| Summary: | 博士 === 元智大學 === 機械工程學系 === 95 === The present study investigates both experimentally and theoretically the effects on fuel cell performance of non-uniform porosity and permeability in the gas diffusion layer (GDL) due to clamping force. In the experimental study, various kinds of gaskets are used to simulate various compression ratios of the GDL. In the theoretical simulations, a relevant GDL compressed model and a three-dimensional proton exchange membrane (PEM) fuel cell model are developed to simulate multi-physic transport based on code from the Computational Fluid Dynamics Research Corporation (CFDRC). The results of the numerical simulation are compared and showed in good agreement with that of experiments in overall fuel cell performances.
Further detailed investigations are made in comparing the present non-uniformly compressed model with its commonly assumed uniformly compressed model. It is shown that, although both models yield almost the same total performance at working voltage range, their local distribution characteristics are far different such that the uniform compressed model can not predict well the local phenomena. Also, the distributions of temperature, heat flux, species concentration, current density and saturation are found to be highly oscillating in nature between the local rib and channel locations. Furthermore, the higher the compression ratio, the better is the cell performance and the larger is the fluctuation amplitude. Finally, the higher the compression ratio, the more are the saturation, water flooding and hydrogen deficiency downstream. More detail compression effects on membrane conductivity, etc, are also presented.
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