這是熱虹吸實驗，研究的目的主要是研究熱回收和節能，因為它廣泛的應用於商業工程設備。熱管和虹吸管是使傳熱系統效率最大化的關鍵技術。本論文的初步研究以水和Dowtherm-A為工作流體的熱虹吸管的熱性能。初步實驗結果用於評估熱阻和有效熱傳導。實驗結果以圖形的形式進一步比較以獲得最低的熱阻和最高的熱傳導率。最大熱容測試的結果用於繪製圖表。此Dowtherm-A熱虹吸管之工作溫度為250度。此外，利用Payakaruk等人所開發的理論相關性，在理論上和實驗上比較了90度的最低熱阻。對不同配置之參數的溫度和時間圖進行觀察，以找出給定條件下的啟動溫度。

The purpose of this experimental study on thermosyphon is mostly because of the interest in studying heat recovery and energy saving as it finds application in a huge range of commercial engineering devices. Heat pipes and thermosyphon are the key technologies to maximize the efficiency of a heat transfer system .The preliminary study in this paper is to investigate the thermal performance of water and Dowtherm-A thermosyphons. The dimensions of all the considered thermosyphons were same i.e. 915mm by length and 12.7 mm outer diameter with 0.5 mm wall thickness. The preliminary experimental results are used to evaluate the thermal resistance and effective thermal conductivity. The results are further used to compare in the form of graphs to obtain the lowest thermal resistance and highest effective thermal conductivity. Maximum heat capacity tests on water thermosyphons are carried and graphical results are plotted.  Further, mathematical correlation developed by Payakaruk et al is used to compare the minimum thermal resistance against experimentally obtained data at 90° inclination. The temperature versus time graph for different configurations and parameters are observed to find out the startup temperature in a given set of condition.

Chinese Abstract………………………………………………………………….I
Abstract………………………………………………………………………......II
Acknowledgements………………………………………………………………IV
Nomenclature…………………………………………………………………….V
Table of Contents……………………………………………………………VII
List of Figures…………………………………………………………………XII
List of Tables………………………………………………………………….XVI
Chapter 1 Introduction…………………………………………………………...1
1.1	Literature and Motivation……………………………………………..1
1.2	General Background……………………………………………………4
1.3	Dowtherm-A :Health and Environmental Considerations…………8
1.4	Physical Properties of Dowtherm A and Water……………….......9
1.5	Aim of the Research…………………………………………………..13
Chapter 2 Heat Pipes and Thermosyphons………………………………......14
   2.1   Two-Phase Closed-Thermosyphon Operation Principle………......14
   2.2    Heat Transfer Limitation of a Thermosyphon……………………..16
 2.2.1 Dry-out Limit…………………………………………………...16
2.2.2 Boiling Limit…………………………………………..….16
2.2.3 Flooding Limit………………….……………..…..………..…..17
   2.3    Heat Transfer Limitation of a Heat pipe………………..………….17
 2.3.1 Viscous Limit…………………………………………........18
 2.3.2 Sonic Limit………....………………..…………..………………....19
2.3.3 Entrainment Limit…………………………………………20
2.3.4 Boiling Limit………………………………………….........20
 2.3.5 Circulation Limit……………………………………........20
2.4 Thermal Resistance ………………………………………………..21
2.5 Thermosyphon Thermal Resistance Network…………………. 21
2.6 Heat Pipe Thermal Resistance Network………………………...24
2.7 Wicks and Types of Wicks………………………………………..25
2.8 Thermosyphon and Heat Pipe Applications……………….......27
2.9 Figure of Merit of Dowtherm-A………………………………….31
Chapter 3 Apparatus and Procedure……………………………………..... ……….33
3.1Experimental Setup…………………………………………... ………………………..33
   3.2 Thermosyphon Dimensions and Thermocouple positions……...34
3.2.1 Location of Thermocouples and Temperature measurement. ….35
3.2.2 Evaporator section………………………………………..... ………………………40
3.2.3 Condenser section……………………………………………...... ………………..40
   3.3 Specifications of Thermosyphons……………………………...... ………41
   3.4 Experimentation Procedure…………………………………....... …………45
   3.5 Data Analyzing Procedure…………………………………..... ………………46
3.5.1 Minimum Thermal Resistance at Heat Input Flux……....…………….47
Chapter 4 Experimental Results………………………………………....... …………48
4.1 Test Overview for Water Thermosyphon…………………....... ……………48
4.1.1 Filling ratio 18.5% Water Thermosyphon…………………...... ………….48
4.1.2 Filling ratio 18.9% Water Thermosyphon…….………............. ……….53
4.1.3 Filling ratio 19.5% Water Thermosyphon……….…………...... ………..57
4.1.4 Axial Position versus Temperature along the axis …............ ………62
 
