Growth and distribution characteristics of trapped air bubbles in ice slices

Abstract

Icing is a complex phase change process that is widespread in nature and industry and may have a number of negative effects. During the freezing of water into ice, air bubbles are often trapped in ice and affect the physical properties of the ice. To control the icing process, it is necessary to study these air bubbles in ice. Here, an experimental setup is built to study the growth and distribution characteristics of trapped air bubbles. The results show that the critical freezing rates for the transitions from the egg-shaped bubble region to the egg-/needle-shaped bubble region and from the egg-/needle-shaped bubble region to needle-shaped region are 22.45 ± 3.24 and 12.64 ± 1.65 μm/s, respectively. A mathematical model that can predict bubble growth is obtained by coupling the gas diffusion equation, Henry's law, and the Young–Laplace equation. The model shows that both the maximum width of the bubble and the distance between adjacent bubbles mainly depend on the freezing rate and are proportional to the inverse of the second power of the freezing rate, meaning that the maximum width and the distance gradually increase as the freezing rate decreases. These results contribute to a better understanding of icing mechanisms and inform the optimization of anti-icing and deicing methods.