Nucleation enhancement by energy dissipation with the collision of a supercooled water droplet

Abstract

Lack of knowledge on nucleation with mechanical disturbances hinders researchers in understanding the anti-icing properties of superhydrophobic surfaces. In this research, experiments are designed to observe the freezing process of a supercooled water droplet at −14 °C with different levels of external disturbances by changing the impact velocity, and the nucleation rates are statistically analyzed. It is found that compared with the static state, the nucleation rates of droplets during the collision increase by three and five orders of magnitude on the hydrophilic epoxy resin and superhydrophobic polytetrafluoroethylene (PTFE) surfaces, respectively, which leads to a much higher instantaneous nucleation rate on the superhydrophobic surface than on the hydrophilic surface. Then, the mechanical energy dissipation during the impact is analyzed. The logarithm of the nucleation rate is approximately linear in relation to the logarithm of the average energy dissipation rate, while the nucleation rate of the rough PTFE surface increases more rapidly than that of the other smooth surface. Finally, the effect of the energy dissipation on the nucleation energy barrier is discussed theoretically and an impact-nucleation model is proposed, which drives the reconsideration of the design of a superhydrophobic anti-icing coating.