Freezing of supercooled water drops on cold solid substrates: initiation and mechanism

Abstract

Drops of liquid are placed on substrates having temperatures below the melting point of the liquids (supercooling). All well-known stages of cooling and freezing (supercooling-recalescence-main solidification-ice cooling) of water drops on both hydrophilic and hydrophobic surfaces were observed using a k-type thermocouple and an IR camera. Duration of the main solidification and the ice cooling stages were found to be dependent on the drop size. However, no conclusive relationship can be made regarding the duration of the supercooling stage with the drop size and the surface hydrophobicity. Using an IR camera, we observed that the solidification initiation of the main drop, which corresponds to the supercooling stage duration, is triggered by the erratic wave-like recalescence front of the surrounding condensed microdrops. The nucleation always initiates from the trijunction and propagates into the drop volume with different structural morphologies determined by temperatures and surface hydrophobicity of the substrate. The recalescence front speed of the main drop varies from 50 to 150 mm/s with supercooling temperatures.

Ice nucleation behaviour on sol–gel coatings with different surface energy and roughness

“…There have been quite some debates about the initiation site of nucleation. Some authors [48][49][50] suggested that the nucleation preferentially starts at the three-phase contact line, while others 51,52 claimed that it starts randomly at the whole solid-liquid interface. The controversy might be caused by different test environment or Such a nucleation rate is plotted in Fig.…”

Drop spreading and gelation of thermoresponsive polymers

“…For freezing-induced pinning, the literature offers various hypotheses for the criterion for contact line arrest [5][6][7][11][12][13]. For example, the delay in the arrest was argued to be caused by the requirement for a critical nucleus to form near the contact line [11,12]. However, a detailed description of growth of the nucleus in the presence of flow is lacking.…”

“…Arrest of the drop can be due to temperature-dependent viscosity (generally diverging when approaching the melting point), or more dramatically due to solidification near the liquid/solid interface. Such cases were investigated for droplet impact [5][6][7][8]10], as well as for spontaneous spreading after gentle deposition on solid substrates [11][12][13]. Inkjet printing and applications such as spray coating indeed involve droplet impact.…”

Overhanging shapes of freezing sessile drops under continuous liquid supply

“…Their study was focused on the arrest and spreading criterion of the puddle at the contactline, and found a pinning criterion based on a threshold value for the contact angle between the liquid and the basal solid. Another study revisited the pinning criterion in terms of critical frozen volume near the triple line 17 . More recently, a kinetic criterion based on the advancing velocity of a spreading drop was quantitatively and successfully tested 9 .…”