Multimodal Mass Transfer in Solid-Oxide Fuel-Cells

A new model and algorithm for the numerical simulation of multicomponent mass-transfer in solid-oxide fuel-cells (SOFCs) is presented. The model does not neglect any of the possible molecular mass-transfer mechanisms present in a SOFC. It takes into account convection and molecular-diffusion phenomena in the channels, and convection, molecular diffusion and Knudsen diffusion in the porous electrodes. The model does not require any of the constraining hypotheses present in previously published ones. Its noteworthy features are: (i) pressure is not considered as constant (in any direction) in the channel or in the electrode; (ii) global mass transfer through the porous media is modeled by means of the Dusty Gas Model, without any limiting assumption on the number of species in the multicomponent gas mixture; (iii) the physical phenomena in channel and porous medium are coupled through boundary conditions and solved simultaneously; (iv) the model can be used for both the anode and the cathode. The algorithm is designed to simulate multidimensional domains and is applicable to both planar and tubular cells. It has been implemented using OpenFOAM (open field operation and manipulation), an open-source finite-volume-method based CFD-tool. The model performance has been successfully validated by comparison with experimental data reported in the literature for both main types of SOFC, planar and tubular.