Diffusion parameter correlations for PEFC gas diffusion layers considering the presence of a water-droplet

A polymer electrolyte fuel cell (PEFC) produces electrical energy according to the electrochemical reactions carried out inside the cell. During the energy conversion, water molecules are also produced at the cathode side, which affects the gas diffusion layer (GDL) diffusion parameters. The generated water-drops from the reaction may give partial or total blockage of the reactant gases and also material oxidation. The mentioned phenomena influence the performance of the PEFCs. This paper aims to describe and quantify the impact on diffusion parameters of GDLs when the size of the formed water-drops inside the layer is varying. This study considers digitally generated GDLs, in which the porosity, gas-phase tortuosity and diffusibility are studied. The fluid flow behavior through the three-dimensional porous domain representing the GDL is obtained with the lattice Boltzmann method (LBM). Depending on the water-drop size, the impact of the mentioned parameters can be computed. For the current study a spherical water-drop whose radius varies between the 15 and 35% of the size of the domain was considered. The studied parameters showed a dependency of the water-drop radius, each changing independently and several correlations to predict the behavior of the mentioned diffusion transport parameters are proposed. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.