質子交換薄膜燃料電池氣體流道內質量傳遞之研究

A Study of Transport Phenomena for the Gas Channel in the Proton-Exchange-Membrane Fuel Cells

徐昌志(Chuan-Ji She)

指導教授 ： 蔡瑞益

中原大學/工學院/機械工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200260

摘要

摘 要

燃料電池為未來極具有潛力的能源之一，而提昇其功率密度也是目前極欲突破的目標；然而陰極氣體流道中，液態水的產生將會阻礙氧化劑擴散至陰極。本研究的目的在研究質子交換薄膜(PEM)燃料電池流道中流體的傳輸現象與其產生的效應。研究將藉由改變流體的輸入流率與電池的操作溫度，來增加工作流體在流道內的分壓以及水蒸氣的挾帶能力，以延後液態水凝結的位置並減少液態水產生的量，藉以提高燃料電池的效率。同時，工作流體輸入流率增加，僅需加入一些額外的功即可克服。研究之目的乃找尋最佳化之運作條件，以作燃料電池設計與分析。
研究中以MATLAB程式語言來撰寫模擬燃料電池陰陽兩極流道內之濃度分布與質子交換薄膜之水分傳遞情形。而模型乃沿著流道方向作計算，並考慮流道中燃料與氧化劑之消耗率。模擬結果顯示：(1) 當陰極中水蒸氣的分壓超過飽和蒸氣壓時，水蒸氣就會開始凝結產生液態水。此時由氧氣消耗反應得到的水分以及來自陽極的水分還會繼續增加，使得液態水的產量也會跟著增加。(2)運作的平均電流密度愈高，陰極渠道內的水蒸氣的流率以及液態水的產量愈大。(3) 增大陰極渠道工作流體之流率或者增高電池操作溫度，除了能夠延後飽和狀態發生的位置，同時有助於減少液態水的產生量。

關鍵字

平均電流密度 ； 功率密度 ； 氣體流道 ； PEM燃料電池

並列摘要

ABSTRACT

Fuel cell is the next-generation electric power. How to increase its performance has gained importance in the future. Water management is critical for achieving high performance of proton exchange membrane (PEM) fuel cells. The purpose of this proposal is to study the phenomena and effects of the working fluid transport in the cathode and anode channel. By changing the entering gas flow rate and the operating temperature of the fuel cell, which would increase the partial pressures of working fluid and increase the carried capacity of water vapor, can delay the condensation position and reduce the liquid water generation in the gas channel. At the same time, we only have to supply some additional work for increasing the entering gas flow rate. The better operation condition is helpful for the design of PEM fuel cells.
MATLAB programs is employed to simulate the distribution of species in the gas channel and water transport across the membrane. Calculations are done along the gas channels, and the consuming rate of oxidant and hydrogen are also considered. Results from the model have showed that：(1) When the partial pressure of water vapor is more than the pressure of the saturated water vapor in the cathode channel, water vapor will start to condensate to generate liquid water. Then the water from consuming oxidant and the transport of the anode will sequentially increase, which may cause the increasing of liquid water. (2) At high average current density, the water vapor flow rate and the generation of liquid water in the cathode channel are higher than these at low average current density. (3) The increase of the entering gas flow rate and the operating temperature in the fuel cell can delay the condensation position and reduce the liquid water generation in the gas channel.

並列關鍵字

average current density ； power density ； gas channel ； PEM fuel cells

參考文獻

【1】C.L. Marr, “Performance Modeling of a Proton Exchange Membrane Fuel Cell”, Masters Thesis, Department of Mechanical Engineering, University of Victoria, Canada, 1996.

【2】J.J. Baschuk and Xianguo Li, “Modeling of polymer electrolyte membrane fuel cells with variable degree of water flooding”, Journal of Power Source 86 (2000), 181-196.

【5】J. Kim, S. Lee, and S. Srinivasan, “Modeling of proton exchange membrane fuel cell performance with an empirical equation”, J. Electrochem. Soc. 142 (8) (1995), 2670-2674.

【6】J.C. Amphlett, R.M. Baumert, B.A. Peppley, and P.R. Roberge, “Performance modeling of the Ballard Mark Ⅳ solid polymer electrolyte fuel cell Ⅰ： mechanistic model develop”, J. Electrochem. Soc. 142 (1) (1995), 1-8.

【7】D.M. Bernardi and M.W. Verbrugge, “A mathematical model of a solid polymer electrolyte fuel cell”, J. Electrochem. Soc. 139 (9) (1992), 2477-2491.