Numerical investigation on the optimized design and wall film behavior of gas-water separators in the proton exchange membrane fuel cell

This study numerically investigates baffle gas-water separators for PEMFC systems to enhance water removal and reduce pressure loss. A coupled discrete phase model and Eulerian wall film model simulate multiphase interactions, focusing on wall film behavior and droplet dynamics. Key design parameters, including baffle count, spacing, and the vertical distance from the inlet to the lowest baffle, are systematically analyzed to reveal how geometric optimization influences flow turbulence and wall film re-entrainment. Results show that reducing the vertical distance suppresses turbulence intensity, stabilizes flow, and limits secondary droplet formation. Droplet rebound primarily generates fine droplets, whereas shear-induced film stripping leads to larger droplets. An optimized three-baffle configuration significantly reduces film accumulation and instability-driven re-entrainment, achieving high separation efficiency with a 46 % reduction in pressure loss compared to a six-baffle design. These findings offer an efficient solution for PEMFC water management. • More baffles do not necessarily improve gas-liquid separation efficiency. • Larger inlet-to-lowest baffle distance enhances separation and stabilizes the flow. • Film stripping forms large droplets and contributes to downstream accumulation. • Rebound produces fine droplets and causes flow re-entrainment. • Three-baffle design keeps efficiency with 46 % lower pressure loss than six baffle.