy costs and demands can only increase and environmental concerns can only increase. Also the environmental treaties have banned chlorofluorocarbons. Reduced manufacturing costs of thermoelectric devices have been opening up new markets.
Commercially available thermoelectric devices are very reliable when used as coolers and operated at temperatures below room temperature. Usually, thermoelectric coolers are used in cases where the cooling system design criteria includes such factors as high reliability, small size, low weight, intrinsic safety for hazardous electrical environments, and precise temperature control. A thermoelectric cooling system has an electric circuit including a direct current power source providing direct current through the electric circuit, a thermoelectric device has at least one heat sink and at least one heat source capable of being cooled to a predetermined temperature range, and a control assembly. The use of a thermoelectric device in a cooling system has conventionally followed the basic arrangement shown in Figure 1.1.
Figure 1.1. Conventional arrangement for thermoelectric cooler. Q1 is the heat to be pumped, P is the electrical power supplied. Q2 is the heat dissipated to the ambient.
3 Thermoelectric cooling systems are analogous to conventional refrigeration
systems.
A
thermoelectric
cooling
system
has
similar
subassemblies. However, thermoelectric cooling is specifically the abstraction of heat from electronic components by the Peltier effect. Potential uses range from the cooling of electronic components to domestic refrigerators and air conditioner for cooling/heating a room space as mention before.
Thermoelectric refrigeration is achieved when a direct current is passed through one or more pairs of n- and p-type semiconductor materials. Fig. 1.2 is a diagram of a single pair consisting of n- and p-type semiconductor materials. In the cooling mode, direct current passes from the n- to p-type semiconductor material. The temperature TC of the interconnecting conductor decreases and heat is absorbed from the environment. This heat absorption from the environment (cooling) occurs when electrons pass from a low energy level in the p-type material through the interconnecting conductor to a higher energy level in the n-type material. The absorbed heat is transferred through the semiconductor materials by electron transport to the other end of the junction TH and liberated as the electrons return to a lower energy level in the p-type material. This phenomenon is called the Peltier effect.
A second phenomenon is also important in thermoelectric refrigeration. When a temperature differential is established between the hot and cold ends of the semiconductor material, a voltage is generated. This voltage is called the Seebeck voltage, and it is directly proportional to the temperature differential. The constant of proportionality is referred to as the Seebeck coefficient.
4
Figure 1.2; Schematic of thermoelectric module operation (a) cooling mode; (b) heating mode.
5 1.2
PROBLEM STATEMENT
As known widely, compressor refrigerator is commonly use in large refrigerator and well known efficient than absorption refrigerator. Specify to thermoelectric refrigerator, it use in small size refrigerator, quiet running and very environmental friendly. However, it uses more electricity, poor coefficient performance and small cooling capacity. So in order to improve it, an investigation have been run in this project by considering the common semiconductor material in market, then investigate it parameter and may as one way to improve its effectiveness. In this project developed an analysis base on condition of the material such as it cross sectional area and number of thermocouple.
1.3
OBJECTIVES.
The objectives of the project are: i.
To model the thermoelectric cooler module to analysis it performance.
ii.
To analyze the cooling performance of thermoelectric cooler by changing the second stage current, area of thermocouple and number of thermocouple on second stage.
iii.
To know the optimize configuration of the 2 stage thermoelectric cooler based on parameter that investigated.
6 1.4
SCOPE OF PROJECT.
The scopes of the project are: i.
The performance of the thermoelectric will measure base on the value of coefficient of performance (COP) and the cooling capacity.
ii.
Then in order to determine all the performance, there are few parameter that will be measured during testing such as; cross sectional area (A), current varying in second stage (I), number of thermocouples (N) and other basic parameter such voltage.
iii.
Selecting the best semiconductor material that commonly use in market.
1.5 OUTLINE OF THE THESIS.
The thesis is divided into five chapters mainly. The first chapter discussed on the significant of the project. This includes the problem statement, objectives and the scope of the project. In Chapter 2, the literature review of the project stated. This chapter discussed the theory about thermoelectric module in detailed that support the introduction of this project from various sources. This is important to support why project should be done. Furthermore, there are some relevant fact and equation for this module stated.
In Chapter 3, methodology discuss on the project process which generally
divided
into
three,
mathematical
development,
software
implementation and analysis of data. In this chapter also shows step by step of each process were developing. The next Chapter 4, results and discussion were stated. Each of the data analysis discussed by separate it into 4 parts. There are discussion on the efficient size, effect of the current on second stage, effect of
7 the area of every thermocouple and the optimum configuration of thermoelectric module.
Lastly, Chapter 5 on conclusion and recommendations. In this chapter will conclude all the analysis with relevant fact and also recommendations stated for next studies.
8
CHAPTER 2
LITERATURE REVIEW
2.1 CHAPTER OVERVIEW.
As mention in previous chapter the introduction of absorption refrigerator- thermoelectric cooler general information, application and advantages. Then as state in problem statement section 1.2, the thermoelectric coolers need to improve it poor coefficient of performance and small cooling capacity. As one of the alternatives in solving this problem, in this project will develop some parameter such as cross sectional area and number of thermocouple. Generally the connection of thermoelectric cooler model as shown in figure 2.1.
9
DC source
semiconducto r material, n-type p-type
Conductor material
Figure 2.1 ; A real thermoelectric refrigerator cooler.
This chapter explains in detail about parameter that will consider in this project analysis that will affect the performance of thermoelectric based on several of source.
