Three typical icing patterns: Competition between the drop dynamics and heat transfer

Abstract

Icing of supercooled drops on solid surfaces is common in nature and plays an important role on the energy and transportation field. In this paper, the experimental study and theoretical analysis are performed to investigate the freezing characteristics of supercooled drops impacting on solid surfaces. Three icing patterns, crater-like (t_delay < t_spread), pancake-like (t_spread < t_delay < t_retraction), and peak-like (t_delay > t_retraction) are found in the experimental results. The coupling mechanism between drop dynamics and heat transfer under different icing patterns is revealed in detail. During the spreading and retraction processes, the convective heat transfer is dominant between the moving liquid lamella and the solid wall. While, the thermal conduction dominates the heat transfer mode between the static drop and the solid wall after the retraction process. In particularly, a theoretical model to predict the nucleation delay time is proposed through the modified heat transfer coefficient, which is in good agreement with the experimental results. The critical criterion for three collisional icing patterns of supercooled drops is also derived as a function of the Weber number We, the Reynolds number Re, and the dimensionless temperature Θ. This work provides a theoretical basis for predicting the collisional freezing of supercooled drops in the anti/de-icing field.