Simulation of a tubular solid oxide fuel cell through finite volume analysis: Effects of the radiative heat transfer and exergy analysis

This paper presents a very detailed finite volume axial-symmetric model of a tubular internal reforming solid oxide fuel cells (SOFCs), in which the effects of heat/mass transfer and chemical/electrochemical reactions are included. The model allows one to predict the performance of a single SOFC tube once a series of design and operative parameters are fixed, but also to investigate the source and localization of inefficiency. To this scope, an exergy analysis was implemented.The SOFC tube is discretized along its longitudinal axis. Detailed models of the kinetics of the shift and reforming reactions, pressure drops, convection heat transfer and overvoltages are introduced, also based on the work previously developed by the authors. The heat transfer model includes the contribution of thermal radiation, so improving the models previously used by the authors. Radiative heat transfer is calculated on the basis of the slice-to-slice configuration factors and corresponding radiosities. Results showed that radiation is very significant for these types of fuel cells. In fact, the radiative heat transfer dramatically contributes (about 70%) to the radial transfer between the SOFC tube and its air injection tube. The results of the simulation model are also employed in order to verify the correctness of some simplifying assumption diffusely adopted in literature. Based on this simulation model, a case study is presented and discussed. For a fixed set of design and operation parameters, the values of temperature, pressure, chemical composition, electrical parameters and exergy destruction rates are evaluated for each slice of the SOFC tube under investigation. A sensitivity analysis is also performed, in order to investigate the influence of the design parameters on the energetic and exergetic performance of the system.