2.2 THERMOELECTRIC.
Currently, the one-stage semiconductor thermo-electric module is composed of a large number of thermocouples connected electrically in series and thermally in parallel. A thermocouple is made of a p-and a n-type semiconductor. A two-stage semiconductor thermoelectric module is stacked by one group of thermocouples on the top of the other, which is connected
10 thermally in series. In an actual operation, the working electric currents for them are in series or in parallel. Two types of two-stage thermoelectric coolers are both used in semiconductor thermoelectric refrigeration, and the types with separate electrical currents may have the best performance [1]. Therefore, the type of two-stage thermoelectric cooler with separate working electrical currents was selected as the model in this study. For simplicity, there is only one thermocouple in the second stage, but several thermocouples in the first stage for this module, as shown in Fig.1.1. In addition, a piece of thermally conductive but electrically insulating ceramic plate is placed between the first stage and the second stage.
2.2.1
PARAMETERS
As mention in objectives, by changing the current in second stage, area of thermocouple and number of thermocouple on second stage will affect the cooler performance, also mention by other researcher; that improvement of thermoelectric parameter that relate to thermocouple element and module are equally important in designing a high performance of thermoelectric cooler[1].
In semiconductor thermoelectric refrigeration, there are many factors influencing the performance of refrigeration such as thermoelectric materials, size of thermocouple and electrical current that supply to the circuit[2]. Before this an presented a method to improve the cooling capacity and coefficient of performance for two stage thermoelectric cooler based on the influences of the allocation of the junction temperature difference in the module and the length of thermocouple[2].
In this project also more emphasized on using of two-stage of thermoelectric modules because, it well known that two-stage semiconductor thermoelectric modules are often used for extending operation testing[3].In
11 addition, the performance of the coolers are not only depends on physical properties of the thermocouples, but also on the configuration of two-stage thermoelectric[4].Therefore, in this project will consider the area of thermocouple, current in second stage and number of thermocouples. Furthermore, in previous work, emphasized more on the effect of the length of the thermocouples but the effect of the area of thermocouple was not considered deeply.
In order to use material that will use in the project, it needs to identify its properties and capability. Most cooling unit are required to function in the region of room temperature [4] therefore, in this project use Bi2Te2-Bistmuth telluride which known as best material function in room temperature [5]. This general properties of material need to be consider as one of it specification that will be use later during analysis and as precaution. The general properties of material that will consider; specific heat of material- it high temperature and lowest temperature, it melting point, thermal expansion coefficient and others[5].The other material capability needs to consider are Seeback coefficient, electrical resistivity and thermal conductivity because refrigeration capability of semiconductor material is dependent of combined effect all above properties[6]. Since the scope of this project are not cover those parameter, so all of it will directly taking from manufacturer. Some of the information will use in calculation of performance by using c-programming later and the rest is for addition information.
Therefore, in this project the optimum configuration of a basic twostage semiconductor thermoelectric module was studied by investigating the current of the second stage, the area of thermocouple and the number of thermocouples. The analysing the effect of those parameters on cooling performance, the optimum performance relation obtained.
12 2.2.2
MATHEMATICAL EQUATIONS.
In order to figure out the performance of the thermoelectric cooler in this project need to carry out some equation that will involving during analysis. The cooling capacity of thermoelectric module is thus defined as 2 𝑞𝑐 = 𝛼2 − 𝛼1 𝐼𝑇𝑐 − 𝐼 𝑅 2 − 𝐾(𝑇𝐻 − 𝑇𝐶 )
(2.0)
Where the total electrical resistance of the branches in series is;
𝑅 =
𝑙1 𝐴 1 𝜎1
+
𝑙2 𝐴 2 𝜎2
(2.1)
And the total thermal conductance of the branches in parallel;
𝐾 =
𝐴1 𝑘 1 𝑙1
+
𝐴2 𝑘 2 𝑙2
(2.2)
The input power equation; 𝑤 = 𝛼2 − 𝛼1 𝐼 𝑇𝐻 − 𝑇𝐶 + 𝐼 2 𝑅
(2.3)
The total heat rejection equation; 𝑞ℎ = 𝑤 + 𝑞𝑐
(2.4)
And then coefficient of performance (COP);
∅=
𝑞𝑐 𝑤
(2.5)
Where,
qc= cooling capacity of semiconductor thermoelectric module (W) qh= rejected heat flow of the thermoelectric module (W). 𝛼 = seeback coefficient.
13 A = cross sectional area T = temperature of source and sink ( H and C) 𝑙 = length 𝜎 = electrical conductivity 𝑘 = thermal conductivity 𝐼 = current through the thermoelectric module (amp) [5],[1].
Figure 2.2 shows a simple model of thermoelectric structure where heat source side labelled as TC and heat sink side labelled as TH.
14
HEAT SOURCE Tc
I 2 1 + _ HEAT SINK TH Figure 2.2; Simple thermoelectric refrigerator.
From all the parameters of this project has been get from industry that produce the material. The electrical and thermal conductivity of material can be known by manufacturer that have running an experiment to test their product. As mention by K.H.Lee; the parameters such as temperature different, current, thickness of thermoelectric element, and the number of thermoelectric pairs will affect the performance [7].The thick element with larger number of thermoelectric pairs or the cross sectional areas of every element also improve the cooling performance [2],[4].
