Icing characteristics of supercooled sessile water droplets on the top of cold micro-pillars

Abstract

Icing and frosting problems on cold surfaces affect the normal operation of equipment and optimizing the anti-icing and ice-phobic properties of structured surfaces needs exploration of the droplet icing process on typical micro-pillars. Based on the apparent heat capacity method, the icing characteristics of sessile water droplets on the top of cold micro-pillars are numerically studied with the supercooling degree considered. The effects of the micro-pillar diameter and height as well as the droplet volume and surface temperature are obtained. As the micro-pillar diameter becomes smaller, the icing rate of the droplet decreases and the freezing time increases. A higher micro-pillar enlarges the thermal resistance, slows down the movement of the freezing front, and results in an increase in the freezing time. The freezing time goes up as the droplet volume and the surface temperature increase. This changing trend becomes more conspicuous for a smaller micro-pillar diameter. Furthermore, the relationship between the freezing time and the micro-pillar diameter and height is derived from heat transfer analysis. The freezing time is negatively related to the square of the micro-pillar diameter. When the micro-pillar height increases one time, the droplet freezing time will increase by 3.42 %. The findings in this work give insights into the icing mechanism of supercooled sessile water droplets on the top of cold micro-pillars and provide references for the design and optimization of anti-icing and anti-frosting surfaces.