Analysis on temperature uniformity in methane-rich internal reforming solid oxide fuel cells (SOFCs)

Temperature uniformity is a critical parameter in solid oxide fuel cells (SOFCs) since it directly impacts thermal stress, material degradation and output performance. Effective thermal management typically aims to achieve a minimal temperature gradient, especially within a SOFC stack assembled by numerous single cells. In this study, numerical simulations of various boundary conditions and cell designs are performed to investigate thermal uniformity in methane-rich internal reforming SOFCs, which can be utilized as a guidance for design and operation in practical application. The results indicate that the fuel gas with a 5 % mole fraction of methane is more effective in enhancing thermal uniformity through reforming cooling effect at the electrolyte compared to only a 1 % mole fraction. It is strongly recommended in cell design to maintain the ratio of the cell's length to its width (Rcell) greater than or equal to 1.0 considering its better thermal uniformity. However, both increasing the ratio of channel width to rib width (Rc-r) and decreasing the ratio of channel height to channel width (RH-W) have been demonstrated to deteriorate temperature uniformity. Within this study, increasing the backpressure to 1.5 bar is found to result in a 16.7 % reduction in the maximum temperature difference across the electrolyte when compared to that at atmospheric pressure. It is also advisable to operate at the inlet temperature ranging from 973 K to 1023 K for a more uniform temperature distribution within the SOFC.