Effect of asymmetric cooling of sessile droplets on orientation of the freezing tip

Anton Starostin; Vladimir Strelnikov; Leonid A Dombrovsky; Shraga Shoval; Oleg Gendelman; Edward Bormashenko

doi:10.1016/j.jcis.2022.04.019

Effect of asymmetric cooling of sessile droplets on orientation of the freezing tip

J Colloid Interface Sci. 2022 Aug 15:620:179-186. doi: 10.1016/j.jcis.2022.04.019. Epub 2022 Apr 9.

Authors

Anton Starostin¹, Vladimir Strelnikov¹, Leonid A Dombrovsky², Shraga Shoval³, Oleg Gendelman⁴, Edward Bormashenko⁵

Affiliations

¹ Institute of Technical Chemistry, Academician Korolev St, 3, Perm 614013, Russia.
² Chemical Engineering Department, Faculty of Engineering, Ariel University, P.O.B. 3, 407000 Ariel, Israel; X-BIO Institute, University of Tyumen, 6 Volodarskogo St, Tyumen 625003, Russia; Heat Transfer Department, Joint Institute for High Temperatures, 17A Krasnokazarmennaya St, Moscow 111116, Russia.
³ Department of Industrial Engineering and Management, Faculty of Engineering, Ariel University, P.O.B. 3, 407000 Ariel, Israel.
⁴ Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel. Electronic address: ovgend@technion.ac.il.
⁵ Chemical Engineering Department, Faculty of Engineering, Ariel University, P.O.B. 3, 407000 Ariel, Israel. Electronic address: edward@ariel.ac.il.

PMID: 35428001
DOI: 10.1016/j.jcis.2022.04.019

Abstract

Hypothesis: The shape of the "freezing tip" formed by the crystallization of water droplets demonstrated remarkable universality - no dependence on the cooling rate and physico-chemical properties of the substrate has been observed. At the same time, the spatial orientation of the freezing cone may be varied. We hypothesized that the orientation of the freezing tip is determined by the direction of heat flux at the base of the sessile droplet. This direction is expected to be changed when the substrate with a low thermal diffusivity is not cooled uniformly.

Experiments: We studied the freezing of water droplets placed on the inclined surface of wedges made from a variety of materials (polymers: Polymethylmethacrylate, Polytetrafluoroethylene, Polyurethane and metal: Titanium), which were cooled from below. The shape of the frozen droplets was controlled in situ.

Computations: The computational model was suggested for the transient temperature field in the polymer wedge to determine a time variation of the local heat flux under the droplets. A comparison of numerical results and the measurements enabled us to confirm the aforementioned hypothesis relating the orientation of the freezing tips to the direction of the heat flux.

Findings: It was established that the orientation of the freezing cone axis depends on the location of the frozen droplet on the inclined surface of the wedge. Calculations of the transient temperature field of the wedge confirmed our hypothesis about the physical reason of the various spatial orientations of the freezing cones.

Keywords: Asymmetric cooling; Freezing; Inclined plane; Tip singularity; Water droplets; Wetting.