4.1.5 Thermal resistance versus Input Heat Flux……………….. ……………..63
4.1.6 Effective Thermal Conductivity versus Input Heat Flux……………..64
4.1.7 Comparison of thermal resistances………………………….. …………….66
4.1.8 Energy Balance………………………………………………... …………………….68
4.2 Test Overview for Dowtherm-A Thermosyphon…………………. ………69
4.2.1 Filling ratio 14.9% Dowtherm-A Thermosyphon……………………….70
 4.2.2 Filling ratio 15.5% Dowtherm-A Thermosyphon…………. ………...72
4.2.3 Axial Position versus Temperature along the axis………………………75
 4.2.4 Effective Thermal Conductivity versus Input Heat Flux…. ……….76
 4.2.5 Thermal resistance versus Input Heat Flux………………………………77
4.2.6 Comparison of thermal resistances………………………….. ……………..78
4.2.7 Energy Balance………………………………………………………………………….80
Chapter 5 Summary…………………………………………………….. ……………………82
5.1 Conclusions…………………………………………………………. ……………………...82
5.1.1 Water Thermosyphon Conclusions……………………….... ………………..82
5.1.2 Dowtherm-Thermosyphon Conclusions……………………. ………………84

 

5.2 Recommendations for future work………………………………………………85
References……................................................................................. ……87
APPENDIX I…………………………………………………………………………………………90
APPENDIX II……………………………………………………………. …………………………92

List of Figures
Figure 1.1 Schematic of a heat pipe showing the components and the principle of operation………………………………………………………….5
Figure 2.1 Thermosyphon Schematic Working Mechanism………………14
Figure 2.2 Heat Pipe Limitations…………………………………………....18
Figure 2.3 Distribution of Vapor Pressure along the Heat Pipe…………19
Figure 2.4 Thermosyphon Thermal Resistance Network………………….22
Figure 2.5 Thermal Resistances in a Heat Pipe………………….………...24
Figure 2.6 Major Wick Structures…………………………………….……..26
Figure 2.7 Heat Pipe Heat Exchanger for Heat Recovery…………….….28
Figure 2.8 Steam Pipes Deck Oven………………………………………….29
Figure 2.9 Heat Pipe Cooling System for Electronic components……….29
Figure 2.10 Thermosyphon for Solar Desalination System……………….30
Figure 2.11 Temperature Response of FOM Values……………………....32
Figure 3.1 Schematic of Experimental Setup………………………...…….33
Figure 3.2 Schematic of the thermosyphon with thermocouple locations……………………………………………………………………........ 34
Figure 3.3 Tested Thermosyphons…………………………………………...36
Figure 3.4 K-type Thermocouples used in the Experiment………………36
Figure 3.5 Insulations used in Evaporator and Condenser……………….37
Figure 3.6 Adiabatic Insulation used in Experiment……………………………37
Figure 3.7 Thermostat Reservoir…………………………………………. …………..38
Figure 3.8 AC Power Supply…………………………………………….... …………….39
Figure 3.9 Experimental Setup……………………………………………. ……………39
Figure 4.1 Temperature response (160W, 60°, FR-18.5%)…………………..49
Figure 4.2 Temperature response (160W, 90°, FR-18.5%)…………………..49
Figure 4.3 Temperature response (200W, 60°, FR-18.5%)……………..……50
Figure 4.4 Temperature response (200W, 90°, FR-18.5%)……………….. ..50
Figure 4.5 Temperature response (240W, 60°, FR-18.5%)………………. ...51
Figure 4.6 Temperature response (240W, 90°, FR-18.5%)……………..……51
Figure 4.7 Maximum Heat Capacity Test (FR-18.5%)…………………. ………52
Figure 4.8 Temperature response (160W, 60°, FR-18.9%)……………….. …53
Figure 4.9 Temperature response (160W, 90°, FR-18.9%)………………. ….54
Figure 4.10 Temperature response (200W, 60°, FR-18.9%)…………………54
Figure 4.11 Temperature response (200W, 90°, FR-18.9%)…………………55
Figure 4.12 Temperature response (240W, 60°, FR-18.9%)…………………55
Figure 4.13 Temperature response (240W, 90°, FR-18.9%)…………………56
Figure 4.14 Maximum Heat Capacity Test (FR-18.9%)……………….. ………56
Figure 4.15 Temperature response (160W, 60°, FR-19.5%)……………... ..58
Figure 4.16 Temperature response (160W, 90°, FR-19.5%)……………... …58
Figure 4.17 Temperature response (200W, 60°, FR-19.5%)……………... …59
Figure 4.18 Temperature response (200W, 90°, FR-19.5%)……………... …59
Figure 4.19 Temperature response (240W, 60°, FR-19.5%)……………... ..60
Figure 4.20 Temperature response (240W, 90°, FR-19.5%)……………... ..60
Figure 4.21 Maximum Heat Capacity Test (FR-19.5%)……………….. ………61
Figure4.22 Temperature Profile along the length of the Thermosyphon 
at Different Power Inputs for Water Thermosyphons………………..... ……62
Figure4.23 Comparison of Thermal Resistance versus Heat Input Flux………………………………………………………………………….. ………………………63
Figure4.24 Comparison of Effective Thermal Conductivity versus Heat Input Flux………………………………………………………………….. …………………….64
Figure4.25 Comparison of the Theoretical Thermal Resistance against Experimental Thermal Resistance at Specific Power Input…………... …..66
Figure 4.26 Energy Balance at Constant Power Input………………... ……..68
Figure 4.27 Temperature response (160W, 90°,FR-14.9%, Inlet Temperature 80°C)……………………………………………………………………...... …70
Figure 4.28 Temperature response (200W,90°,FR-14.9%, Inlet Temperature 80°C)……………………………………………………………………….. ….71
Figure 4.29 Temperature response (210W,90°,FR-14.9%, Inlet Temperature 90°C)……………………………………………………………………….. ….71







