Three-Dimensional Multiphysics-Coupled Simulation of Tubular Solid Oxide Fuel Cells: Scaling Effects and Thermal Management

Solid oxide fuel cells (SOFCs), as high-efficiency clean energy technologies, require performance and thermal management optimization to enhance reliability. This study develops a three-dimensional model to examine the combined effects of cathode length, reactant distribution, and flow channel parameters in tubular SOFCs. The results indicate that increasing the cathode length boosts output power by 280% but reduces power density by 45.8%, highlighting the trade-off between active area expansion and concentration polarization. The gradual depletion of hydrogen and oxygen along the flow path exacerbates current density heterogeneity. Temperature field analysis shows a maximum temperature of $662.77^{\circ} \mathrm{C}$ in the anode active zone. Counter-flow cooling alleviates localized overheating, while significant thermal gradients persist in the middle and later sections. Optimization strategies show that increasing the air channel height to 2.0 mm reduces the temperature by $10.69^{\circ} \mathrm{C}$, while increasing the air flow rate to $350 \mathrm{ml} / \mathrm{min}$ lowers the peak temperature by $20.24^{\circ} \mathrm{C}$. This work offers a theoretical foundation for the multi-parameter collaborative design of SOFCs and supports their application in renewable energy power systems.