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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/2770

    Title: 質子交換膜燃料電池陰極端之兩相流模擬與研究
    Authors: 江彥德;Yen-Te Chiang
    Contributors: 機械工程研究所
    Keywords: 兩相流;質子交換膜燃料電池;水管理;two phase flow;water management;PEMFC
    Date: 2005-06-28
    Issue Date: 2009-09-21 11:55:23 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本文主要藉由兩相流理論,建立PEMFC燃料電池二維、定常及等溫的單電池模型,討論陰極支撐層(Backing layer:包含氣體擴散層與微孔層)及催化層兩部分建立其數學模型及邊界條件,來探討不同區域下所產生的源項和改變操作及性能參數的影響。 陰極支撐層是以多成分模式來考慮,主要成分有氮氣、氧氣、水氣與生成液態水,探討氧氣、水氣與生成液態水在多孔介質中的分佈。支撐層中的微孔層是一層有細緻孔洞的多孔介質薄層,藉由微孔層的細緻孔洞,將催化層所產生的液態水細化成小水珠以利於排除。本文中,藉由兩相流模型與理論,考慮氣體擴散層與微孔層之孔隙率及不同厚度條件下,對液態水生成情況與電池性能的影響。 催化層的探討部分,主要是探討電化學反應中氧氣與氫離子的傳遞和反應現象產生的電流、電位與生成液態水的分佈情形,電化學反應是使用Bulter-Volmer方程式來描述,質子交換膜中氫離子通量是使用Nernst-Planck方程式來描述。在催化層中,考慮氫離子在電解質中的含量與擴散係數,探討對液態水的生成以及電池性能的影響。 Until now, water management is an important issue on the performance of proton exchange membrane fuel cells (PEMFC). Especially, at high cell load or low gas flow rate, the two-phase transport of reactants and products constitutes an important limit in performance of PEMFC. In the two-phase region, product water obstructs the open pores of the cathode gas diffusion layer (GDL) and micro-porous layer (MPL) and limits the reactants transport to the active catalyst sites. In this study, we establish the two-dimensional, steady state, isothermal two-phase model according to two-phase theory. The occurrence of liquid saturation in what sites of GDL, MPL and catalyst layer can be anticipated in this model. Via this two-phase model, we discuss the effect on PEMFC performance and liquid saturation with different porosity and thickness of GDL and MPL. In another way, we study the proton behavior and the influence on current density, liquid saturation distribution in catalyst layer via this two-phase model、Bulter-Volmer equation and Nernst-Planck equation. Result shows that by increasing the porosity of porous medium, increasing the cell performance due to enhance the reactants transport and render them more active for electrochemical reaction surface. When the proton exchange membrane can hold more protons in unit volume and increase proton diffusion coefficient in the electrolyte, the PEMFC performance will be increased.
    Appears in Collections:[機械工程研究所] 博碩士論文

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