Local heat transfer enhancement by recirculation flows for temperature gradient reduction in a tubular SOFC

The large temperature gradient in solid oxide fuel cells (SOFCs) severely degrades their operation reliability. In this study, we have developed a numerical model to examine the effect of local heat transfer enhancement on the temperature gradient reduction in a counter-flow type micro-tubular SOFC. The local heat transfer is enhanced by placing turbulators in the SOFC air channel. We show that turbulators in air channels could induce recirculation flow, which increases the local convective heat transfer coefficient and facilitates the heat dissipation from electrodes to air stream. A spatial temperature gradient diagram is proposed to analyze the influences of turbulator radii, locations and pitches on the cell axial temperature gradient reduction. The turbulator effectively decreases the largest temperature gradient and reduces the region where the temperature gradient is higher than 30℃/cm. We also compare the temperature profile and air-side pressure drop between tubular SOFCs with turbulators and thin air channels. The SOFC with turbulators is demonstrated to achieve comparable heat transfer performance but at a lower air-side pressure drop than that with a thin air channel. Our work demonstrates the effectiveness of local heat transfer enhancement on SOFC temperature gradient reduction and proposes a new diagram to quantitatively evaluate the impact of the thermal management methods through local heat transfer enhancement.