USE OF TEXTURED SURFACES FOR CONDENSATION OF WATER VAPOUR AND MIST

Abstract

Producing purified water from air moisture is feasible even in arid areas where humidity is intermittent. This method relies on a condenser, usually cooler than the surroundings, where water condenses. Many studies use materials with diverse hydrophobicity, making it hard to pinpoint surface effects on condensation. Thus, comparing hydrophobic and hydrophilic surfaces with identical textures is crucial. The aim of this work is to determine the effect of gyrophobic metal surfaces on the processes of water collection from steam. Experiments in this work were conducted in a close chamber in the environment of water fog produced by the fog machine at the room temperature. It was shown that hydrophilic surfaces enhance water vapor condensation efficiency by up to 38% compared to hydrophobic ones. In this work, the femtosecond laser treatment was used to produce channel-shaped textures with a truncated trapezoidal cross-section, measuring 15 µm at the upper base, 45 µm at the lower base, and 22 µm in height. These textures were further extended by the development of aluminum oxide crystal inlays, ranging from 30-60 nm, due to metal oxidation from the laser's high-temperature interaction. Extended exposure to these textures in room environment naturally increases their water repellency. Contact angles can reach 148°, nearing the 154° efficiency achieved with stearic acid treatment. However, heating to 380 °C eliminates the hydrophobic layers, resulting in complete hydrophilisation. Textured hydrophilic surfaces prove most effective for condensate collection, outperforming hydrophobic surfaces by up to 28%. Additionally, microtexture orientation matters: a vertical orientation boosts condensate collection by 34% compared to horizontal orientation. The results may be useful in the development of water harvesting equipment for naturally dry regions, or place where extensive water purification is required.