Evaluation of performance and mass transfer characteristics by applying oblique fin flow field to air-cooled PEMFCs under different ambient conditions

The choice of a suitable cathode flow field under varying ambient conditions (humidity and temperature) is essential for restraining mass transfer resistance and preventing localized overheating in air-cooled proton exchange membrane fuel cells (PEMFCs). To achieve this objective, this study recommends adopting a modified design that integrates tapered oblique fin (OF) channels into the ribs of the conventional parallel flow field. Subsequently, the superiorities of the modified design in terms of mass transfer capabilities and performance improvements under various ambient conditions are assessed compared to the conventional design through numerical analysis. The results show significant enhancements in mass transfer and cell performance with the modified design at higher humidity levels (e.g., 60 %-90 %). Besides, the modified design also achieves better performance in low air temperatures (e.g., 281.15 K-302.15 K). At an air temperature of 281.15 K, a maximum performance improvement of 9.34 % can be obtained. Air temperature and humidity both non-linearly affect current density distribution uniformity in the cathode CL. This is attributed to the complex interplay between water accumulation and oxygen transport under the ribs, coupled with convection phenomena within the OF channels. Moreover, the modified design more effectively enhances the temperature uniformity within porous electrodes at lower air temperatures.