Experimental investigation on the freezing characteristics of a droplet impacting a cold surface

Freezing after droplets impact cold surfaces is very common in real-life and industrial applications. In this study, via experimental methods, the freezing characteristics of a water drop impacting a supercooled substrate are studied. Effects of the Weber number and surface supercooling on the freezing diameter, freezing height, and freezing time are analyzed, respectively. Interestingly, both the freezing diameter and the freezing height are closely dependent on the We number, whereas they are independent of the surface temperature, due to the inertial force playing a leading role in the dynamic process of the impact droplet. While the freezing time is affected by the surface temperature and the Weber number. For small Weber numbers at We = 3.6–21.8, the freezing time drops with the decrease in surface temperature; while for large Weber numbers at We = 21.8–109.1, the influence of surface temperature on the contact time can be ignored. Based on this, a quantitative relationship between these freezing parameters and the impact Weber number is preliminarily established. This study will reveal the coupling mechanics of impact dynamic and freezing dynamic and quantitatively calculate the freezing characteristics, guiding the design of anti-icing surfaces.