Enhancing dropwise condensation of vapor from moist air over a copper substrate by temperature-controlled chemical etching

Surface engineering of copper substrates for condensation of vapor in moist air in an atmospheric water generator (AWG) is an intensive area of research. The goal here is to enhance the vapor condensation rate, thus yielding a large quantity of potable water. In the present study, three scalable chemical processes such as deposition, etching, and etching with deposition have been explored for preparation of the copper substrate. In these processes, polished copper substrates are dipped in select chemical solutions for appropriate periods of time and temperature. The resulting surface morphology as well as surface chemistry has been characterized using SEM and EDS analysis. In addition, surfaces are characterized in terms of hydrophobicity with respect to water. Moist air condensation experiments have been carried out on the proposed substrates for estimating their performance in terms of vapor condensation from atmospheric air. Results show that the water collection rate at relative humidity of 90% and degree of sub-cooling at 6 °C achieved for the ‘ea’, substrate is as high as 1.2 l/m2-h; it is 1.4 l/kWh with respect to the power expended to maintain a low surface temperature. The surface efficacy is improved by 63% on the ‘ea’ substrate and 16% on the ‘e2’ substrate with respect to a clean polished copper surface. These results are validated against simulations from a time-dependent dropwise condensation model. It founded that the superhydrophobic copper substrate prepared as per the stated methodology serves as an improved surface for condensation of water vapor present in moist air.