Cooling Methods for High Temperature Polymer Electrolyte Fuel Cell Stacks

One promising future application for a high temperature polymer electrolyte fuel cell (HT-PEFC) stack coupled with a reformer is an auxiliary power unit (APU) for mobile applications using diesel or kerosene which is also used for the main engine. Despite of the high efficiency of a HT-PEFC, the stack has to be cooled during operation. Hence, this work focuses on the investigation of different cooling strategies regarding the complete system, the use of heat transfer oil as cooling medium is fixed in this contribution. In detail, three cooling methods to maintain operating temperature in stacks with more than 1 kW electrical power and large active areas (> 200 cm2 per cell) were analyzed. In the first method heat transfer oil flows through the stack in internal channels that are located on the backside of the cathode-side bipolar plate. In the second cooling arrangement the oil flows through capsuled cooling cells, which are arranged between every third electrochemical cell. For the third cooling method the excellent heat conducting properties of heat pipes are used. Outside the stack, the heat is removed by heat transfer oil from the overlapping heat pipes. These three methods were evaluated experimentally and with CFD simulations. In this paper the detailed measurements of the temperature distributions are presented containing the overall result that all cooling methods are applicable to maintain the temperatures of large HT-PEFC stacks during the operation in an APU system.