Numerical investigations of liquid water mobility with various flow regimes in proton exchange membrane fuel cells

The removal of liquid water from proton exchange membrane fuel cell (PEMFC) channels is investigated using the volume of fluid (VOF) method, considering contact angle hysteresis. The process is influenced by the adhesion force induced by contact angle hysteresis and the drag force, which varies with droplet morphologies and flow regimes. Various flow regimes, including droplet, film, slug, and corner flows, are analyzed in terms of detachment velocities, volumes, pressure drops, and wetted-area ratios on gas diffusion layers (GDLs). Results show that film flow is harder to remove than droplet flow and wets a larger area on the GDL, restricting gas diffusion to the catalyst layers. In contrast, corner flow is more difficult to move than slug flow, but it does not impede gas diffusion due to minimal GDL wetting, leading to less performance loss. Moreover, semicircular turns improve water removal and reduce channel pressure drop compared to right-angle turns, enhancing fuel cell efficiency.