Experimental investigation on impact dynamics and freezing performance of water droplet on horizontal cold surface

Abstract

Freezing of impinged water droplet on cold surface plays a negative role in energy conservation. Morphology evolutions of the droplet impact and freezing processes are recorded from top and side views through the high-speed photography. Effects of release height and surface temperature on impact dynamics and freezing performance of water droplet on horizontal cold surface are analyzed. The experimental results indicate that the maximum spreading factor increases and the oscillation time decreases with increasing release height. When the surface temperature is in the range of −15 to −20 °C, with reducing surface temperature, the maximum spreading factor decreases, the retraction ratio increases, while the oscillation time changes barely. However, the maximum spreading factor decreases, the oscillation time increases, and the retraction ratio keeps constant with decreasing surface temperature when the surface temperature ranges from −25 to −30 °C. Besides, the freezing delay time is sensitive to the surface temperature, and it drops rapidly from hundreds of seconds to zero when the surface temperature reduces from −15 to −30 °C. For all the water droplets under the condition of this study, the freezing processes are within 7 s. This work is meaningful for understanding the microphysical characteristics of impinged droplet icing.