2.3 PERFORMANCE OF THERMOELECTRIC.
In this project the performance of thermoelectric cooler will measure by using analysis of coefficient of performance (COP) and its cooling capacity. As mention in previous 2.2.2 section, selection of material by considering their parameter, where parameters such as temperature different, current, thickness of thermoelectric element, and the number of thermoelectric pairs will affect the performance[7]. Known in equation COP and cooling capacity relate with all those parameter.
15 Normally, the coefficient of performance (COP) is the primary factor to evaluate the performance of the cooler [7] and it used to define the cooling “efficiency” where, the net heat absorbed at the cold end divided by applied electric power [6]. The analysis can be done by the COP varies with the parameters [1].
2.4
SUMMARY
The chapter has presented the parameter that considered in analysis performance of thermoelectric cooler and relevant equations that related to parameter which leading to measuring the performance of thermoelectric cooler. This is to be followed by discussion on methodology that had been used in this project in the next chapter
16
CHAPTER 3
METHODOLOGY.
3.1 CHAPTER OVERVIEW
This chapter will discuss about methodology that have been used to achieve the objective of the project. Overall, the project is divided into three parts, finding material data and properties, coding simulation and analysis.
17 Figure 3.1 show the flow chart of the project planning that has been developed in this project. Investigate equation
Investigate the relevant mathematical equation
Get the data and specification from industry
software
Running coding simulation-transform output into graph using M.O.Excel
analysis
Analysis all the output in term of performance
Figure 3.1; Planning
3.2 PROJECT PROCESS
Figure 3.1 shows the process of this project that separately into three parts, selecting mathematical equation, software and analysis.
18
3.2.1
MATHEMATICAL DEVELOPMENT.
In this project there are several equations that relate will be use which leading in gaining the coefficient of performance and cooling capacity. All the equation has been state in previous chapter. (2.2.2-mathematical equation)
The thermoelectric cooler for this project will design based on the real thermoelectric refrigerator cooler in Figure 3.2 The different on number of thermocouple/thermoelements in second stage while number of thermocouple in first stage will remain one pair only.
Figure 3.2; Schematic diagrams of multicouple thermoelectric modules. In this project also based on the concept where, for the first stage of thermocouple, the pumped heat rates at the cold side and rejected heat rates at the hot side can be express; 𝑞𝑐 and 𝑞ℎ similarly to the second stage. Then, in this project will used conventional analysis method for this thermoelectric module which not takes the effect of the thermal and contact resistance of both ceramic plates into consideration. By considering that a better thermal insulation is taken for the whole module, therefore the thermal resistances between two-stage and heat loss for the whole two-stage
19 thermoelectric module is neglected. Then following heat balance can be assumed;
Th2 = Tc1
(3.1)
qh2 = nqc1
(3.2)
Based on the equation, we can derive that cooling capacity at the cold side and the hot side of the whole two stage thermoelectric cooler are respectively as;
(3.3) (3.4)
Then coefficient of performance of two stage thermoelectric module is thus defined as; (3.5)
and current for second stage can be derived from equation which is written as; (3.6)
Using this set of equation, the module of thermoelectric the parameter will be test based on several of cross sectional area of the thermocouple element, number of thermocouple n and current I that varying.
The data and specification that obtained from manufacturer. MELCOR, USA state in appendix (B).There is 33 type of size and specification of material that use later.
20 3.2.2
SOFTWARE IMPLEMENTATION;
DESIGN OF CODING SIMULATION. All the data that get from manufacturer will be test using coding of mathematical equation that investigated. Generally, the coding is made in two sections. The first section in to determine the best size and the second section are to test all the parameter that consider as told before. Figure 3.3 show flow chart that represents the code.
Start.
Initialize data N=2 , I2=5.0A, α, λ, ρ ,TH, and TC
Calculate value K, R, I, Qc, Qh, and COP. no No operation
N
int main() { int n=0; double SUM, abselon, N=2.0, I2=5.0; double alfa=1.93e-4, lamda=1.9, ro=8.52e-6, Th=300, Tc=200; double K, R, I, Qc, Qh; double set[33][2]={ {.4,.5}, {.4,.8}, {.45,1.27}, {.5,.7}, {.5,1.0}, {.5,1.5}, {.52,1.6}, {.54,.76}, {.61,1.27}, {.61,1.52}, {.635,1.02}, {.65,1.0}, {.65,1.27}, {.81,1.27}, {.81,1.57}, {.85,.46}, {.85,1.27}, {.85,1.57}, {1.0,.46},
//[A][L]
41 {1.0,.64}, {1.0,1.27}, {1.0,1.3}, {1.0,1.57}, {1.0,1.65}, {1.0,2.03}, {1.2,1.4}, {1.2,1.91}, {1.36,.64}, {1.36,1.52}, {1.36,1.57}, {1.36,2.41}, {1.4,.4}, {1.4,.8}}; printf("SET 1\n\n");
printf("==A==============L========Abselon==========I=====\n");
do{ K=(2.0*lamda*pow(set[n][0]/1000.0,2))/set[n][1]; R=(2*ro*set[n][1])/pow(set[n][0]/1000.0,2); I=(alfa*Tc)/R; SUM = alfa*I*Tc - K*(Th-Tc); Qc = SUM - 0.5*I*I*R; Qh = SUM + 0.5*I*I*R; abselon = Qc/(Qh-Qc);
printf("%6.4e
%5.2lf
\n",pow(set[n][0]/1000.0,2),set[n][1],abselon,I); n++;
}while(n
DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name :
NUR AYUZIE AKMAL BINTI MUHAMMAD
Date of birth
:
6 JULY 1987
Title
:
MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC
Academic Session:
2009/2010
I declare that this thesis is classified as:
√
CONFIDENTIAL
(Contains confidential information under the Official Secret Act 1972)*
RESTRICTED
(Contains restricted information as specified by the organisation where research was done)*
OPEN ACCESS
I agree that my thesis to be published as online open access (full text)
I acknowledged that Universiti Teknologi Malaysia reserves the right as follows: 1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only. 3. The Library has the right to make copies of the thesis for academic exchange. Certified by:
SIGNATURE
870706-06-5818
PM.DR AZHAR KHAIRUDDIN
(NEW IC NO. /PASSPORT NO.)
