Tuesday, 3 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
PEM Fuel Cells (PEMFC) are attractive because of advantages such as low-temperature operation, no emission of harmful gases and high efficiency. However, the bipolar plates used in the state of the art planar architecture is costly and increases the dead weight of the cell. In addition, the flow channels in the planar fuel cell lead to difficulty in removing the water produced in the cathode during operation of the cell. Cylindrical PEM fuel cells, on the other hand, do not require bipolar plates and also there is no need for precisely machined flow channels. Thus, cylindrical PEM fuel cells are cheap, efficient in water management, and possess higher volumetric and gravimetric power density compared to planar PEM fuel cells. Because of the absence of flow channels in the cylindrical PEMFC, utilization of hydrogen should be enhanced by other means. Effective hydrogen utilization can be realized by controlling operating conditions and also through incorporation of baffles inside the tube. The operating conditions which affect hydrogen utilization are hydrogen flow rate and the cell pressure. Higher flow rates lead to higher velocities, which in turn prevent hydrogen from reaching the anode diffusion layer. Very low flow rates may increase the voltage loss due to concentration polarization. In the case of pressurized cells, high pressure can increase the possibility of a hydrogen leak. The initial results suggest that both the hydrogen flow rate and the cell pressure should be optimized for extracting the best performance from the cylindrical cell. CFD simulations performed on the tubes suggest that the amount of hydrogen reaching the anode differs for different baffle shapes. Therefore, the shape and position of baffles are crucial for improving cylindrical fuel cell performance. The aim of the present work is to analyze the interaction between these operating conditions and design parameters and to propose strategies for better utilization of hydrogen in cylindrical PEM fuel cells.
Keywords: Cylindrical PEM fuel cells, Hydrogen flow rate, Cell pressure, Baffle shape and Baffle spacing