Session: 5.1.1 - Advanced thermal-flow diagnostic techniques - I

Paper Number: 165896

165896 - Dynamic Random Freezing Phenomena and Nucleation Rates of Supercooled Water Droplets Colliding With Cold Surfaces 

Abstract: 

In the present work, an experimental investigation of supercooled water droplets impacting superhydrophobic substrates was conducted at a substrate temperature of -10 °C, while the droplet temperature was maintained at -10 °C as well. Over a hundred repeated experiments were performed to observe the behavior of the supercooled droplets upon impact. The results consistently demonstrated that ice nucleation occurred randomly as the supercooled droplets struck the cold substrate. This stochastic ice nucleation, coupled with the subsequent dendritic ice growth, had a pronounced effect on the dynamics of droplet impact, spreading, and rebound. Notably, the nucleation sites were invariably found near the center of the impact area on the substrate across all experimental trials. Utilizing a novel analytical method, the nucleation rate during the impact process was quantified and revealed to be 270,000 times greater than that observed for a static supercooled water droplet at the same temperature and on an identical substrate. This substantial increase in the nucleation rate is likely due to the intense perturbations induced by the impact forces and the dynamic transition of the droplet wetting behavior from the Cassie to the Wenzel state. This study is the first to document the random freezing phenomena of impacting supercooled water on a superhydrophobic surface and provides an experimental quantification of the nucleation rate during the dynamic impact process. The findings contribute to a deeper understanding of the complex interplay between supercooled water droplets and superhydrophobic surfaces, which has implications for a range of applications, including anti-icing technologies and microfluidic devices.

Presenting Author: Min Chen Tsinghua University

Presenting Author Biography: Dr. Min Chen is a Professor in the Engineering Mechanics Department at Tsinghua University, China. He received his Ph.D. from Xi’an Jiaotong University, China, in 1997, and joined Tsinghua University in 1998. He has been a Visiting Scholar at the Massachusetts Institute of Technology, USA, in 2002, and an Alexander von Humboldt Research Fellow at the University of Stuttgart, Germany, from 2003 to 2004. His current areas of interest include experimental and molecular dynamics studies of interphase transport and phase change, micro-nano-fluidics, and aircraft anti-icing technologies. He has authored and co-authored more than 180 technical publications.