NAME OF SUPERVISOR
Date: 29.APRIL.2010
NOTES :
SIGNATURE OF SUPERVISOR
*
Date: APRIL 2010
If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the organisation with period and reasons for confidentiality or restriction.
ii
“ I hereby declare that I have read this report and in my opinion this report has fulfil the scope and quality for the awarded of the degree of the Bachelor of Engineering (Electrical)”
Signature
:
Name of Supervisor : ASSOC. PROF. DR AZHAR KHAIRUDDIN Date
: APRIL 2010
iii
MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC.
NUR AYUZIE AKMAL BINTI MUHAMMAD.
A thesis submitted in partial fulfilment of the requirement for the award of the degree of Bachelor of Engineering ( Electrical ).
Faculty of Electrical Engineering Universiti Teknologi Malaysia.
APRIL 2010
iv
DECLARATION
I declare that this thesis entitled “MATHEMATICAL ANALYSIS OF PERFORMANCE OF THERMOELECTRIC’ is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.
Signature
:
Name
: NUR AYUZIE AKMAL BINTI MUHAMMAD.
Date
: APRIL 2010
v
Dedicated to my beloved mother, my reason of living and the whole family for their understanding and all my lecturers at UTM. Thanks for everything.
vi
ACKNOWLEDGEMENT
First and foremost, I would like to express my heartily gratitude to my supervisor, PM.Dr. Azhar B Khairuddin for the guidance and enthusiasm given throughout the progress of this project.
My appreciation also goes to my family who has been so tolerant and supports me all these years. Thanks for their encouragement, love and emotional supports that they had given to me.
I would also like to thank Dr Wan Azli, lecturer of Falculty of Science and Faculty of Mechanical (FKM) Lab Technician, Mr.Zamri Mat Saman for his cooperation, guidance and helps in the project.
Nevertheless, my great appreciation goes to all my friends and those who involve directly or indirectly with this project. There is no such meaningful word than.
Thank You So Much.
vii
ABSTRACT
As known widely, compressor refrigerator is commonly use in large refrigerator and well known efficient than absorption refrigerator. One of the absorption refrigerators is thermoelectric refrigerator, which use in small size refrigerator is quiet running and very environmental friendly. However, it uses more electricity, poor coefficient performance and small cooling capacity. So in order to improve it, an investigation have been run in this project by considering the common semiconductor material in market, then investigate it parameter and may as one way to improve its effectiveness. Therefore, in this project focused on the configuration of two stage semiconductor thermoelectric cooler, especially investigating the effect of some parameters, such current in second stage I2, the area of every thermocouple A, and the number of thermocouple in second stage N, on the cooling performance of thermoelectric module. The theoretical analysis and simulating calculation were conducted for basic two stage of thermoelectric module using DEV-cpp software. The obtained result of analysis indicate that changing current in second stage I2, the area of every thermocouple A, and number of thermocouple in second stage N, can improve cooling performance of the module. These results can be used to optimize the configuration of two stage thermoelectric module and provide guides for designing and application of thermoelectric cooler.
viii
ABSTRAK
Di ketahui sedia maklumnya, penyejuk jenis pemampatan selalu digunakan di dalam penyejuk bersaiz besar serta lebih cekap dari penyejuk jenis penyerapan. Salah satu dari pada penyejuk jenis penyerapan ialah penyejuk termoelektrik yang digunakan di dalam penyejuk bersaiz lebih kecil, berfungsi dengan senyap dan mesra persekitaran. Walaubagaimanapun, ia memerlukan lebih tenaga elektrik, rendah pekali perlaksanaan dan kapasiti penyejukkan. Oleh yang demikian, untuk memperbaiki kekurangan itu penyelidikan dijalankan dalam projek ini dengan mempertimbangkan bahan separuh konduktor yang selalu digunakan di pasaran, kemudian mengkaji parameter berkaitan dan sebagai salah satu cara untuk memperbaiki keberkesanannya. Oleh itu, dalam projek ini tertumpu kepada konfigurasi modul termoelektrik dusa aras, terutamanya mengkaji kesan beberapa parameter seperti arus di aras dua I2, luas setiap pasang bahan termo A, dan bilangan pasangan bahan termo di aras dua N, terhadap tahap penyejukkan modul termoelektik. Analisis secara teori dan pengiraan simulasi di jalankan terhadap modul asas dua aras termoelektrik menggunakan program komputer DEV-cpp. Hasil keputusan yang didapati menunjukkan perubahan arus elektrik di aras dua, luas setiap pasang bahan termo dan bilangan pasangan bahan termo di aras dua dapat memperbaiki tahap penyejukan modul ini. Hasil analisis ini juga digunakan untuk memperoleh konfigurasi optimum untuk termoelektrik dua aras modul dan dapat memberikan panduan untuk rekaan atau aplikasi yang melibatkan penyejuk termoelektrik.
ix
TABLE OF CONTENTS.
