Experimental study on interaction between wettability configuration and dewing efficiency of surfaces with a cavity array

Abstract

Using condensed water produced by dewing to irrigate plants in desertification regions would greatly reduce the cost of water transport and optimize the use of water resources in arid and semi-arid areas. Modifying the microstructure and wettability arrangement can both enhance the rate of gas–liquid transition and dew production on surfaces of functional materials for water harvesting, that could further relieve pressures caused by water shortages. In this paper, interactions between dew productivity and the ratio of hydrophilic regions on the surface area, as well as the hydrophilic–hydrophobic boundary length of surfaces with a cavity array, have been investigated experimentally under conductive cooling. Furthermore, the weighted coefficient of the boundary length for dew productivity has been calculated. The results show the frequency of inter-droplet fusion – which dominates the speed of droplet growth – is governed by the number of hydrophilic–hydrophobic junctions, and the increase of dewing amount caused by the change of hydrophilic–hydrophobic boundary length is larger than that caused by the change of hydrophilic area. The largest dewing efficiency obtained in dewing experiment (298 K, 30% relative humidity) reaches 0.09 g cm⁻² h⁻¹. This indicates that currently, optimal dew productivities performed by water harvesting materials in test chambers will not be as efficient as those in desertification regions which characterized by low relative humidity.