Effects of superheat degree and wettability on droplet evaporation time near Leidenfrost point through Lattice Boltzmann simulation

Abstract The evaporation of droplet on a superheated surface is a very important and common phenomenon in industrial production, such as spray cooling and metallurgical treatment. In this paper, a two-dimensional numerical simulation based on Lattice Boltzmann Method has been adopted to analyze the evaporation behavior of liquid droplet on an over-heated surface. The effects of superheat degree (Ja number) and surface wettability on droplet evaporation are analyzed respectively. During the evaporation process, the evaporation pressure at the bottom of the droplet exhibits periodic oscillation corresponding to bouncing movement. The oscillation gradually decays in the case of low Ja numbers, but for high Ja numbers, the oscillation doesn't decay. Leidenfrost vapor layer is more likely to be generated on a hydrophobic surface. Meanwhile, the comprehensive influence of wettability and Ja number on droplet evaporation time was studied systematically. On hydrophilic surfaces, there is a critical Ja value, around which the evaporation time exhibits a U-type tendency. However, the evaporation time continues to decrease as Ja number increases on hydrophobic surfaces.