CHAPTER
1.0
2.0
TITLE
PAGE
DECLARATION OF THESIS
Iv
DEDICATION
v
AKNOWLEDGEMENT
vi
ABSTRACT
vii
ABSTRAK
viii
TABLE OF CONTENTS
ix
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF SYMBOLS AND ABBREVIATIONS
xiv
LIST OF APPENDICES
xv
INTRODUCTION 1.1 Background
1
1.2 Problem Statement
5
1.3 Objectives
5
1.4 Scope of Project
6
1.5 Outline of the thesis
6
LITERATURE REVIEW 2.1 Chapter Overview
8
2.2 Thermoelectric
8
2.2.1 Parameters
10
2.2.2 Mathematical Equations
11
2.3 Performance of Thermoelectric
13
2.4 Summary
14
x
3.0
METHODOLOGY 3.1 Chapter Overview
15
3.2 Project Process
16
3.2.1 Mathematical Development
17
3.2.2 Software Implementation.
19
3.2.3 Analysis
23
3.3 Summary
4.0
24
RESULTS AND DISCUSSIONS 4.1 Chapter Overview
25
4.2 Result Analysis
25
4.2.1 Set 1: The Efficient Size
26
4.2.2 Set 2: Effect of the current of second
27
stage. 4.2.3 Set 3: Effect of the area of every
30
Thermocouple 4.2.4 the optimum configuration of
33
Thermoelectric module. 4.3 Summary
5.0
35
CONCLUSIONS AND RECOMMENDATIONS. 5.1 Conclusions
37
5.2 Recommendations.
38
REFERENCES
39
APPENDICES
40
xi
LIST OF TABLES
TABLE NO
TITLE
PAGE
4.1
Selected data from the coding output
26
4.2
Data of SET 2 from coding output-for current of 28 second stage.
4.3
Data of SET 2 from coding output-for area of 31 every of thermocouple effect.
xii
LIST OF FIGURES
FIGURES NO. 1.1
TITLE Conventional
arrangement
PAGES for
thermoelectric
2
Schematic of thermoelectric module operation (a)
4
cooler. 1.2
cooling mode; (b) heating mode. 2.1
A real thermoelectric refrigerator cooler.
9
2.2
Simple thermoelectric refrigerator.
13
3.1
Planning
16
3.2
Schematic diagrams of multicouple thermoelectric
17
3.3
Flow chart of coding simulation
20
3.4
The coding display
21
3.5
Show the compile the coding step, if there no error,
21
data can be displayed later. 3.6
Data output for SET 1.
22
3.7
Data output for SET 2-will use also for SET 3
23
4.1
Graph type of size versus current, I
27
4.2
The coefficient of performance versus the current
29
and number of couple in the second stage 4.3
The rate versus the current and the number of thermocouple in second stage
30
xiii
4.4
The coefficient of performance versus the area of
32
every thermocouple and number of couple in the second stage. 4.5
The cooling rate versus the area and the number of
33
thermocouple in the second stage. 4.6
The coefficient of performance versus the current in second stage, with several of area of every thermocouple and number of couple in the second stage
34
xiv
LIST OF SYMBOLS AND ABBREVIATIONS
I
Electrical current (A)
K
Thermal conductance of thermocouple (W/K)
A
Cross-sectional area of every thermocouple (cm2)
L
The length of thermocouple (cm2)
R
Electrical resistance of a thermocouple (Ω)
N
The number of thermocouple in second stage
qc
Heat flow rate of a thermocouples at the cold junction (W)
qh
Heat flow rate of a thermocouples at the hot junction (W)
QC
Cooling capacity of semiconductor thermoelectric module (W)
QH
Rejected heat flow of the thermoelectric module (W)
Α
Seeback coefficient (V/K)
α
Electrical resistivity (Ωcm)
k
Thermal conductivity (W/Kcm)
ε
Coefficient of performance
P
p-type semiconductor
n
n-type semiconductor
xv
LIST OF APPENDICES.
Title
Pages
APPENDIX A
39
APPENDIX B
43
1
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
A refrigerator is cooling appliance comprising of a thermally insulated compartment and a heat pump. These configurations allows respectively chemical and mechanical means of heat transfer from it to the external environment in order to cool the contents to that below ambient temperature. With the current technology development, there are many types of cooler used in refrigerator. Basically, refrigeration system can be divided into two types; compression
refrigerator
system
and
absorption
refrigerator
system.
Compression refrigerator, which is commonly used, normally make noticeable noise. The absorption refrigerator is different from compressor refrigerator. It operates based on the combustion of liquefied petroleum gas, solar thermal energy or an electric heating element. It is quieter than compressor motor in a typical refrigerator because it has no moving part.
Absorption refrigerator is also known as thermo-electric Peltier units which used quiet running is required; Peltier cooler are used in the smallest refrigerators as they have bulky mechanism. The thermoelectric coolers have been used widely in space, military, telecommunication and other applications
2 for cooling and stabilizing the devices temperature. Thermoelectric domestic heat pumps and air conditioners will become competitive in the world market. This is because energy costs and demands can only increase and environmental concerns can only increase. Also the environmental treaties have banned chlorofluorocarbons. Reduced manufacturing costs of thermoelectric devices have been opening up new markets.
