Numerical analysis of parallel flow fields improved by micro-distributor in proton exchange membrane fuel cells

Abstract

The flow field on bipolar plates of proton exchange membrane fuel cells (PEMFCs) is critical to flow distribution and overall pressure drop, both of which have great influence on cell performance. A micro-distributor was proposed to improve the uniformity of flow distribution in parallel flow field. The effects of micro-distributor size on output cell performance and pressure drop were systematically studied with computational fluid dynamics (CFD) simulations. To evaluate the competence of the modified parallel flow field, a serpentine flow field was also considered for comparison. The results suggest that the modification of the flow field is able to enhance the uniformity of flow distribution significantly. The maximum output power density increases when decreasing the size of micro-distributor. Compared with the serpentine flow field, the modified parallel flow field with micro-distributor enables the fuel cell to give nearly comparable output performance, but requires two orders of magnitude lower pressure. More generally, it was found that the flow uniformity could be simply and conveniently improved by enhancing the mean pressure drop in the sub-channels. The origin of non-uniform distribution of oxygen concentration in the interface of gas diffusion layer (GDL) and catalyst layer (CL) was also discussed. This work provides an alternative to conventional parallel and serpentine flow fields, and is helpful for the designing of high output PEMFCs.