Analyzing the thermal and electrical performance of a tubular SOFC with inserts by mass transfer coefficients

Low power density and large temperature gradient are the key factors restricting the wider adoption of solid oxide fuel cell stacks in powering vehicles. Placing inserts in the flow channels to control electrochemical reaction and heat generation could improve power density or reduce temperature gradient. In this study, we constructed a 2-D axisymmetric model to investigate the influence of the geometric parameters and operating conditions of a tubular SOFC with inserts on its electrical and thermal performance. The average mass transfer coefficient is proposed for quantitative analysis. An increase in average mass transfer coefficients indicates stronger diffusive mass transfer in porous electrode and convective mass transfer in flow channels, which could in general lead to higher cell output powers and larger local temperature gradients. We show that the cell performance is more sensitive to the parameters of the anode side than that of the cathode side due to the existence of the inserts in fuel channel. The cathode thickness and porosity barely affect the average mass transfer coefficient. We demonstrate that fuel inlet velocity is the primary factor affecting the cell output power while the anode thickness significantly affects the maximum cell temperature gradient. As the fuel inlet velocity varies from 1.0 m & sdot;s  1 to 4.0 m & sdot;s  1, the output power could be increased by 50 %, and the maximum cell temperature gradient could be doubled as the anode thickness decreases from 1 mm to 0.25 mm. The influence of the cell geometric parameters on the cell output power is smaller than that of the fuel inlet flow rate. This study demonstrates the effectiveness of quantitative analysis based on average mass transfer coefficients. It helps improve our understanding of the heat and mass transfer performance in solid oxide fuel cells.