Commercially available thermoelectric devices are very reliable when used as coolers and operated at temperatures below room temperature. Usually, thermoelectric coolers are used in cases where the cooling system design criteria includes such factors as high reliability, small size, low weight, intrinsic safety for hazardous electrical environments, and precise temperature control. A thermoelectric cooling system has an electric circuit including a direct current power source providing direct current through the electric circuit, a thermoelectric device has at least one heat sink and at least one heat source capable of being cooled to a predetermined temperature range, and a control assembly. The use of a thermoelectric device in a cooling system has conventionally followed the basic arrangement shown in Figure 1.1.
Figure 1.1. Conventional arrangement for thermoelectric cooler. Q1 is the heat to be pumped, P is the electrical power supplied. Q2 is the heat dissipated to the ambient.
3 Thermoelectric cooling systems are analogous to conventional refrigeration
systems.
A
thermoelectric
cooling
system
has
similar
subassemblies. However, thermoelectric cooling is specifically the abstraction of heat from electronic components by the Peltier effect. Potential uses range from the cooling of electronic components to domestic refrigerators and air conditioner for cooling/heating a room space as mention before.
Thermoelectric refrigeration is achieved when a direct current is passed through one or more pairs of n- and p-type semiconductor materials. Fig. 1.2 is a diagram of a single pair consisting of n- and p-type semiconductor materials. In the cooling mode, direct current passes from the n- to p-type semiconductor material. The temperature TC of the interconnecting conductor decreases and heat is absorbed from the environment. This heat absorption from the environment (cooling) occurs when electrons pass from a low energy level in the p-type material through the interconnecting conductor to a higher energy level in the n-type material. The absorbed heat is transferred through the semiconductor materials by electron transport to the other end of the junction TH and liberated as the electrons return to a lower energy level in the p-type material. This phenomenon is called the Peltier effect.
A second phenomenon is also important in thermoelectric refrigeration. When a temperature differential is established between the hot and cold ends of the semiconductor material, a voltage is generated. This voltage is called the Seebeck voltage, and it is directly proportional to the temperature differential. The constant of proportionality is referred to as the Seebeck coefficient.
4
Figure 1.2; Schematic of thermoelectric module operation (a) cooling mode; (b) heating mode.
5 1.2
PROBLEM STATEMENT
As known widely, compressor refrigerator is commonly use in large refrigerator and well known efficient than absorption refrigerator. Specify to thermoelectric refrigerator, it use in small size refrigerator, quiet running and very environmental friendly. However, it uses more electricity, poor coefficient performance and small cooling capacity. So in order to improve it, an investigation have been run in this project by considering the common semiconductor material in market, then investigate it parameter and may as one way to improve its effectiveness. In this project developed an analysis base on condition of the material such as it cross sectional area and number of thermocouple.
1.3
OBJECTIVES.
The objectives of the project are: i.
To model the thermoelectric cooler module to analysis it performance.
ii.
To analyze the cooling performance of thermoelectric cooler by changing the second stage current, area of thermocouple and number of thermocouple on second stage.
iii.
To know the optimize configuration of the 2 stage thermoelectric cooler based on parameter that investigated.
6 1.4
SCOPE OF PROJECT.
The scopes of the project are: i.
The performance of the thermoelectric will measure base on the value of coefficient of performance (COP) and the cooling capacity.
ii.
Then in order to determine all the performance, there are few parameter that will be measured during testing such as; cross sectional area (A), current varying in second stage (I), number of thermocouples (N) and other basic parameter such voltage.
iii.
Selecting the best semiconductor material that commonly use in market.
1.5 OUTLINE OF THE THESIS.
The thesis is divided into five chapters mainly. The first chapter discussed on the significant of the project. This includes the problem statement, objectives and the scope of the project. In Chapter 2, the literature review of the project stated. This chapter discussed the theory about thermoelectric module in detailed that support the introduction of this project from various sources. This is important to support why project should be done. Furthermore, there are some relevant fact and equation for this module stated.
In Chapter 3, methodology discuss on the project process which generally
divided
into
three,
mathematical
development,
software
implementation and analysis of data. In this chapter also shows step by step of each process were developing. The next Chapter 4, results and discussion were stated. Each of the data analysis discussed by separate it into 4 parts. There are discussion on the efficient size, effect of the current on second stage, effect of
7 the area of every thermocouple and the optimum configuration of thermoelectric module.
Lastly, Chapter 5 on conclusion and recommendations. In this chapter will conclude all the analysis with relevant fact and also recommendations stated for next studies.
8
CHAPTER 2
LITERATURE REVIEW
2.1 CHAPTER OVERVIEW.
As mention in previous chapter the introduction of absorption refrigerator- thermoelectric cooler general information, application and advantages. Then as state in problem statement section 1.2, the thermoelectric coolers need to improve it poor coefficient of performance and small cooling capacity. As one of the alternatives in solving this problem, in this project will develop some parameter such as cross sectional area and number of thermocouple. Generally the connection of thermoelectric cooler model as shown in figure 2.1.
9
DC source
semiconducto r material, n-type p-type
Conductor material
Figure 2.1 ; A real thermoelectric refrigerator cooler.
This chapter explains in detail about parameter that will consider in this project analysis that will affect the performance of thermoelectric based on several of source.
