Numerical simulation of liquid water behavior in microchannel with a 90° bend

Water management is an effective way of improving Proton Exchange Membrane (PEM) fuel cell performance and durability. Changing the wettability of gas channel walls and gas diffusion layer (GDL) is one way of controlling the water management in a fuel cell for its influence on the liquid water dynamic behavior. The objective of this study is to investigate liquid water dynamic behavior in a microchannel with a 90° bend and different surface wettability combinations through 3-D numerical simulation. Volume-of-fluid (VOF) method was employed to track the fluid-fluid interface in the multiphase flow. The simulated microchannel has a square cross-section with a dimension of 0.25 mm and a total length of 1.5 mm. Water is introduced to the channel via two pores in the bottom surface representing a GDL while air flows from one end to another. The air and water velocities used are in the order of magnitude of a high current density fuel cell. Nine different combinations of wall/GDL wettability are investigated. The results show that liquid water takes less time to leave the channel in a hydrophilic GDL compared to moderate and hydrophobic GDL regardless of wall wettability. Furthermore, the GDL wettability shows more significant impact on liquid water behavior compared to the wall wettability; however, wall wettability has a slight but considerable impact.