Numerical study of a 20-cell tubular segmented-in-series solid oxide fuel cell

Tubular segmented-in-series solid oxide fuel cells (SIS–SOFCs) have the advantages of good thermal shock resistance, mechanical strength, and easy sealing because of their tubular structures, and they gain a high operating voltage due to their series configuration. Previous studies have mainly focused on the optimization of a single cell segment while ignoring the flow and heat transfer between series cells. In this study, a 20-cell in-series SOFC model is developed by coupling the electrochemical reactions and mass, momentum, and heat transfer processes. The temperature and composition have a striped distribution because of the noncontinuous electrochemical reaction area. The discontinuity of the heat generation and the intrinsic limit of the access air cooling lead to temperature nonuniformity, while the uneven temperature and component consumption result in the nonuniform voltage of each series cell. For the problems of nonuniform temperature and voltage distributions in the SIS–SOFC, two effective solutions are proposed and evaluated. By introducing a heat pipe as a fuel inlet tube and increasing the length of the downstream cell in turn, the temperature difference is reduced from 111 K to 25 K, and the voltage difference is decreased from 120 mV to 7 mV at an operating current of 3 A.