Effect of surface characteristics on condensate droplets growth

•Four surfaces with different characteristics were prepared by chemical etching.•Micro-nano structures of the surfaces were tested by SEM.•Condensation behavior of droplets on the surfaces were observed.•Shape and distribution density of droplets were investigated by microscopy.•Radius and surface coverage of droplets were quantitatively calculated and analyzed. In order to explore effective methods for frost restraint, the effect of surface characteristics on the growth of condensate droplets in the early stage of frosting was investigated. Aluminium surfaces with four types of characteristics (hydrophilic, baseline, hydrophobic and superhydrophobic surfaces) were prepared by chemical etching. The surface micro-nano structure and contact angle were measured by scanning electron microscope (SEM) and contact goniometer. Combined with surface energy and droplets distribution density theory, the shape, occurrence time and distribution density of the condensate droplets on different surfaces were examined and analyzed by visual condensation experimental system at different surface temperatures. The results showed that at the same surface temperature, condensate droplets were formed, in time sequence, on hydrophilic surface first, and then on the baseline, hydrophobic, superhydrophobic surface. Droplets on the superhydrophobic surface and the hydrophobic surface were spherical. The superhydrophobic surface with the distributed droplets was sparser than the hydrophobic surface. The distribution of condensate droplets on the baseline surface was dense and the drpolets were in tortoise shell shape. The condensate droplets on the hydrophilic were spread more uniformly, and covered almost the entire surface. Based on nucleation formation and statistical, the radius and surface coverage of condensate droplets on different surfaces were determined and analyzed at different surface temperatures. The results indicate that the condensate droplets on superhydrophobic surface had the smallest radius and the lowest coverage in comparison with all other surfaces.