Transport enhancement–hydraulic resistance trade-offs induced by hemispherical baffles in proton exchange membrane fuel-cell channels

Geometric disturbances within confined flow passages play an important role in regulating the coupled transport and hydraulic behavior of proton exchange membrane (PEM) fuel cells. In this study, a three-dimensional, non-isothermal, two-phase numerical model is developed to investigate the transport–hydraulic trade-offs introduced by hemispherical baffles embedded in serpentine cathode channels. By systematically varying the baffle radius, the coupled responses of polarization behavior, net power density, pressure loss, oxygen transport, and water management are examined. The results show that the influence of geometric disturbance becomes increasingly pronounced at medium-to-high current densities, where the competition between transport enhancement and hydraulic dissipation governs the overall cell response. An intermediate baffle scale promotes reactant redistribution and facilitates liquid water evacuation, while avoiding excessive flow resistance. Spatial analyses further demonstrate that appropriate hemispherical disturbance improves current density uniformity and mitigates downstream transport limitations. The combined evidence indicates that hemispherical baffles regulate local velocity pathways, pressure dissipation, and species renewal in a strongly coupled manner. This work provides mechanistic insight into geometry-induced transport–hydraulic trade-offs and clarifies the role of baffle scale within the investigated PEMFC configuration.