Effect of inlet–outlet manifold configuration on reactant distribution and performance of pin-type flow fields in PEM fuel cells

The bipolar plate flow field is a critical component governing proton exchange membrane fuel cell (PEMFC) performance because it directly controls reactant delivery, heat removal, and pressure losses associated with parasitic pumping power. This study numerically investigates the influence of inlet–outlet manifold configurations on the transport behavior and electrochemical performance of a PEMFC employing a pin-type flow field. Eight different configurations, namely U-type, Z-type, L-type, Double L-type, Y-type, Reverse Y-type, T-type, and Reverse T-type, were analyzed under identical operating conditions to isolate the effect of manifold architecture. A three-dimensional, steady-state, single-phase computational model was developed to examine pressure distribution, reactant mass fraction fields, temperature distribution, and polarization characteristics within the cell. The results indicate that the inlet–outlet arrangement significantly affects the internal pressure gradients and reactant transport pathways across the flow field. Configurations that promote distributed flow patterns provide more uniform hydrogen and oxygen availability at the catalyst layer and improve thermal uniformity within the membrane–electrode assembly. Among the investigated cases, the Y-type configuration exhibited the best electrochemical performance, achieving a current density of 1.23 A/cm2 at 0.4 V and a maximum power density of 0.493 W/cm2. These values correspond to improvements of approximately 24.4% and 22.3%, respectively, compared with the conventional U-type configuration. Overall, the findings demonstrate that optimizing the inlet–outlet manifold architecture is an effective strategy for improving reactant utilization and enhancing the overall performance of pin-type flow field PEMFCs without modifying the internal pin geometry.