Moist air condensation is of significant scientific and societal interest especially for harvesting potable water from atmospheric air. Dropwise condensation of water vapor present in moist air is preferred when compared to filmwise condensation because of high transport coefficients that augment condensation rate of the distillate. The efficacy and sustainability of dropwise condensation depends on various operating parameters, for instance, temperature of moist air, relative humidity, subcooling of the substrate, thermophysical properties of moist air and physico-chemical properties of the condensing substrate. In this context, a mathematical model of dropwise condensation of moist air over a textured surface has been developed in the present work. Jointly, an experimental study of moist air condensation over a specially prepared superhydrophobic surface has been carried out for model validation. By suitably deriving the correction factor for the interfacial resistance to account for the presence of noncondensable gases, good agreement has been obtained between the model and experiments. Thereafter, simulations have been performed over a range of conditions from the viewpoint of maximizing the condensate output. Results of the study show that a vertical substrate with a high equilibrium contact angle and low contact angle hysteresis increases drainage of water drops. Hence, there is an increase in the water productivity of the surface. In addition, the condensation rate increases with increase in relative humidity, degree of subcooling and saturation temperature of moist air. The results of the study can be utilized towards designing devices for water harvesting from the atmosphere.

湿空气凝结具有重大的科学和社会意义，尤其是从大气中收集饮用水时。与膜状冷凝相比，存在于湿空气中的水蒸气的逐滴冷凝是优选的，因为高传输系数会增加馏出物的冷凝速率。逐滴冷凝的功效和可持续性取决于各种操作参数，例如，潮湿空气的温度，相对湿度，基材的过冷度，潮湿空气的热物理性质以及冷凝基材的物理化学性质。在这种情况下，在本工作中已经开发了湿空气在有纹理的表面上逐滴冷凝的数学模型。共同，进行了在特殊制备的超疏水表面上的湿空气凝结的实验研究，以进行模型验证。通过适当地推导界面电阻的校正因子以解决不凝性气体的存在，在模型和实验之间已经获得了良好的一致性。此后，从最大化冷凝水输出的角度出发，已经在一系列条件下进行了模拟。研究结果表明，具有高平衡接触角和低接触角滞后性的垂直基板会增加水滴的排水。因此，增加了表面的水生产率。另外，冷凝率随着相对湿度，过冷度和湿空气饱和温度的增加而增加。