Air humidity effects on water-drop icing.

Area of Science:

• Physics of Fluids
• Thermodynamics
• Materials Science

Background:

• The icing of water droplets on cold surfaces is a common phenomenon with implications in various fields.
• Previous models often overlook the influence of ambient atmospheric conditions on the icing process.

Purpose of the Study:

• To investigate the effect of atmospheric conditions, specifically air humidity, on the kinetics of the icing front and the formation of ice tips.
• To develop and validate a theoretical model that incorporates humidity effects for droplet icing.

Main Methods:

• Experimental observation of water droplet icing on a cold substrate under controlled humidity.
• Theoretical modeling using a modified Stefan model that accounts for humidity-induced phase changes and heat transfer.

Main Results:

• Air humidity was found to induce significant liquid-vapor phase change at the droplet interface.
• The associated heat transfer strongly influences both the speed of the icing front and the final shape of the iced drop, including tip formation.
• The modified Stefan model showed good agreement with experimental data for front kinetics and tip angle.

Conclusions:

• Atmospheric humidity is a critical factor in water droplet icing dynamics.
• A humidity-inclusive Stefan model accurately predicts experimental observations of icing kinetics and morphology.
• Understanding these effects is crucial for applications involving freezing phenomena.