Transient simulation of a tubular micro-solid oxide fuel cell

A 2D-axisymmetric model is developed for a tubular micro-solid oxide fuel cell (T mu SOFC), detailing heat, mass, momentum, and charge transfer as well as electrochemical reactions. Thermal transients are simulated. No parameter fitting was done, and only kinetics parameters estimated in our previous work for isothermal, steady state conditions are used. Transient experiments were conducted for this study and the data are presented. The purely predictive simulation results are found to be consistent with experimental results. The model is used to simulate the transient behavior of a step in cell current and air flow. The sensitivity of transients to several parameters are simulated and discussed. It is found that in general, transients of the system were controlled by the thermal transients indicating that other transients were much faster. Therefore, a fast electric response results from a small thermal mass of the system. Two modes could be identified in the thermal transients: fast and slow; the former is found to be associated with the cell itself, while the latter was found to be due to the furnace wall surrounding the cell. A step in current resulted in a sharp drop in voltage and its gradual recovery, which is a result of the cell slowly heating up.