SHEN Shuanglin ¹, ZHUO Xiaoling ¹, ZHENG Keqing ¹, LING Yihan ², WANG Shaorong ³
(1. School of Low-Carbon Energy and Power Engineering, China University of Mining and Technology, Xuzhou 221116,Jiangsu, China; 2. School of Materials Science and Physics, China University of Mining and Technology, Xuzhou 221116,Jiangsu, China; 3. School of Chemical Engineering and Technology, China University of Mining and Technology,Xuzhou 221116, Jiangsu, China)

Abstract: Numerical modelling of solid oxide fuel cell (SOFC) is always limited by the contradiction between accuracy and computational resource demand, while mesh density in catalyst layer (CL) has significant effect on the accuracy and computational resource demand, but optimization of the two factors has rarely reported. A three-dimensional numerical model for SOFC repeating unit is developed by combing gas flow, heat transfer, species transfer, change transfer and electrochemical reaction equations. The effect of mesh density in CL on performance predicted by this model is studied by using five sets of mesh with different elements in the CL, whereas the mechanism is analyzed. It is found that the performance increases with increasing mesh density in the CL and the increment grows with increasing output current density. The mechanism is studied basing on the Butler-Volmer equation, distribution of electrical and ionic potentials and current generated in the thickness direction of the CL. Also, similar distributions in electrical and ionic potentials in CL are present for different mesh densities, while the generated current increases exponentially nearby the electrolyte layer (EL). The output current is the integral of the generating current in the thickness direction. This is because the numerical integral of generated current is calculated by assuming a linear distribution. According to this mechanism, several improved methods are discussed, thusleading to a simple method to correct the generated current in first layer of CL mesh by using the generating layer at the CL/EL interface. Therefore, the relative error of output current density can be reduced by about 50%.
Key words: fuel cell; numerical simulation; mesh density; model accuracy; catalyst layer