Numerical study of subfreezing temperature cold start of proton exchange membrane fuel cells with zigzag-channeled flow field

Abstract

Abstract An automotive proton exchange membrane fuel cell (PEMFC) engine needs to be capable of surviving from sub-freezing temperatures. Cold starting up a PEMFC engine presents great technical challenge due mainly to the intra-electrode ice formation that is closely related to the involved multi-physical transport. The flow field configuration to some extent dictates the reactants and product transport and is thus of important influence on PEMFC cold start performance. The present work carefully analyzes the cold start process of PEMFCs with zigzag-channeled flow field (ZZFF). A transient three-dimensional numerical model is established and experimentally validated first, and then we make comparisons of cold-start performance between zigzag and straight channel flow-field PEMFCs to reveal the effects of ZZFF. It is found that the ZZFF better distributes the reactants/product and current density in the PEMFC as it enhances the transport along the flow direction in-between the under-land and under-channel regions inside the cell. The process of cold starting the ZZFF PEMFC is found to generate slightly less heat, which is not good to cold start. Therefore, the ZZFF enhances the survivability of PEMFC engine cold starting from subfreezing temperatures, whereas it slightly degrades the quick self-startup ability of PEMFC engine. Case study with PEMFCs of more zigzagged flow fields further corroborates the effects of ZZFF configuration on PEMFC cold start performance.