Unique dynamics of water-ethanol binary droplets impacting onto a superheated surface with nanotubes

Dependence of the impact dynamics of an water-ethanol binary droplet on a surface structured with titanium dioxide nanotubes is investigated on the surface temperature and ethanol concentration. Six regimes of droplet dynamics, namely contact boiling, film levitation, film boiling levitation, central-jet levitation, central-jet and Leidenfrost phenomenon have been found on the nanotube surface. Some regimes exhibit film levitation, a central-jet phenomenon, or a combination of them. Film levitation is mitigated at a higher surface temperature or ethanol concentration since a shorter contact time is resulted under such conditions. The vaporization of hemi-wicking liquid in nanotubes causing peripheral jets, and the vaporization of droplet bottom layer above the nanostructure are both reduced at a higher surface temperature or ethanol concentration. Central-jet of liquid is enhanced and then mitigated as the surface temperature or ethanol concentration increases, and the vanish of which represents the commence of Leidenfrost phenomenon. The surface nanostructure increases the Leidenfrost temperature, while increasing the ethanol leads to the opposite effect. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The impact dynamics of a water-ethanol binary droplet on a surface structured with titanium dioxide nanotubes is dependent on the surface temperature and ethanol concentration, resulting in six different droplet dynamics regimes. These regimes are influenced by surface temperature and ethanol concentration, with film levitation being mitigated at higher surface temperatures or ethanol concentrations.