Dependence of wettability of microtextured wall on the heat and mass transfer: Simple estimates for convection and heat transfer

Heat exchange of the evaporating water drop located on the structured wall is investigated experimentally. Heat and mass transfer enhancement by structures in a wide range of cavities' diameters from 50 mu m to 2.2 mm is analyzed. Cavities are created in two ways: mechanical treatment of the wall and laser action. The behavior of the heat flux and heat transfer coefficient on the textured surface is compared with the rough (unstructured) wall. The effect of wettability on heat transfer (transition from superhydrophilic to superhydrophobic wall) is investigated. The most pronounced is the intensification of convection and heat transfer for the largest investigated cavities with a diameter of 2.2 mm, as well as for the textured superhydrophilic wall with a cavity diameter of 50 mu m. Thermal imaging measurements show a non-uniform temperature field in the drop in the presence of cavities. The data obtained are valuable for optimizing heat exchangers with textured surfaces when evaporating sessile droplets increase heat transfer from heated surfaces.