(294f) A Two-Phase Two-Dimensional Steady State Model of a Cylindrical PEM Fuel Cell Cathode

Traditional polymer electrolyte membrane fuel cells (PEMFCs) are planar. Cost and water management are two major issues with this design. To improve the gravimetric and volumetric power densities of the PEMFC and to reduce the cost, a novel cylindrical PEMFC design has been developed. The performance of the air-breathing cylindrical PEMFC is found to be superior to a state-of-the-art planar cell in the high current density region. To understand the effect of various design parameters and operating conditions on the performance of the cylindrical PEMFC and to optimize its design, a two-dimensional, two-phase, steady-state model of the air-breathing cylindrical cell is developed.  For comparison, a similar model of the planar cell is also developed. The model of the planar cell is validated with the data from a state-of-the-art commercial cell while the model of the air-breathing cylindrical cell is validated with the experimental data from an in-house cell. For comparison, same membrane electrode assembly (MEA) is used in both the cells. The ohmic resistances used in both the models are determined by electrochemical impedance spectroscopy (EIS).   The developed models are utilized for analyzing the reasons for superior performance of the cylindrical PEMFC. The model of the air-breathing cylindrical PEMFC is extended to a pressurized cell by modeling the gas flow channel. The performance of the pressurized cell is found to be considerably higher than the air-breathing cell. A number of parametric studies are done with the model of the pressurized cell. The temperature is found to have a modest effect on the performance in the temperature range studied. As the air flow rate is increased from a low flow rate, the cell performance improves significantly. Further increase in the flow rate has negligible effect. The study suggests that there is an optimum platinum loading because of an interplay between the change in the activation losses and concentration losses as the platinum loading is changed. The study also shows that an optimum loading of ionomer content can improve the cell performance especially at higher current densities. The parametric studies show that a multivariable optimization study can significantly improve the cell performance in the entire polarization range.