Two-Dimensional Simulations of Gas-Liquid Two-Phase Flow in Mini channels of PEM Fuel Cell Flow Field

Abstract

Effective water management is one of the key strategies for improving the performance and durability of PEM fuel cells. Phenomena such as membrane dehydration, catalyst layer flooding and two-phase flow in flow-channels are all determined by the distribution and movement of water during cell operation. In this study, gas-liquid flow in mini-channels relevant to fuel cells was numerically studied using a CFD two-phase flow model in combination with a volume of fluid (VOF) method. The results show that the surface wettability of the channel wall can greatly affect the flow pattern, especially when the channel walls and the gas diffusion layer (GDL) surface possess different contact angles. When the channel walls are more hydrophobic, more water is accumulated on the GDL. An increase in the surface tension results in a slight increase of slug frequency and a slight decrease in slug length. The onset of slugging along the channel is determined by the gas-liquid mixture velocity, gas-to-liquid flow ratio and the way water is introduced into the gas flow channel. Furthermore, the calculated pressure drop fluctuations show a strong dependence on the channel liquid content and the slug length.