Evolution of droplet freezing front and surface temperature on cold surface under forced convection

Abstract

The evolution of freezing front and surface temperature in droplet freezing process under forced convection condition was studied. The influence mechanism of convective heat transfer on the droplet freezing front was explored through the surface temperature change. A prediction model for droplet freezing under forced convection was established by considering the effect of convective heat transfer. The results indicated that in the peak freezing mode, the rise of the freezing front is driven by the heat conduction of the cold surface, while in the peakless freezing mode, the freezing front will reach thermal equilibrium, and its movement is driven by the frost induced inter-droplet nucleation. Affected by the force-convective heat transfer, the temperature difference inside the droplet increases significantly. The higher droplet surface temperature on the windward makes the freezing front and isotherm tilt towards the windward. As airflow velocity increase, the larger convective heat transfer leads to slower temperature decrease in the solidification stage. By analyzing the freezing front moving process on the windward and leeward separately, the evolution of the freezing front and solidification time can be predicted accurately by the model for the peak freezing mode, and the calculated critical criterion for freezing mode transition agrees well with the experimental results.