Modeling the temperature field in the reforming anode of a button-shaped solid oxide fuel cell

摘要

A model predicting the temperature field in the porous reforming anode of a solid oxide fuel cell is presented herein. The model is based on mass, momentum, and heat balances of a chemically reacting mixture of gases within the porous matrix of the anode. The important novel characteristic of the model is the consideration of the both internal reforming and electrochemical reactions in the bulk of the porous anode. The electronic and ionic currents in the anodes are calculated utilizing the solution of the Poisson equations for the electric potentials in the porous medium. The transfer current density is described by the Butler-Volmer equation. The model is applied to investigate the temperature field and the reactive flow in button-shaped fuel cells with uniform and graded (multi-layer) anodes composed of Ni and YSZ particles with methane/water vapor mixture used as the fuel. The maximum temperature difference between the hot and cold spots of the anodes is found to reach up to 200 K. The results indicate that the generation of Joule heating caused by the current passing through the anode and the activation losses are the dominating heat sources compared to the gas-water shift and electrochemical reactions.