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研究生： 張哲維
Chang, Che-Wei
論文名稱： 交錯層狀磁致冷再生器之數值分析
Numerical Analysis of Active Magnetic Regenerators with Staggered Laminated Plates
指導教授： 許文震
Sheu, Wen-Jenn
口試委員: 陳炎洲
李隆正
學位類別： 碩士
Master
系所名稱： 工學院 - 動力機械工程學系
Department of Power Mechanical Engineering
論文出版年： 2020
畢業學年度： 108
語文別： 英文
論文頁數： 143
中文關鍵詞： 磁致冷卻 、磁熱材料 、磁致冷再生器
外文關鍵詞： Magnetic refrigeration, Magnetocaloric material (MCM), Active magnetic regenerator (AMR)
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    • 磁致冷卻利用磁熱材料的磁熱效應，取代傳統冷媒壓縮與膨脹過程，降低冷卻系統的成本，且無冷媒使用。以熱流觀點而言，磁致冷再生器存在兩個技術關鍵：(1)固態磁熱材料與流體間熱傳過程中的熱傳效率不佳，操作頻率無法增大；(2)冷熱端軸向之熱傳損失，熱量會經由熱傳導方式由熱端傳向冷端，降低磁致冷再生器的性能。
    不同於以往之平板設計，本研究將磁熱材料平板交錯置於冷卻系統中，奇數與偶數層斷點位置交錯。對相近的磁熱材料段而言，水平間中斷，相鄰兩層間差排。如此能增加熱端與冷端間磁熱材料熱傳導之熱阻，並增加徑向流，打破工作流體之邊界層，加強熱傳，以提升其操作頻率，進而增加磁致冷系統效能。
    本研究藉由商業軟體數值模擬，建立8種長為80 mm 之二維模型，分析新結構之磁致冷系統在不同操作狀態的表現。於磁場變化0-1特斯拉、冷熱端溫度283 - 303 K、循環週期0.6秒、利用因數0.4時， “4 right holes, 0.5 mm”較原模型減少磁熱材料使用2.5%與壓降減少4%，且製冷功率由62.48升至69.10瓦，散熱需求功率由129.13降至113.42瓦。本研究證實，透過交錯層狀磁致冷再生器之設計，能增加磁致冷裝置之效能。並透過溫度場分析，推論近熱端處仍可局部減少磁熱材料的使用。

    Magnetic refrigeration system, which functions without refrigerant consumption and compressor employment, is an ecofriendly novel refrigeration technology.
    However, two heat transfer problems restrict the efficiency of active magnetic regenerator (AMR). (a) Operation frequency could not be enhanced due to deficient heat flux between magnetocaloric material (MCM) and working fluid. (b) The heat conduction from hot side to cold one hinders the refrigeration capacity.
    The novel design which could increase the thermal resistance between the room temperature side and chilling temperature one and enhance the heat flux between two phases, was made. For a rectangular AMR plate, several rectangular staggered breaking points were employed instead of complete laminated plates. Breaking points of layers restricted the heat conduction effect from hot side to cold one. Furthermore, they brought secondary flow which broke boundary layers, and enhanced the heat convection effect.
    The commercial software was employed and 8 two-dimensional models with a length of 80 mm were created to analyze the performance of new AMRs at different operating parameters.
    Compared to the original model, "4 right holes, 0.5 mm" model reduces the usage of MCM by 2.5%, decreases the pressure drop of 4%, increases the cooling power from 62.48 to 69.10 watts, and reduces the heating power from 129.13 to 113.42 watts at the magnetic field changes of 0-1 Tesla, the temperature of the hot to cold ends of 283 - 303 K, the operation period of 0.6 seconds, and the utilization factor of about 0.4.
    This study shows that the performance of magnetic refrigeration devices can be intensified by active magnetic regenerators (AMRs) with staggered laminated plates, and it is inferred by temperature distribution that the MCM usage could be decreased locally.

    摘要 i Abstract ii 致謝 iv List of Illustrations vii List of Tables xiv Nomenclature xv Chapter 1. Introduction 1 1.1. Introduction 1 1.2. Background 2 Chapter 2. Theories and Literature Review 5 2.1. Magnetocaloric Effect (MCE) 5 2.1.1. Thermodynamic theory 5 2.1.2. Curie temperature (TCurie), First and Second Order Phase Transition 9 2.2. Magnetocaloric Material (MCM) 11 2.2.1. Gadolinium (釓, Gd) and Related Alloys 11 2.2.2. Manganese (錳, Mn) and Related Alloys 13 2.2.3. LaFe13-xSix and Related Alloys 16 2.2.4. Some of Other MCE Materials 17 2.3. Requirements and Some Designs of Magnetic Field Mechanisms 19 2.3.1. C-shaped Magnets 20 2.3.2. Halbach Array 21 2.4. AMR and AMRR 23 2.4.1. Active Magnetic Regenerator (AMR) 24 2.4.2. Active Magnetic Regenerator Refrigeration Cycle (AMRR Cycle) 25 2.5. Literature Review 26 2.5.1. AMR Apparatuses 26 2.5.2. Numerical Models of AMR System 42 Chapter 3. Numerical Methods 48 3.1. Problem Descriptions and Assumptions 48 3.1.1. Problem Descriptions and Proposed Solution 48 3.1.2. Physical Models of Numerical Model A, B, and C. 50 3.1.3. Assumptions 51 3.2. Modeling of AMR Cycles 52 3.2.1. Dimensions of Simulation Models 52 3.2.2. Time-Dependent Velocity and Magnetic Field 56 3.2.3. Governing Equations 59 3.2.4. Boundary and Initial Conditions 59 3.2.5. Material properties and Mean Field Theory (MFT) 65 3.2.6. Heat Convection Coefficient 71 3.3. Derived Values 72 3.3.1. Convergence Criteria 72 3.3.2. Performance Evaluation of AMR 73 3.4. Software Package Settings 74 3.4.1. Global Definitions (全域定義) 74 3.4.2. Component (元件) 74 3.4.3. Time-Dependent Simulation Solver 78 3.4.4. Relative Temperature Differences 79 3.4.5. Cooling/Heating Power 79 Chapter 4. Results and Discussion 80 4.1. Periodical Steady State 80 4.2. Verification and Differences between 1-D and 2-D Model A. 81 4.3. Cooling/Heating Power of Model B and C 88 4.3.1. Grid Independent Test 88 4.3.2. Cooling/Heating Power of Model B (Complete MCM Plates) 90 4.3.3. Cooling/Heating Power of Model C (Proposed Solution) 91 4.3.4. Specific Cooling/Heating Power of Model B and C 97 4.4. Comparison of Cooling/Heating Power between Potential Models 102 4.5. Qh-Qc and Qc/ (Qh-Qc) 108 4.6. Comparison of T(x) between Potential Models 115 4.7. Pressure Drops between Two Ends of AMRs 125 4.8. Flow Distribution with Staggered Breaking Points 127 4.9. Effect and Entrance Length with Staggered Breaking Points 130 4.9.1. Quick Test of Length of Breaking Points under Steady State 130 4.9.2. Flow Distribution Test under Transient State 132 Chapter 5. Conclusion and Prospect 135 5.1. Conclusion 135 5.2. Prospect 138 Reference 139 

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