Figure 4.30 Temperature response (160W, 90°,FR-15.5%, Inlet Temperature 80°C)………………………………………………………………………. …73
Figure 4.31 Temperature response (200W,90°,FR-15.5%, Inlet Temperature 80°C)……………………………………………………………………….. ..73
Figure 4.32 Temperature response (210W,90°,FR-15.5%, Inlet Temperature 90°C)……………………………………………………………………….. …74
Figure 4.33 Temperature Profile along the length of the Thermosyphon at Different Power Inputs for Dowtherm-A Thermosyphons……………75
Figure 4.34 Comparison of Effective Thermal Conductivity versus Heat Input Flux…………………………………………………………………. ……………………76
Figure 4.35 Comparison of Thermal Resistance versus Heat Input Flux…………………………………………………………………………………………………77
Figure 4.36 Comparison of the Theoretical Thermal Resistance against Experimental Thermal Resistance at Specific Power Input………….. …78
Figure 4.37 Energy Balance at Constant Power Input………………. …….80

List of Tables
Table 1-1 Intermediate Temperature Range Fluids……………………...3
Table 1-2 Properties of Dowtherm-A and Water………………………..10
Table 1-3 Saturated Liquid Properties of Dowtherm-A (SI Units)……12
Table 2-1 List of Resistances Formulas involved with Figure 2.4……..23
Table 2-2 Wick Structure Comparison………………………………...….26
Table 2-3 FOM Data Plotted in Figure 2.11 …………………………….31
Table 3-1 Dowtherm-A Thermosyphon Specification (FR 14.9%)…….42
Table 3-2 Dowtherm-A Thermosyphon Specification (FR 15.5%) ……42
Table 3-3 Water Thermosyphon Specification (FR 18.5%) ……………43
Table 3-4 Water Thermosyphon Specification (FR 18.9%) …………....43
Table 3-5 Water Thermosyphon Specification (FR 19.5%) ……………44
Table 4-1 Thermal Resistance Data Plotted in Figure 4.23……………63
Table 4-2 Effective Thermal Conductivity Plotted in Figure 4.24……65
Table 4-3(a)FR 18.5% Data Plotted in Figure 4.25 …………………....66
Table 4-3(b)FR 18.9% Data Plotted in Figure 4.25 ……………………67



Table 4-3(a)FR 19.5% Data Plotted in Figure 4.25 ……………………67
Table 4-4 Effective Thermal Conductivity Plotted in Figure 4.34……76
Table 4-5 Thermal Resistance Data Plotted in Figure 4.35…………...77
Table 4-6(a)FR 14.9% Data Plotted in Figure 4.36 ……………………79
Table 4-6(b)FR 15.5% Data Plotted in Figure 4.36 ……………….…..79
Table I(a) Experimental Data for 18.5% filling ratio water…………….90
Table I(b) Experimental Data for 18.9% filling ratio water…………….90
Table I(c) Experimental Data for 19.5% filling ratio water……………91
Table II(a) Experimental Data for 14.9% filling ratio Dowtherm-A….92
Table II(a) Experimental Data for 14.9% filling ratio Dowtherm-A….92

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