CFD-Based Design of Microtubular Solid Oxide Fuel Cells

Microtubular solid oxide fuel cells (MT-SOFCs) are interesting for portable and auxiliary power units energy production systems, due to their extremely fast startup time. However, a single cell provides power in the range of 1 W, thus the number of microtubes to reach a kW scale is relevant and packaging design issues arise also. In this paper a specifically developed design procedure is presented to face with system issues and bringing into account fluid-dynamic and thermal influence on system performance. The procedure also simplifies the stack manifold design by means of a modular scale-up procedure starting from a basic optimized configuration. To this aim, a computational fluid dynamics (CFD) model has been integrated with specific models for fuel cell simulation and then validated with tailored experimental data by varying operating conditions in terms of fuel utilization and electric load. A comprehensive three-dimensional (3D) thermal-fluid-dynamic model has then been applied to the analysis of both micro-assembly (i.e., 15 tube assembly) and midi-assembly (up to 45 tubes), showing an important role of local phenomena as current homogeneity and reactant local concentration that have a strong influence on power density and temperature distribution. Microreactor power density in the range of 0.3 kW/l have been demonstrated and a specific manifold design has been realized paving the way toward a modular realization of a 1 kW MT-SOFC.