Volume 31: Clean Energy Technologies towards Carbon Neutrality

Pore-scale Investigation of a Gas Diffusion Layer Model Coupled Mass Transfer and Two-phase Flow: Effects of the Compression Ratio Lingyi Guo1, Li Chen, Wen-Quan Tao

Abstract

Reducing water flooding and enhancing oxygen transport in the gas diffusion layer (GDL) of proton exchange membrane fuel cells are of great importance for optimizing cell performance. In this study, a pore-scale model based on the lattice Boltzmann method is proposed, which considers two-phase flow, oxygen diffusion and electrochemical reaction. The pore-scale model is then adopted to explore multiphase reactive transport processes in the GDL. Effects of compression on the liquid water saturation and current density are explored. It is found that, by increasing the compression ratio from 0.2 to 0.4, the current density increases by 4.7%, with obvious relieve of the water flooding under the rib and increment of the number of reaction sites under the gas channel. Besides, the results demonstrate that while reducing the total saturation in the GDL is important, decreasing the local saturation near the interface of the microporous layer/GDL is also crucial for enhancing cell performance. The coupled method can directly reveal the effects of GDL compression on water flooding and oxygen reactive transport, which provides a new insight for optimizing cell performance.

Keywords proton exchange membrane fuel cell, liquid water, gas diffusion layer, oxygen reactive transport, compression ratio