A numerical model coupling the heat and gas species' transport processes in a tubular SOFC

A numerical model is presented in this work that computes the interdependent fields of flow, temperature, and mass fractions, in a single tubular solid oxide fuel cell (SOFC). Fuel gas from a pre-reformer is considered to contain H₂, CO, CO₂, H₂O (vapor), and CH₄, so reforming and shift reactions in the cell are incorporated. The model uses mixture gas properties of the fuel and oxidant that are functions of the numerically obtained local temperature, pressure, and species concentrations, which are both interdependent and related to the chemical and electrochemical reactions. A discretized network circuit of a tubular SOFC was adopted to account for the Ohmic losses and Joule heating from the current passing around the circumference of the cell to the interconnect. In the iterative computation, local electrochemical parameters were simultaneously calculated based on the local parameters of pressure, temperature, and concentration of the species. Upon convergence of the computation, both local details and the overall performance of the fuel cell are obtained. These numerical results are important in order to better understand the operation of SOFCs.