Numerical analysis of the effect of ellipsoidal shape on the freezing behavior of impacting water droplets on cold surfaces

A two-dimensional numerical model that investigates the freezing behavior of ellipsoidal impacting water droplets on cold surfaces was established in this paper, focusing on the spreading behavior, impact force evolution and heat transfer behavior of ellipsoidal water droplets. For cold surfaces with a higher temperature, reducing aspect ratio can reduce the contact time of water droplets on the superhydrophobic surface, which is useful for the rebound of impacting water droplets. Increasing aspect ratio can increase the spreading range of water droplets, especially for hydrophilic surfaces. The evolution of impact force of ellipsoidal water droplets on superhydrophobic surfaces exhibits a double-peak feature. With increase of aspect ratio, the first peak of impact force is gradually decreased, while the second peak is gradually increased. The effect of surface wettability on the first peak of impact force is smaller. The feature of the second peak of impact force decreases with increase of surface wettability and finally disappears. Although water droplet with higher aspect ratio has smaller peak of heat transfer rate, the heat transfer between it and cold surface is greater than that with lower aspect ratio. The stronger the surface wettability, the more obvious this phenomenon is. For some applications where the rapid freezing of impacting water droplets is required, increasing aspect ratio of water droplets seems to be a good choice.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

A numerical model was established to investigate the freezing behavior of ellipsoidal water droplets on cold surfaces. The study focused on the spreading behavior, impact force evolution, and heat transfer behavior. The results showed that reducing the aspect ratio of the droplets reduced the contact time on superhydrophobic surfaces, facilitating rebound. Increasing the aspect ratio increased the spreading range, especially on hydrophilic surfaces. The impact force evolution on superhydrophobic surfaces exhibited a double-peak feature, with the first peak decreasing and the second peak increasing as the aspect ratio increased. The heat transfer between droplets and the cold surface was greater for higher aspect ratios, especially on more hydrophobic surfaces. Increasing aspect ratio seemed to be a good choice for rapid freezing applications.