A novel leaf bionic flow field with structured multi-level channel based on Murray's law in proton exchange membrane fuel cell for enhanced mass transfer

The design of flow field has a significant impact on the performance of proton exchange membrane fuel cells (PEMFCs). In this study, a novel leaf bionic flow field is designed and optimized based on Murray's law. The power consumption ratio is first used in the bionic PEMFC. Additionally, an evaluation criterion, the mass transfer efficiency evaluation criterion (MTEEC), is proposed to characterize mass transfer efficiency, and field synergy theory is used to analyze performance differences in mass transfer among various flow fields. The results demonstrate that adding multi-level channel and obstacles in the flow field significantly enhances cell output performance and reduces voltage losses in mass transfer regions. Applying Murray's law to distribute multi-level channel improves the uniformity of oxygen concentration distribution in the flow field and alleviates under-rib water accumulation. Compared to the secondary stream flow field (SSFF), the structure mesh of leaf bionic flow field (SMLBFF) demonstrates a nearly 19% increase in current density output at 0.45 V. SMLBFF exhibits an 81.51% increase in convective mass transfer rate compared to SSFF at 0.4 V. Moreover, the MTEEC of SMLBFF shows improvements of 179.68% at 0.5 A/cm2 and 135.43% at 1.0 A/cm2, compared to SSFF.