Hysteresis in the saturation versus capillary pressure curves of neutrally wettable fibrous media was simulated with a random pore network model using a Voronoi diagram approach. The network was calibrated to fit experimental air-water capillary pressure data collected for carbon fibre paper commonly used as a gas diffusion layer in fuel cells. These materials exhibit unusually strong capillary hysteresis, to the extent that water injection and withdrawal occur at positive and negative capillary pressures, respectively. Without the need to invoke contact angle hysteresis, this capillary behaviour is re-produced when using a pore-scale model based on the curvature of a meniscus passing through the centre of a toroid. The classic Washburn relation was shown to produce erroneous results, and its use is not recommended when modelling fibrous media. The important effect of saturation distribution on the effective diffusivity of the medium was also investigated for both water injection and withdrawal cases. The findings have bearing on the understanding of both capillarity in fibrous media and fuel cell design.

中文翻译：

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中性可湿性纤维介质中的毛细管滞后：燃料电池电极的孔隙网络研究

中性可湿性纤维介质的饱和度与毛细管压力曲线的滞后是通过使用 Voronoi 图方法的随机孔隙网络模型来模拟的。该网络被校准以适合为通常用作燃料电池中的气体扩散层的碳纤维纸收集的实验空气-水毛细管压力数据。这些材料表现出异常强的毛细管滞后，以至于分别在正和负毛细管压力下注水和取水。无需调用接触角滞后，当使用基于通过环形中心的弯液面曲率的孔隙比例模型时，这种毛细管行为会重新产生。经典的 Washburn 关系被证明会产生错误的结果，并且在对纤维介质建模时不推荐使用它。饱和度分布对介质有效扩散率的重要影响也针对注水和取水情况进行了研究。这些发现对理解纤维介质中的毛细作用和燃料电池设计都有影响。