Freezing property of a droplet impacting supercooled hydrophilic surfaces

The impact and freezing of a droplet on a cold surface is a ubiquitous phenomenon in engineering processes. In this study, the freezing profile and freezing time of a droplet impacting a cold silicon surface are employed by experimental methods. The influences of the impact of Weber number (We) and surface temperature (Ts) on the freezing properties, including freezing diameter/height and the freezing time (tf), are examined. Results indicate that while the freezing profile is primarily influenced by the Weber number rather than the surface temperature, the freezing diameter exhibits a linear relationship with We1/4, and the freezing height decreases as the Weber number increases due to the dominance of inertial forces during spreading. Heat transfer between the droplet and the surface, along with its effect on viscous dissipation energy, plays a relatively minor role. However, both surface temperature and the Weber number significantly affect freezing time. Freezing time decreases markedly with decreasing surface temperature. With increasing Weber number, freezing time initially decreases and then plateaus. The relationship between freezing time and Weber number can be expressed as We−0.73≤tf ≤ We−0.52 at Ts = −15 to −30 °C. This work elucidates the coupling mechanics of impact dynamics and freezing dynamics, providing a theoretical foundation for quantifying icing characteristics.