Wetting of surfaces with porous coating is relevant for a wide variety of technical applications, such as printing technologies and heat transfer enhancement. Imbibition and evaporation of liquids on surfaces covered with porous layers are responsible for significant improvement of cooling efficiency during drop impact cooling and flow boiling on such surfaces. Up to now, no reliable model exists which is able to predict the kinetics of imbibition coupled with evaporation on surfaces with porous coatings. In this work, we consider one of possible mechanisms of imbibition on a substrate covered by a nanofiber mat. This is the capillary pressure-driven flow in a corner formed between a flat substrate and a fiber attached to it. The shape and the area of the cross-section occupied by the liquid as well as the capillary pressure change along the flow direction. A theoretical/numerical model of simultaneous imbibition and evaporation is developed, in which viscosity, surface tension and evaporation are taken into account. At the beginning of the process the imbibition length is proportional to the square root of time, in agreement with the Lucas-Washburn law. As the influence of evaporation becomes significant, the imbibition rate decreases. The model predictions are compared with experimental data for imbibition of water-ethanol mixtures into nanofiber mat coatings.

用多孔涂层润湿表面与多种技术应用有关，例如印刷技术和增强热传递。液体在多孔层覆盖的表面上的吸着和蒸发可显着改善液滴撞击冷却和此类表面上的沸腾过程中的冷却效率。迄今为止，尚无可靠的模型能够预测吸水性以及多孔涂层表面蒸发的动力学。在这项工作中，我们考虑了在纳米纤维垫覆盖的基材上吸收的一种可能机制。这是毛细管压力驱动的流动，该流动是在平坦基材和与其相连的纤维之间形成的一个角上。液体所占横截面的形状和面积以及毛细压力会沿着流动方向发生变化。建立了同时吸收和蒸发的理论/数值模型，其中考虑了粘度，表面张力和蒸发。在该过程的开始，吸水长度与时间的平方根成正比，这与卢卡斯-沃本法则一致。随着蒸发的影响变得显着，吸水率降低。将模型预测值与水-乙醇混合物吸收到纳米纤维毡涂层中的实验数据进行比较。在过程的开始，吸水长度与时间的平方根成正比，这与卢卡斯-沃什本定律一致。随着蒸发的影响变得显着，吸水率降低。将模型预测值与水-乙醇混合物吸收到纳米纤维毡涂层中的实验数据进行比较。在该过程的开始，吸水长度与时间的平方根成正比，这与卢卡斯-沃本法则一致。随着蒸发的影响变得显着，吸水率降低。将模型预测值与水-乙醇混合物吸收到纳米纤维毡涂层中的实验数据进行比较。