Abstract
Stack power is one of the most critical criteria in fuel cell applications. Most FCVs have increased maximum stack power up to 100kW to acquire some design margin such as service lifetime, vehicle drivability, and system efficiency. Hyundai / Kia Motors have already unveiled in-house 80kW-class stack in 2005. And new bipolar plate designs for higher power over 80kW were demonstrated in 2007. In this work, the characteristic water removal from a full-sized fuel cell is analyzed with coolant- controlled thermal boundary conditions. High frequency resistance (HFR) along with neutron radiography (NR) is used to elucidate the characteristic variation of water content in the membrane and in other components in the fuel cell during operation and purge, respectively. During operation, the variation in stored water content was also investigated for different relative humidity (RH) and power conditions. The effect of purge was analyzed by shutting the current off and by holding the reactant flow rate constant during polarization, and the change of water content was investigated for the whole fuel cell and the membrane, respectively. Interestingly, it was determined that water removal from the membrane can be, to some extent, separately controlled from the flow field and porous media by utilizing proper purge conditions.
Keywords: Polymer electrolyte fuel cell, Neutron radiography, Bipolar plate, Gas purge