Study on mass transfer enhancement of locally improved structures and the application in serpentine and parallel flow fields of PEM fuel cells

Oxygen transport and water management within proton exchange membrane (PEM) fuel cells can be enhanced by locally improved structures in the flow field. Structures such as the new variable diameter structure and the block structure can significantly improve the PEM performance. In this paper, a three-dimensional numerical model is established to compare different types of locally improved structures. The structures, which employed the same compression volume, consist of a block structure, long block structure, and the new variable diameter structure. The mass transfer characteristics and the optimal layout of the locally improved structures are studied. Then, the new variable diameter structure and the block structure are incorporated into the serpentine flow field (SFF) and the parallel flow field (PFF) to form new flow fields, and their effects on the SFF and PFF are analyzed. The new variable diameter structure improves the uniformity of oxygen, and the block structure enhances the local mass transfer. The presence of the locally improved structure in the middle of the FF gives the best performance. In addition, the improved SFF has very limited performance and poor water management, but the oxygen distribution in the variable diameter PFF (PFF@VD) was significantly improved, and the peak power was increased by 26%. The energy consumption caused by pressure drop (ECP) is adopted to evaluate the performance of the flow field with locally improved structures; the PFF@VD has a higher proportion of net output power compared to the unmodified PFF.