Experimental study on the distribution and growth characteristics of trapped air bubbles in ice slices at different freezing temperatures

Icing is a phenomenon that exists widely in daily life and industry, and always brings some disadvantages. The dissolved air tends to become micro bubbles and trapped in ice, which have an effect on the physical properties of the ice. To explore the distribution and growth characteristics of trapped air bubbles in ice, experiments are carried out in a horizontal Hele-Shaw cell at different freezing temperatures. Results show that the trapped air bubbles in ice are classified into egg-shaped bubbles and needle-shaped bubbles according to an aspect ratio of bubble length to width larger and smaller than five. All the widths, lengths, and volumes of egg-shaped and needle-shaped bubbles increase with the distance from the cooler increasing and the freezing temperature decreasing. The length and volume of needle-shaped bubbles are larger than those of egg-shaped ones. The behaviors of trapped air bubbles are mainly affected by the freezing rate. When the bubble growth rate is greater than 20 μm/s, there are only egg-shaped bubbles in the ice, and when the bubble growth rate is less than 10 μm/s, there are only needle-shaped bubbles in the ice. The volumes of ESBs and NSBs both increase linearly with the bubble growth time at all freezing temperatures. These findings help deepen the understanding of trapped air bubbles in ice and provide guidance for improving icing and optimizing deicing strategies.