Microscopic investigation of multi-transfer characteristics in digitally replicated porous gas transport media with locally variable through-plane porosities of Eulerian formulae for electrochemical applications

Abstract

In this study, the microscopic transport characteristics of carbon fiber-based porous gas transport media (PGTMs) with locally variable through-plane porosities are statistically investigated. Gradient porosity distributions from 0.95 to 0.55 are mathematically described in either Eulerian (convex/concave) or linear forms along the PGTM thickness. The PGTMs are randomly generated based on the pre-calculated volume fractions of each component. Various transport characteristics (i.e., momentum, mass, heat, and charge transfer properties) are numerically estimated in PGTM samples with gradient porosities and compared to those of PGTMs with uniform porosity. The mass transport phenomena throughout the PGTMs are simulated using a D3Q19 (i.e., three-dimensional, 19-velocity) lattice Boltzmann method (LBM). The corresponding results reveal that PGTMs with a concave porosity distribution possess higher permeability and are more favorable for mass transfer than those with uniform porosity owing to larger local pore diameters. In addition, PGTMs with a convex porosity distribution exhibit the highest electrical and thermal conductances compared to other PGTM samples owing to the highest fiber volume fractions. Finally, the effects of the porosity distribution on various transport resistances in PGTMs are quantitatively evaluated and compared.