Tranter T G, Gostick J T, Burns A D, Gale W F
Department of Chemical Engineering, University of Waterloo, 200 University Ave. W, Waterloo, ON USA.
2Centre for Integrated Energy Research, University of Leeds, Leeds, LS2 9JT UK.
Transp Porous Media. 2018;121(3):597-620. doi: 10.1007/s11242-017-0973-2. Epub 2017 Dec 1.
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.
采用基于Voronoi图方法的随机孔隙网络模型，模拟了中性润湿性纤维介质的饱和度与毛细管压力曲线中的滞后现象。该网络经过校准，以拟合收集到的用于燃料电池气体扩散层的碳纤维纸的实验气-水毛细管压力数据。这些材料表现出异常强烈的毛细管滞后现象，以至于水的注入和抽出分别发生在正、负毛细管压力下。在不需要引入接触角滞后的情况下，当使用基于穿过环形中心的弯月面曲率的孔隙尺度模型时，这种毛细管行为得以重现。经典的沃什伯恩关系式被证明会产生错误结果，在对纤维介质进行建模时不建议使用。还针对水的注入和抽出情况，研究了饱和度分布对介质有效扩散率的重要影响。这些发现有助于理解纤维介质中的毛细现象和燃料电池设计。
