Evaluation of gas permeability in porous separators for polymer electrolyte fuel cells: CFD simulation based on micro X-ray computed tomography images

TL;DR

This study combines experimental measurements and CFD simulations based on micro X-ray CT images to evaluate gas permeability and pore structures in porous separators for polymer electrolyte fuel cells, revealing anisotropic permeability characteristics.

Contribution

It introduces a CFD simulation approach using micro X-ray CT images to accurately evaluate anisotropic gas permeabilities in porous fuel cell separators, validated by experimental data.

Findings

Simulated porosities and permeabilities agree with experiments.

In-plane permeability is twice the through-plane in conventional samples.

CFD based on micro X-ray CT images effectively assesses anisotropic gas transport.

Abstract

Pore structures and gas transport properties in porous separators for polymer electrolyte fuel cells are evaluated both experimentally and through simulations. In the experiments, the gas permeabilities of two porous samples, a conventional sample and one with low electrical resistivity, are measured by a capillary flow porometer, and the pore size distributions are evaluated with mercury porosimetry. Local pore structures are directly observed with micro X-ray computed tomography (CT). In the simulations, the effective diffusion coefficients of oxygen and the air permeability in porous samples are calculated using random walk Monte Carlo simulations and computational fluid dynamics (CFD) simulations, respectively, based on the X-ray CT images. The calculated porosities and air permeabilities of the porous samples are in good agreement with the experimental values. The simulation results also show that the in-plane permeability is twice the through-plane permeability in the conventional sample, whereas it is slightly higher in the low-resistivity sample. The results of this study show that CFD simulation based on micro X-ray CT images makes it possible to evaluate anisotropic gas permeabilities in anisotropic porous media.