Three-dimensional multiphysics model of a planar solid oxide fuel cell using computational fluid dynamics approach

A multiphysics model of a planar solid oxide fuel cell has been developed based on computational fluid dynamics approach and validated by cell level experiment in the present article. The three-dimensional model of multiphysics nature includes the full-field computational fluid dynamics solutions coupled with the electrochemical model for a planar type of solid oxide fuel cell developed in the Technical University of Denmark. The software COMSOL Multiphysics was used to solve the equations in three-dimensions. With the employment of appropriate boundary conditions at respective parts and through solving the fluid dynamics, heat transfer and electrochemical equations, pressure, velocity, temperature and current density fields were established for a given cell voltage. It is shown that the spatial variation of mole fractions of species are determined by the rate of electrochemical reactions, while that of hydrogen reaching maximum at locations beneath the interconnect ribs and that of oxygen reducing to the fractional level of 2.3 x 10^-4 within the active cathode layer due to the mass flow resistance. The variation of temperature increases as the flow proceeds along the main flow direction due to the electrochemical reactions as well as the ohmic and activation overpotentials. It was shown that the exchange current density field for the anode is determined by the temperature distribution caused by the highly exothermic process of formation of water, and also by the partial pressures of hydrogen and water. It was further established that the variation of overpotential at the anode/electrolyte interface are justified by the mechanisms of irreversible ohmic and activation losses taking place within the cell, a high electronic conductivity in certain locations and the relatively higher ohmic overpotential in respective regions.