A modeling study on freezing characteristics of sessile and pendant water droplets on cold plate surfaces

Abstract

The freezing phenomena of sessile and pendant water droplets on horizontal and inverted surfaces are widespread in industrial fields, which always causes great structural destruction and energy waste. Considering the gravity effect on the droplet profile, a theoretical model is developed to calculate the freezing characteristics of sessile and pendant droplets and experimentally verified. The average deviation of the model in the droplet freezing time is 10.53 % and the determination coefficient in the droplet profile is above 98 %. Based on the model, the freezing characteristics of sessile and pendant droplets under different water droplet volumes (characterized by the Bond number, Bo), contact angles and cold plate temperatures are investigated. When Bo ≤ 1, there is almost no difference in the freezing characteristics of sessile and pendant droplets. When Bo > 1, obvious differences are observed with a pendant droplet having a higher height and a longer freezing time. For both sessile and pendant droplets, the freezing height is approximately proportional to the initial height with the sessile droplet yielding a smaller proportion coefficient. Their freezing times can be written as a function of the Bond number, contact angle and cold plate temperature. Under the same condition, the ratio of freezing time by the pendant droplet to that by the sessile one is scaled as Bo1/4 when Bo > 1. The findings in this study help better understand the freezing characteristics of the sessile and pendant droplets and thus optimize anti-icing and anti-frosting technologies.