Effect of radial flows in fuel channels on thermal performance of counterflow tubular solid oxide fuel cells

Increasing the volumetric power density of solid oxide fuel cell (SOFC) stacks could enable their wider adoption in powering vehicles. The radial flows generated by inserts in gas channels of the tubular SOFC could enhance electrochemical reactions in porous electrodes and improve the power density. In this study, numerical simulations are performed to examine the influence of the enhanced exothermic electrochemical reactions on the temperature distributions in a counterflow tubular SOFC with inserts. We show that the radial flow in the fuel channel could improve the SOFC power density by 30% but lead to an increase in the maximum cell temperature gradient from 12 ℃/cm to 23 ℃/cm. The effects of radial flows under different inlet mass flow rates of hydrogen and methane are also examined. Compared with the conventional tubular SOFC, the percentage of power density improvements and the maximum cell temperature gradients of the tubular SOFC with inserts both increase with increasing inlet hydrogen mass flow rates. The maximum cell temperature gradient is increased from 12.8 ℃/cm to 47.5 ℃/cm as the percentage of net power density improvement is increased from 20% to 45%. We also demonstrate that increasing the inlet methane flow rate could adversely affect the SOFC performance, since the strong radial flow can remove the steam in porous anode, which impedes the methane steam reforming reaction and consequently reduces the output power density. The present work helps improve our understanding of heat and mass transfer characteristics of the radial flows in the tubular SOFC and helps build a foundation for SOFC channel designs.