Maxwell-Stefan Diffusion in a Fuel Cell Unit Cell
Model ID: 247
In concentrated gases and liquids, where the concentrations of species are of the same order of magnitude, there is no obvious solvent-solute relationship. Fick’s law for diffusion accounts only for one-way solute-solvent interactions whereas the Maxwell-Stefan equations account for all interactions of species in a solution. In a system with three components, three pair-wise interactions are present, while for a system of four components there are six such interactions. These interactions are described as Fick-analogous Maxwell-Stefan diffusion coefficients.
This example models the steady-state mass transport in the cross section of a proton exchange membrane fuel cell cathode. It models the mass transport in the 3-component gas mixture by using a Concentrated Species interface including a Maxwell-Stefan diffusion model. The cross section includes the channel and current collector in the bipolar plate, at the upper boundary, while the active layer defines the lower boundary.
The purpose of this model is to show how to consider Maxwell-Stefan diffusion in mass transport.
|A surface plot showing the mass fraction of oxygen at 0.8 V overvoltage of the cathode (an almost short circuit of the fuel cell).|