In previous macroscopic average models of proton exchange membrane fuel cells (PEMFCs), liquid water was assumed to be continuous throughout the carbon paper. The transport of disconnected water drops in carbon paper has long been neglected in these models, which tend to underestimate water saturation in carbon paper. This study proposes a two-phase flow model that considers the transport of disconnected water drops to simulate the air-water transport in carbon paper. The proposed model was established based on the relationship between capillary force and liquid water saturation, and this relationship was obtained by conducting centrifuge experiments. In the centrifuge experiment, initially, the water saturation inside the carbon paper sample was one, and the centrifugal acceleration was zero. As the centrifugal acceleration increased, the water saturation decreased owing to the centrifugal force. After twenty seconds, the water saturation no longer decreases because the centrifugal force on the liquid water is balanced by the capillary force. Centrifugal acceleration was used to evaluate the capillary force. When the centrifugal acceleration was 185 , the saturation of the water drops in the balanced state was 32.0%. As the centrifugal acceleration increases to 739 , the saturation decreases to 6.5%. According to the experimental results, a function correlating the saturation and centrifugal acceleration, that is, the capillary force, was established. Finally, the results show that the centrifugal acceleration is more than 18.5 times that of the gravitational acceleration, indicating that the effect of gravity on the motion of water drops is negligible.

中文翻译：

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借助离心实验测量和模拟碳纸中液态水的传输

在之前的质子交换膜燃料电池（PEMFC）宏观平均模型中，液态水被假设在整个碳纸中是连续的。这些模型长期以来一直忽略碳纸中不连续水滴的传输，这往往会低估碳纸中的水饱和度。本研究提出了一种两相流模型，考虑不相连的水滴的传输，以模拟碳纸中的空气-水传输。该模型是根据毛细管力与液态水饱和度之间的关系建立的，并且该关系是通过离心实验获得的。在离心实验中，最初碳纸样品内部的水饱和度为1，离心加速度为零。随着离心加速度的增加，由于离心力的作用，水饱和度降低。二十秒后，水饱和度不再降低，因为液态水的离心力与毛细管力平衡。使用离心加速度来评估毛细管力。当离心加速度为185 时，平衡状态下水滴的饱和度为32.0%。随着离心加速度增加到 739 ，饱和度降低到 6.5%。根据实验结果，建立了饱和度与离心加速度的相关函数，即毛细管力。最后结果表明，离心加速度是重力加速度的18.5倍以上，表明重力对水滴运动的影响可以忽略不计。