Effects of roughness of gas diffusion layer surface on liquid water transport in micro gas channels of a proton exchange membrane fuel cell

Effects of surface roughness of a gas diffusion layer (GDL) on liquid water transport in a micro gas channel (GC) of a proton exchange membrane fuel cell (PEMFC) are investigated by using the volume of fluid (VOF) method in the commercial CFD package, FLUENT 6.3.26. An array of cubic holes under the GDL surface is used to describe the GDL surface roughness. The simulation results show that a Cassie droplet is inclined to form on the hydrophobic rough GDL surface and the surface roughness greatly affects the transport of the droplet. Effects of GDL surface roughness on forces acting on the droplet are carefully studied, and it is found that GDL surface roughness reduces the retentive forces and increases the detaching forces. In addition, effects of GDL surface roughness on the time required for a droplet to be removed out of the GC, liquid water coverage area ratio on GDL surface, and pressure drop in the GC are explored. The removal time of the water droplet decreases as the GDL roughness increases. The water coverage ratio of the GDL surface decreases as GDL surface roughness increases. The pressure drop in the GC increases as the GDL surface roughness increases.