VISUALIZATION RESEARCH OF DROPLET FREEZING ON AN INCLINED TITANIUM SURFACE

Abstract

Freezing of droplets on inclined cold surfaces was investigated through their visualization. A DSA100 Droplet Surface Analyzer was employed to study the effects of surface tilt angle and temperature on the phase transition time of droplets of various sizes. The post-freezing contact diameter and contact angle between the droplets and the titanium surface were measured and analyzed. From these experimental studies and the related analysis it appears that the freezing time of droplets on cold surfaces at different tilt angles (15°, 30°, 45°, 60°, 75°, and 90°) is the longest when the bottom plate is tilted at 45°. As the tilted surface temperature is reduced, the droplet shape as it froze hardly changes with increasing tilt angle, and at the same time the freezing time of the droplets at each inclination angle is further reduced with decreasing bottom plate temperature. The experiments show that the deformation of a freezing 20-μL droplet on an inclined cold surface is more pronounced than that of a 1-μL droplet. The phase transition time of a large-volume droplet also decreases as the cold plate inclination increases. Thermodynamic equations are also employed to explain the longest droplet phase transition time which occurs at an inclination of 45°.