Evaporation characteristics of water droplets on heated surfaces with various coatings and under different wall thermal conditions

The anti-ice system is a crucial subsystem for ensuring aircraft safety. Water droplet evaporation on its surface is a frequent occurrence during flight. Investigating the characteristics of water droplet evaporation is essential for designing effective active or passive aircraft anti-ice systems. Previous research has primarily focused on the evaporation of small droplets under constant wall temperature conditions. The emergence of more electric aircraft has led to the adoption of electrical heating anti-ice systems, which typically operate under conditions of constant wall heat flux. Despite this shift, the quantitative characteristics of evaporation under different surface properties and constant wall heat flux conditions have not been thoroughly investigated. In this paper, an experimental test site was built to study the evaporation characteristics of water droplets on heating surfaces with various coatings and under different wall thermal conditions. The experimental results showed that the evaporation time for droplets on hydrophobic surfaces was longer than that on hydrophilic surfaces. The increase in evaporation time ranged from 5 to 13 times as the surface temperature was raised from 40 °C to 80 °C. Furthermore, the difference in evaporation time between small and large droplets was more pronounced under constant temperature conditions than that of constant heat flux conditions. For droplets on polished aluminum and hydrophilic surfaces, the evaporation rate was linearly related to the evaporation surface area. The findings of this study can inform future optimizations of anti-ice systems.