2.2 THERMOELECTRIC.
Currently, the one-stage semiconductor thermo-electric module is composed of a large number of thermocouples connected electrically in series and thermally in parallel. A thermocouple is made of a p-and a n-type semiconductor. A two-stage semiconductor thermoelectric module is stacked by one group of thermocouples on the top of the other, which is connected
10 thermally in series. In an actual operation, the working electric currents for them are in series or in parallel. Two types of two-stage thermoelectric coolers are both used in semiconductor thermoelectric refrigeration, and the types with separate electrical currents may have the best performance [1]. Therefore, the type of two-stage thermoelectric cooler with separate working electrical currents was selected as the model in this study. For simplicity, there is only one thermocouple in the second stage, but several thermocouples in the first stage for this module, as shown in Fig.1.1. In addition, a piece of thermally conductive but electrically insulating ceramic plate is placed between the first stage and the second stage.
2.2.1
PARAMETERS
As mention in objectives, by changing the current in second stage, area of thermocouple and number of thermocouple on second stage will affect the cooler performance, also mention by other researcher; that improvement of thermoelectric parameter that relate to thermocouple element and module are equally important in designing a high performance of thermoelectric cooler[1].
In semiconductor thermoelectric refrigeration, there are many factors influencing the performance of refrigeration such as thermoelectric materials, size of thermocouple and electrical current that supply to the circuit[2]. Before this an presented a method to improve the cooling capacity and coefficient of performance for two stage thermoelectric cooler based on the influences of the allocation of the junction temperature difference in the module and the length of thermocouple[2].
In this project also more emphasized on using of two-stage of thermoelectric modules because, it well known that two-stage semiconductor thermoelectric modules are often used for extending operation testing[3].In
11 addition, the performance of the coolers are not only depends on physical properties of the thermocouples, but also on the configuration of two-stage thermoelectric[4].Therefore, in this project will consider the area of thermocouple, current in second stage and number of thermocouples. Furthermore, in previous work, emphasized more on the effect of the length of the thermocouples but the effect of the area of thermocouple was not considered deeply.
In order to use material that will use in the project, it needs to identify its properties and capability. Most cooling unit are required to function in the region of room temperature [4] therefore, in this project use Bi2Te2-Bistmuth telluride which known as best material function in room temperature [5]. This general properties of material need to be consider as one of it specification that will be use later during analysis and as precaution. The general properties of material that will consider; specific heat of material- it high temperature and lowest temperature, it melting point, thermal expansion coefficient and others[5].The other material capability needs to consider are Seeback coefficient, electrical resistivity and thermal conductivity because refrigeration capability of semiconductor material is dependent of combined effect all above properties[6]. Since the scope of this project are not cover those parameter, so all of it will directly taking from manufacturer. Some of the information will use in calculation of performance by using c-programming later and the rest is for addition information.
Therefore, in this project the optimum configuration of a basic twostage semiconductor thermoelectric module was studied by investigating the current of the second stage, the area of thermocouple and the number of thermocouples. The analysing the effect of those parameters on cooling performance, the optimum performance relation obtained.
12 2.2.2
MATHEMATICAL EQUATIONS.
In order to figure out the performance of the thermoelectric cooler in this project need to carry out some equation that will involving during analysis. The cooling capacity of thermoelectric module is thus defined as 2 𝑞𝑐 = 𝛼2 − 𝛼1 𝐼𝑇𝑐 − 𝐼 𝑅 2 − 𝐾(𝑇𝐻 − 𝑇𝐶 )
(2.0)
Where the total electrical resistance of the branches in series is;
𝑅 =
𝑙1 𝐴 1 𝜎1
+
𝑙2 𝐴 2 𝜎2
(2.1)
And the total thermal conductance of the branches in parallel;
𝐾 =
𝐴1 𝑘 1 𝑙1
+
𝐴2 𝑘 2 𝑙2
(2.2)
The input power equation; 𝑤 = 𝛼2 − 𝛼1 𝐼 𝑇𝐻 − 𝑇𝐶 + 𝐼 2 𝑅
(2.3)
The total heat rejection equation; 𝑞ℎ = 𝑤 + 𝑞𝑐
(2.4)
And then coefficient of performance (COP);
∅=
𝑞𝑐 𝑤
(2.5)
Where,
qc= cooling capacity of semiconductor thermoelectric module (W) qh= rejected heat flow of the thermoelectric module (W). 𝛼 = seeback coefficient.
13 A = cross sectional area T = temperature of source and sink ( H and C) 𝑙 = length 𝜎 = electrical conductivity 𝑘 = thermal conductivity 𝐼 = current through the thermoelectric module (amp) [5],[1].
Figure 2.2 shows a simple model of thermoelectric structure where heat source side labelled as TC and heat sink side labelled as TH.
14
HEAT SOURCE Tc
I 2 1 + _ HEAT SINK TH Figure 2.2; Simple thermoelectric refrigerator.
From all the parameters of this project has been get from industry that produce the material. The electrical and thermal conductivity of material can be known by manufacturer that have running an experiment to test their product. As mention by K.H.Lee; the parameters such as temperature different, current, thickness of thermoelectric element, and the number of thermoelectric pairs will affect the performance [7].The thick element with larger number of thermoelectric pairs or the cross sectional areas of every element also improve the cooling performance [2],[4].
