Analysis of Water Transport in Proton Exchange Membranes Using a Phenomenological Model
Analysis of Water Transport in Proton Exchange Membranes Using a Phenomenological Model
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DOI：
10.1115/1.1895945
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发表时间：
2005-08
影响因子：
--
通讯作者：
P. Sui;N. Djilali
中科院分区：
文献类型：
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作者：
P. Sui;N. Djilali
对质子交换膜燃料电池膜上的水传输进行了研究，以进一步了解水管理问题和一个具有代表性的现象学模型的整体行为。该模型考虑了水通过电渗阻力和扩散的输运，采用一维等温系统的有限体积法求解。包括水的阻力系数、扩散系数和膜离子电导率在内的传输特性被表示为水含量和温度的函数。基于输运性质的一般形式，导出了解析解，并用来验证数值解的有效性。分析了物性变化对膜的水通量和膜整体质子电导率的影响。通过电渗透阻力和扩散传递之间的平衡不仅取决于操作条件，如膜边界的电流密度和相对湿度，而且还取决于设计参数，如膜厚度和膜材料。不同湿度边界条件下的水通量计算表明，对于厚膜(例如Nafion 117)，在广泛的操作条件下，电渗透阻力主导传输，而对于薄膜(例如Nafion 112)，水的扩散在特定的加湿条件和电流密度下变得同样重要。文中还讨论了基于CFD的质子交换膜燃料电池模型中膜传输问题的解决方法。编号：10.1115/1.1895945
An investigation of water transport across the membrane of a proton exchange membrane fuel cell is performed to gain further insight into water management issues and the overall behavior of a representative phenomenological model. The model accounts for water transport via electro-osmotic drag and diffusion and is solved using a finite volume method for a one-dimensional isothermal system. Transport properties including the water drag and diffusion coefficients and membrane ionic conductivity are expressed as functions of water content and temperature. An analytical solution based on a generalized form of the transport properties is also derived and used to validate the numerical solutions. The effects of property variations on the water flux across the membrane and on the overall membrane protonic conductivity are analyzed. The balance between transport via electro-osmotic drag and diffusion depends not only on operating conditions, such as current density and relative humidity at the membrane boundaries, but also on design parameters, such as membrane thickness and membrane material. Computed water fluxes for different humidity boundary conditions indicate that for a thick membrane (e.g., Nafion 117), electro-osmotic drag dominates the transport over a wide range of operating conditions, whereas for a thin membrane (e.g., Nafion 112), diffusion of water becomes equally important under certain humidification conditions and current densities. Implications for the resolution of membrane transport in CFD-based models of proton exchange membrane fuel cells are also discussed. DOI: 10.1115/1.1895945