Measurements of Anisotropy of the Effective Diffusivity through PEFC GDL and Mass Transfer Resistance at GDL and Channel Interface

Abstract

Gas transport through the gas diffusion layer (GDL) is important in Polymer Electrolyte Fuel Cell (PEFC). GDL consists of random fiber structure, so GDL may have anisotropy for the transport properties. We have developed the measuring method of the effective diffusivity through GDLs and measured those through-plane and in-plane values. In this work, the effective diffusivity through GDL on each directions and the convection mass transfer at GDL-Channel interface were investigated. The coefficient has been measured in various gas flow rate and diffusion area of GDL of especially through-plane direction. It was found that the in-plane diffusivity is higher than the through-plane value. In addition, convective mass transfer was evaluated by using Sherwood number and compared with asymptotic results for laminar convective mass transfer. The resulting Sherwood number closed to asymptotic results almost.