Effect of three-dimensional geometric structure and surface wettability on two-phase flow behavior in a proton exchange membrane fuel cell gas flow channel: modeling and simulation

Abstract

Improving water management capability is crucial for enhancing the performance and extending the lifespan of a proton exchange membrane fuel cell (PEMFC). To achieve this goal, this study investigates the coupling effects of geometric features induced by actual gas flow channel (GFC) manufacturing processes and the surface wettability on the dynamic droplet change by simulating 32 cases using the volume of fluid (VOF) method. In addition, the simulated dynamic characteristics of the droplets, such as the centroid position and droplet height, have been verified by comparing them with experimental observations. The reliable results of the simulation show that varied draft angles contribute to different local vortices in the flow channels, arousing two drainage mechanisms—spontaneous and overflow drainage. Besides, the compared results of velocity contours suggest that the curvature effect along the water movement direction could strengthen the speed-up effect around a water droplet, thereby facilitating its detachment. By contrast, a cross-section with filleted corners could cause velocity loss and poor drainage efficiency. A geometric structure with a draft angle of 30° and a bend radius of 1 mm of wavy GFC is beneficial to shorten the water removal time and minimize gas diffusion layer (GDL) water coverage. The hydrophobic treatment of the GDL and channel wall meets both criteria of rapidly reducing liquid water coverage on both the GDL surface and the entire channel. This study's findings are expected to guide the target of both geometric manufacturing and surface treatment processes.