Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. Additionally, despite the higher electrochemical performance observed, the cell with a counter-flow arrangement featured by a larger hot area and higher maximum temperature gradients is not preferable for a ceramic SOFC system considering thermal durability. Overall, this study could provide insightful thermal information for the operating condition selection, structure design, and stability assessment of realistic SOFCs combined with their internal reforming process.