With these objectives in mind, a tubular PEMFC is developed. Typical PEM fuel cells are planar. Although the tubular geometry has been successfully used in other type of fuel cells such as solid oxide fuel cell (SOFC), it is not common in the case of PEMFC. The tubular cell is observed to have a higher current density than a planar cell using the same commercial 5 layer MEA and under the same operating conditions. A significant reduction in the hardware cost is achieved. The power/weight ratio is found to be several times higher than the commercial planar PEMFCs. Possible reasons for such improvements are investigated through EIS studies. Analysis of this study along with a study on the life expectancy of this cell will be presented. The problems, identified in the process of evaluation, and their possible remedial measures will also be discussed.
In order to optimize the cell dimensions, a steady state model of the cell is developed. In this isothermal half cell model, mass and momentum conservation equations are considered inside the cathode gas flow channel. Mass/species conservation equations are written for the gas diffusion layer and the reaction layer. The reaction layer is characterized as both macro homogenous and spherical agglomerate models. Effects of these characterizations on the model predictions will be presented. In order to reduce the time for computations, the method of Thiele Modulus and effectiveness factor are adopted for the spherical agglomerate characterization. In this model, liquid water is considered in all the layers of the cell. The evaporation/condensation process for water is also considered. Interfacial liquid water saturation can be strongly influenced by the surface properties and the operating conditions of the cell. In order to assess the effects of different surfaces, a sensitivity study is done based on the boundary conditions of the liquid water saturation. The model is validated by the experimental data collected over a wide range of air flow rate and operating pressure.