| Summary: | Thermal management is an essential aspect in the design and operation of a Polymer Electrolyte Membrane (PEM) fuel cell where cooling effectiveness directly influences energy conversion performance. Two air-cooled closed cathode PEM fuel cell stacks with varied cooling channel aspect ratio was developed for experimental cooling effectiveness analysis. The first stack, labeled D1, integrates 40 cooling channels with an aspect ratio of 1.7 while stack D2 has 20 channels with an aspect ratio of 3.8. The analysis is focused at 20A and 30A loads and applied a cooling fan coupling of positive and negative pressure flows. The cooling air humidity was varied by humidifying the air from an ambient value of 50% to 90% relative humidity. The translation of mean stack temperature data to stack energy changes shows an exponential cooling response profile. A steady-state cooling rate were obtained from the stack cooling profile and compared with the generated thermal energy to obtain the cooling effectiveness at each operating mode. Stack D1, with lower aspect ratio and higher number of channels, yields a better cooling performance with dry air with the penalty of slower cooling response. Larger channels of stack D2 show a greater compatibility to moist air cooling with cooling stability as another strong characteristic.
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