A comprehensive numerical model for tubular SOFC with internal reforming is developed. Navier-Stokes equations, energy equation and mass transfer equations for chemical species are solved in conjunction with electrical circuit and electrochemical reactions. Heat produced by ohmic resistance and chemical reactions is considered in the simulation. Three main kinds of irreversibilities exist in SOFC due to the presence of porous electrodes and electrolyte. Those are concentration overpotential, ohmic overpotential and activation overpotential. Therefore, appropriate overpotential model is a fatal factor for the successful modeling of electrical performance, heat and mass transfer of SOFC. In this paper three different activation overpotential models have been compared for tubular SOFC simulation. The results of current density, output power and the thermal fluid field distribution within a tubular SOFC unit are discussed in detail.
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