STUDY OF THERMAL MANAGEMENT IN PEM FUEL CELLS WITH NUMERICAL MODELING AND IN SITU DIAGNOSIS APPROACHES

Thermal management is one of the major technical challenges to the commercialization of proton exchange membrane (PEM) fuel cells. Various aspects of thermal management, including the process of heat generation and heat transfer as well as cooling methods are introduced and discussed. Numerical modeling and in situ diagnosis are used to promote fundamental understanding of the heat generation, heat transfer and mass transfer as well as other issues in PEM fuel cells. Two improved mathematical models have been developed. The modeling results of temperature distribution and liquid water distribution are presented and discussed, demonstrating the values of numerical modeling in obtaining detailed information of heat generation, heat transfer and mass transfer. Two in situ diagnostic techniques, one for temperature distribution and the other for current distribution, have been developed. The phenomena of serious flooding was observed and investigated with in situ measurement of temperature distributions. It is found that flooding can occur very quickly and cause very serious decrease of performance, which greatly influence the heat generation and heat transfer process. Current distributions in PEM fuel cell with interdigitated flow fields and serpentine flow fields were investigated and compared using the in situ current distribution measurement technique. Measurement results show that flow fields structure has significant influence on local performance as well as heat and mass transfer, due to the different transport mechanisms with different flow fields. Simultaneous measurement and correlation of temperature distribution and current distribution demonstrates not only the great dependence of local heat generation on local current density but also the variation of heat generation from irreversibility of the electrochemical reactions. Based on the results and discussion, further research efforts in this field are also prospected.