3.3 Modeling Fluid Flow, Heat Transfer, and Mass Transfer

All aspects of fluid flow, heat transfer, and mass transfer in the flow channels and porous electrodes are handled by ANSYS FLUENT.

The default multicomponent diffusion model in ANSYS FLUENT is used to calculate the mass diffusion coefficient of species $i$ in the mixture.

To account for the effect of porosity on the multicomponent mass diffusion coefficient

where $\epsilon$ is the porosity and $\tau$ is the tortuosity (i.e., the average path length over the actual length).