Effects of porosity distribution variation on the liquid water flux through gas diffusion layers of PEM fuel cells
Effects of porosity distribution variation on the liquid water flux through gas diffusion layers of PEM fuel cells
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DOI：
10.1016/j.jpowsour.2006.02.060
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发表时间：
2006-10
影响因子：
9.2
通讯作者：
Z. Zhan;Jinsheng Xiao;Dayong Li;M. Pan;R. Yuan
中科院分区：
文献类型：
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作者：
Z. Zhan;Jinsheng Xiao;Dayong Li;M. Pan;R. Yuan
膜电极组件(MEA)的泛洪和聚合物电解质膜的脱水一直是聚合物电解质膜燃料电池(PEMFCs)需要解决的关键问题。到目前为止，几乎没有发表的论文集中在不同结构的气体扩散层(GDLS)中的液态水通量的研究。对于具有均匀孔隙度、孔隙度变化(GDL和微孔层(MPL))和梯度变化孔隙度的气体扩散层，采用一维模型，基于固定液水流过GDL的假设，分析了液体饱和度分布。在假定催化层/GDL和GDL/气路界面的液体饱和度差不变的基础上，计算了液态水通过GDL的通量。结果表明，在稳态条件下，液态水通量随接触角和气孔率的增大而增大，随气孔层厚度的减小而增大。当MPL被放置在催化层和GDL之间时，液体饱和度在MPL和GDL之间重新分布。这提高了液态水的排水性能。随着MPL孔隙率的增加和MPL厚度的减小，液态水通过GDL的通量增加。当气液两层总厚度保持不变，当液膜厚度减至3μm时，液水通量显著增加，即膜外液膜难以驱替。具有孔隙度梯度的GDL更有利于液态水从催化层向气路中排放；对于等效孔率相同的GDLS，梯度越大，液态水越容易排出。在计算实例中，线性孔隙率为0.4X+0.4的GDL是最好的。
Flooding of the membrane electrode assembly (MEA) and dehydrating of the polymer electrolyte membrane have been the key problems to be solved for polymer electrolyte membrane fuel cells (PEMFCs). So far, almost no papers published have focused on studies of the liquid water flux through differently structured gas diffusion layers (GDLs). For gas diffusion layers including structures of uniform porosity, changes in porosity (GDL with microporous layer (MPL)) and gradient change porosity, using a one-dimensional model, the liquid saturation distribution is analyzed based on the assumption of a fixed liquid water flux through the GDL. And then the liquid water flux through the GDL is calculated based on the assumption of a fixed liquid saturation difference between the interfaces of the catalyst layer/GDL and the GDL/gas channel. Our results show that under steady-state conditions, the liquid water flux through the GDL increases as contact angle and porosity increase and as the GDL thickness decreases. When a MPL is placed between the catalyst layer and the GDL, the liquid saturation is redistributed across the MPL and GDL. This improves the liquid water draining performance. The liquid water flux through the GDL increases as the MPL porosity increases and the MPL thickness decreases. When the total thickness of the GDL and MPL is kept constant and when the MPL is thinned to 3μm, the liquid water flux increases considerably, i.e. flooding of MEA is difficult. A GDL with a gradient of porosity is more favorable for liquid water discharge from catalyst layer into the gas channel; for the GDLs with the same equivalent porosity, the larger the gradient is, the more easily the liquid water is discharged. Of the computed cases, a GDL with a linear porosity 0.4x+0.4 is the best.