Radiative and convective heat transport within tubular solid-oxide fuel-cell stacks

This paper develops a relatively simple model that is intended to rapidly evaluate design configuration and operating conditions for tubular anode-supported solid-oxide fuel-cell (SOFC) stacks. Heat is removed from the SOFC tubes by a combination of convection and radiation. Heat is convected to air that circulates outside the SOFC tubes and radiated to a surrounding cylindrical wall. The tubes are assumed to be arranged in hexagonal arrays in which the distance between tubes centers form equilateral triangles. The paper presents new configuration-factor formulas that are needed to represent arrays of staggered cylinders. The configuration factors are derived for long cylinders using the crossed-string method. These configuration factors have general utility beyond the application to fuel-cell systems. The model is applied to a particular cell and stack system and used to evaluate the effects of a range of design and operating conditions.