Investigation of the Dynamic Behavior of Water Transport at the Bend of a Serpentine Cathode Channel of a Polymer Electrolyte Fuel Cell

The present study focuses on the investigation of the dynamic behaviour of water at the bend of a cathode channel. A two-phase volume of fluid (VOF) model has been utilized to track the interface of water droplet as it emerges from a gas diffusion layer of a polymer electrolyte fuel cell into the cathode channel and then accumulates at the bend. The water droplet dynamic has been investigated for hydrophobic and hydrophilic channel walls, whereas the wettability of the gas diffusion layer surface is kept hydrophobic. A microchannel bend with a square cross section of 0.25 mm has been adopted for the study. The emergence of a single water droplet from a 0.05 mm pore and its deflection and detachment from the pore and attachment at the bend wall has been investigated. The simulation results show that the wettability of the channel walls has significant effects on the water transport. The hydrophilic side wall at the bend results in significant water accumulation as film at the bend corners, edges and top wall. The water removal rate is low and the incoming droplets merge with the existing water film. The hydrophilic side wall, however, results in minimal water coverage on the bottom wall as the water film resides on the side and top walls. On the other hand, the hydrophobic wall results in faster water removal and minimal water saturation in the channel. The hydrophobic wall, however, results in slightly increased water coverage on the bottom wall as the water droplet detaches from the side walls after the bend and flows along the bottom wall. The paper also presents results obtained from the investigation of the effects of the orientation of the cathode channel - that is the effects of horizontal or vertical stacking of the cell and shows that effects of orientation on water movement is negligible.