Study on Freezing Characteristics of Supercooled Water Droplets Impacting on Solid Surfaces

An experimental study was carried out to investigate the freezing characteristics of supercooled water droplets impacting on solid surfaces. Each water droplet was supercooled on the inside surface of a waterrepellent guideway in a cooled air environment and then blasted horizontally by a jet of pressurized cooled air to impact on the vertical surface of a test block. The deformation and freezing of the droplets were observed using a high-speed camera. The droplets were frozen under varying conditions of air temperature, surface temperature, impact velocity and droplet volume. The results indicated that the freezing behavior of a droplet was strongly affected by the condition of the solid surface. Further, the results revealed that the supercooling solidification process consisted of two steps with two greatly different time scales. Finally, it was shown that the freezing behavior of an ice layer was affected by the presence of a liquid-like thin film.