A Study on the Optimization of a PEM Fuel Cell with Open Cathodes 黃建彰、鄭錕燦
E-mail: 9608368@mail.dyu.edu.tw
ABSTRACT
In a PEM fuel cell stack with open cathodes air is forced to go through its cathode sides by an axial-fan, in which the air has a two-fold effect----being both a reactant gas and a coolant. This type of fuel cell system has a lot of merits, such as simple structure, compactness, and light-weight. So, they can be used as the power sources of small vehicles, such as electric wheel-chairs, scooters, and bikes. For a PEM fuel cell stack with open cathodes, the performance of the fuel cell depends on the quality of its membrane electrode assembly. Furthermore, the air channel size and air flow speed on the cathode side have substantial effect on the
temperature and performance of the stack. The present thesis focuses on this type of fuel cell stack. The temperature distribution and performance of the fuel cell under various channel designs and air flow speeds were investigated by numerical simulations using the commercial code COMSOL MULTIPHYSICS.
Keywords : PEM ; fuel cell ; Numerical simulation
Table of Contents
封面內頁 簽名頁 博碩士論文暨電子檔案上網授權書... iii 中文摘要... iv ABSTRACT... v 誌謝... vi 目錄... vii 圖目 錄... x 符號說明... xiii 第一章 緒論... 1 1.1前
言... 1 1.2燃料電池的介紹... 2 1.2.1燃料電池的原理... 2 1.2.2燃料電池的構 造... 4 1.2.3燃料電池的優點... 7 1.2.4燃料電池主要技術問題... 9 1.2.5燃料電池的性能 曲線... 9 1.3文獻回顧... 12 1.4研究動機及目的... 16 第二章 研究方
法... 18 2.1 COMSOL工程分析軟體簡介... 18 2.2有限元素法... 19 2.3數值模擬流 程... 20 2.4模型說明... 21 2.4.1氣體擴散層中之質傳模型... 21 2.4.2速度場、溫度 場與濃度場之計算模型... 23 2.5基本假設... 25 2.6統御方程式... 25 2.6.1氣體擴散層質 傳之統御方程式... 26 2.6.2速度分佈之統御方程式... 27 2.6.3溫度分佈之統御方程式... 27 2.6.4反 應物之濃度分佈之統御方程式... 28 2.7邊界條件... 29 2.7.1氣體擴散層質傳之邊界條件... 29 2.7.2速度分佈之邊界條件... 29 2.7.3溫度分佈之邊界條件... 30 2.7.4反應物濃度分佈之邊界條 件... 31 2.8格點分佈... 33 第三章 結果與討論... 36 3.1有效擴散係數之經驗方程式 驗證... 36 3.1.1氣體在擴散層內擴散的情形... 36 3.1.2彎曲係數之驗證... 38 3.2燃料電池溫度分 佈... 39 3.3反應物濃度分佈... 42 3.3.1氧氣質量分率在擴散層至流道間的分佈情形... 42 3.3.2水 氣質量分率在擴散層至流道間的分佈情形... 45 3.3.3不同入口流速對於氧氣、水氣質量分率及壓力變 化的影
響... 47 3.4燃料電池性能曲線... 49 第四章 結論及建議與未來研究方向... 53 4.1結 論... 53 4.2建議與未來研究方向... 54 參考文獻... 55
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