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3D-modeling of an integrated SOFC stack unit

: Ganzer, G.; Schöne, J.; Beckert, W.; Megel, S.; Michaelis, A.

European Fuel Cell Forum -EFCF-:
10th European Solid Oxide Fuel Cell Forum, SOFC 2012. Proceedings : Fundamentals, Materials, Systems, Applications; 26 - 29 June 2012, Lucerne/Switzerland
Oberrohrdorf/Switzerland: European Fuel Cell Forum, 2012
European Solid Oxide Fuel Cell Forum (SOFC) <10, 2012, Luzern>
Fraunhofer IKTS ()

Solid oxide fuel cells (SOFCs) are promising candidates for future energy supply by converting the chemical energy of the reactants directly into electrical energy. In this work, a thermo-fluid and electrochemical SOFC stack model of an existing stack is introduced. The stack is made of 30 repeating units in cross-flow design with an internal manifold system. In SOFC stacks different transport processes are present: heat and mass transfer, fluid flow and electrochemical conversions. Furthermore, different length scales can be found, ranging from several microns for the electrolyte thickness to some decimetres referring to stack height. Therefore, a detailed simulation is computationally expensive. To reduce computational costs, a homogenized description of the electrochemical active area, treated as a porous medium, is introduced. Additionally, the model comprises internal anode and cathode manifolds. Firstly, a comparison between a detailed and two homogenized thermo-fluid models of one repeating unit will be performed in order to verify our homogenization approach. The homogenized models show good agreement with the detailed case. In the second part, a homogenized thermo-fluid stack model is integrated into a hotbox environment, leading to a more realistic stack surrounding. In this case, the stack has an open cathode; the air supply through the hotbox induces a more uneven flow distribution at the cathode entrance. The influence of two different heat source distributions inside the stack will be compared. Finally, a two-dimensional electrochemical model of the active are a will be introduced. Temperature distributions for two fuel gas compositions, pure hydrogen and methane, are shown.