2.3 PERFORMANCE OF THERMOELECTRIC.
In this project the performance of thermoelectric cooler will measure by using analysis of coefficient of performance (COP) and its cooling capacity. As mention in previous 2.2.2 section, selection of material by considering their parameter, where parameters such as temperature different, current, thickness of thermoelectric element, and the number of thermoelectric pairs will affect the performance[7]. Known in equation COP and cooling capacity relate with all those parameter.
15 Normally, the coefficient of performance (COP) is the primary factor to evaluate the performance of the cooler [7] and it used to define the cooling “efficiency” where, the net heat absorbed at the cold end divided by applied electric power [6]. The analysis can be done by the COP varies with the parameters [1].
2.4
SUMMARY
The chapter has presented the parameter that considered in analysis performance of thermoelectric cooler and relevant equations that related to parameter which leading to measuring the performance of thermoelectric cooler. This is to be followed by discussion on methodology that had been used in this project in the next chapter
16
CHAPTER 3
METHODOLOGY.
3.1 CHAPTER OVERVIEW
This chapter will discuss about methodology that have been used to achieve the objective of the project. Overall, the project is divided into three parts, finding material data and properties, coding simulation and analysis.
17 Figure 3.1 show the flow chart of the project planning that has been developed in this project. Investigate equation
Investigate the relevant mathematical equation
Get the data and specification from industry
software
Running coding simulation-transform output into graph using M.O.Excel
analysis
Analysis all the output in term of performance
Figure 3.1; Planning
3.2 PROJECT PROCESS
Figure 3.1 shows the process of this project that separately into three parts, selecting mathematical equation, software and analysis.
18
3.2.1
MATHEMATICAL DEVELOPMENT.
In this project there are several equations that relate will be use which leading in gaining the coefficient of performance and cooling capacity. All the equation has been state in previous chapter. (2.2.2-mathematical equation)
The thermoelectric cooler for this project will design based on the real thermoelectric refrigerator cooler in Figure 3.2 The different on number of thermocouple/thermoelements in second stage while number of thermocouple in first stage will remain one pair only.
Figure 3.2; Schematic diagrams of multicouple thermoelectric modules. In this project also based on the concept where, for the first stage of thermocouple, the pumped heat rates at the cold side and rejected heat rates at the hot side can be express; 𝑞𝑐 and 𝑞ℎ similarly to the second stage. Then, in this project will used conventional analysis method for this thermoelectric module which not takes the effect of the thermal and contact resistance of both ceramic plates into consideration. By considering that a better thermal insulation is taken for the whole module, therefore the thermal resistances between two-stage and heat loss for the whole two-stage
19 thermoelectric module is neglected. Then following heat balance can be assumed;
Th2 = Tc1
(3.1)
qh2 = nqc1
(3.2)
Based on the equation, we can derive that cooling capacity at the cold side and the hot side of the whole two stage thermoelectric cooler are respectively as;
(3.3) (3.4)
Then coefficient of performance of two stage thermoelectric module is thus defined as; (3.5)
and current for second stage can be derived from equation which is written as; (3.6)
Using this set of equation, the module of thermoelectric the parameter will be test based on several of cross sectional area of the thermocouple element, number of thermocouple n and current I that varying.
The data and specification that obtained from manufacturer. MELCOR, USA state in appendix (B).There is 33 type of size and specification of material that use later.
20 3.2.2
SOFTWARE IMPLEMENTATION;
DESIGN OF CODING SIMULATION. All the data that get from manufacturer will be test using coding of mathematical equation that investigated. Generally, the coding is made in two sections. The first section in to determine the best size and the second section are to test all the parameter that consider as told before. Figure 3.3 show flow chart that represents the code.
Start.
Initialize data N=2 , I2=5.0A, α, λ, ρ ,TH, and TC
Calculate value K, R, I, Qc, Qh, and COP. no No operation
N
int main() { int n=0; double SUM, abselon, N=2.0, I2=5.0; double alfa=1.93e-4, lamda=1.9, ro=8.52e-6, Th=300, Tc=200; double K, R, I, Qc, Qh; double set[33][2]={ {.4,.5}, {.4,.8}, {.45,1.27}, {.5,.7}, {.5,1.0}, {.5,1.5}, {.52,1.6}, {.54,.76}, {.61,1.27}, {.61,1.52}, {.635,1.02}, {.65,1.0}, {.65,1.27}, {.81,1.27}, {.81,1.57}, {.85,.46}, {.85,1.27}, {.85,1.57}, {1.0,.46},
//[A][L]
41 {1.0,.64}, {1.0,1.27}, {1.0,1.3}, {1.0,1.57}, {1.0,1.65}, {1.0,2.03}, {1.2,1.4}, {1.2,1.91}, {1.36,.64}, {1.36,1.52}, {1.36,1.57}, {1.36,2.41}, {1.4,.4}, {1.4,.8}}; printf("SET 1\n\n");
printf("==A==============L========Abselon==========I=====\n");
do{ K=(2.0*lamda*pow(set[n][0]/1000.0,2))/set[n][1]; R=(2*ro*set[n][1])/pow(set[n][0]/1000.0,2); I=(alfa*Tc)/R; SUM = alfa*I*Tc - K*(Th-Tc); Qc = SUM - 0.5*I*I*R; Qh = SUM + 0.5*I*I*R; abselon = Qc/(Qh-Qc);
printf("%6.4e
%5.2lf
\n",pow(set[n][0]/1000.0,2),set[n][1],abselon,I); n++;
}while(n
