Experimental investigation of liquid water droplet removal in a simulated polymer electrolyte membrane fuel cell gas channel with gas diffusion layer characteristics

Abstract

Since the accumulation of liquid water droplets in gas flow channels significantly affects the performance of polymer electrolyte membrane (PEM) fuel cells, a comprehensive understanding of liquid water removal from the cell is of great importance to achieve optimal water management. This study is mainly concerned with the ex situ measurement of water droplet growth and its removal in a non-reacting simulated cathode channel for PEM fuel cells. To this end, the dynamic behavior of a liquid water droplet at the gas flow channel/gas diffusion layer (GDL) interface was investigated experimentally using a specially designed transparent cell device with different GDLs. The effects of the GDL parameters (GDL thickness and micro-porous layer (MPL) inclusion) on water droplet removal are mainly investigated by analyzing the contact angle hysteresis with inlet air flow rate (Reynolds number). The critical Reynolds number is employed to evaluate the droplet removal from the GDL surface. It is observed that the water droplet on a thinner GDL tends to be removed under a higher critical Reynolds number. In addition, it is shown that the GDL with an MPL requires a higher critical Reynolds number for the water droplet removal under the same droplet height. The results suggest that the structure of the GDL sample has considerable influence on the water droplet removal. It is thought that the data obtained from this study can provide useful insight into the design of a GDL with enhanced water removal capability for PEM fuel cells.