多孔材應用於質子交換膜燃料電池散熱之研究;Application of porous medium in PEM fuel cell cooling system

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题名:	多孔材應用於質子交換膜燃料電池散熱之研究;Application of porous medium in PEM fuel cell cooling system
作者:	林亭君;Ting-chun Lin
贡献者:	能源工程研究所
关键词:	質子交換膜燃料電池;散熱流道;金屬發泡材;氣冷;電池堆;air cooling;PEMFC;metal foam;stack;cooling plate
日期:	2012-01-31
上传时间:	2012-06-15 19:36:58 (UTC+8)
摘要:	質子交換膜燃料電池之最終產物除了水與電外，也會產生熱。隨著燃料電池技術日漸成熟，電池堆也跟著發展起來。為了保持低溫操作條件(<80 。C)，必須對電池進行冷卻動作。本文採取氣冷方式散熱，優點是可避免水冷散熱會產生離子導電的問題。另外，金屬發泡材具有重量輕、導熱佳及增加熱傳表面積等優點。本論文為首篇將金屬發泡材應用至燃料電池散熱系統之研究。本研究先製作幾種傳統散熱流道，並與有使用發泡材的散熱流道做比較，測量每種設計的熱對流係數並建立經驗關係式，了解各種流道的散熱能力，接著進行電池堆的實際成效量測。由實驗結果可以得知，在一樣大小的設計面積下，由於受到空間上的限制，若使用傳統方式將肋條作為分隔流場與流道設計的主軸，不但不易達到流場均勻，也無法有效增加熱交換表面積，造成傳統流道的散熱效果低落。實驗結果也顯示，若填充發泡材在散熱流道中，因為發泡材的多孔特性，能使熱壁與冷卻氣體做熱交換的表面積增加，氣體在散熱裝置內部流動的路徑會變長，可有效利用冷卻氣體。此外，雖然發泡材流道的壓降比傳統流道大，但是因為經過計算結果得知在整體效率上，使用發泡材流道會比傳統流道來的高效率，因此建議在散熱用流道額外使用發泡材。Except water and power, proton exchange membrane fuel cell (PEMFC) also generates heat while it is on operating. In order to keep PEMFC working in low temperature condition (<80 。C), it is required to develop a cooling system to remove waste heat. This study is focused on air cooling method, because it has the advantage of avoiding ionic contamination problem in liquid cooling method. Moreover, metal foam is lightweight, has high thermal conductivity, and large surface area for heat exchange. This study is the first investigation on metal foam applied to PEMFC cooling system. In this study, the cooling ability of the plate designs in metal foam cooling channel and traditional cooling channels, including column channel and serpentine channel, are compared. Via measuring heat transfer coefficient, the correlation between Nu and Re is established empirically. These cooling designs are also applied to a 4-cell stack to verify the cooling effect. The results show that the cooling ability of traditional cooling design is relatively poor due to the non-uniformity of gas flow, and the surface area for heat exchange is difficult to be increased in the traditional cooling design. On the contrary, the metal foam cooling design is better than the traditional ones. With the larger effective surface area and the ability to force a uniform gas flow, the heat transfer coefficient on metal foam design is larger than that of the traditional design, and it leads to that more heat could be taken away by the metal foam cooling design in a limited heating area. The pressure drop is larger in the metal foam design due to the drag caused by the porous structure, thus it needs extra pump work. However, the overall efficiency is still higher on system using metal foam cooling design than using traditional design. Thus it is recommended using metal foam design in a PEMFC stack system.
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