Electrochemical and Thermo-Fluid Modeling of a Tubular Solid Oxide Fuel Cell with Accompanying Indirect Internal Fuel Reforming

Development of fuel cells has been boosted by global and regional environmental issues. Among others, the solid oxide fuel cell (SOFC) has been drawing much attention as a unit for distributed energy generation. Numerical analysis is used as a powerful tool in research and development of field cells, especially of the SOFC for which important and necessary thermal management information has scarcely been supplied experimentally. A central issue for achieving maximum benefit from the numerical analysis is how to properly model the complex phenomena occurring in the fuel cells. This chapter presents a numerical model for a tubular SOFC including a case with indirect internal reforming. In this model, the velocity field in the air and fuel passages and heat and mass transfer in and around a tubular cell are calculated with a two-dimensional cylindrical coordinate system adopting the axisymmetric assumption. Internal reforming and electrochemical reactions are both taken into account in this model. Electric potential field and electric current in the cell are also calculated simultaneously allowing their nonuniformity in the peripheral direction. A previously developed quasi-two-dimensional model was adopted to combine the assumed axisymmetry of velocity, heat and mass transfer fields and the peripheral nonuniformity of electric potential field and electric current. Details of those numerical procedures are described and examples of the calculated results are discussed. After presenting a re fundamental results, several strategies to reduce the maximum temperature gradient of the cell are examined for a case with indirect internal fuel reforming.

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