An experimental study of the effect of air quality on frosting on cold flat surface

摘要

The effects of air quality in the freezing process of droplets and the frost crystal growth on cold flat plate are studied experimentally. It is found that the air quality has important influence in the frosting process. The supercooling degree and freezing time change with solution concentration on different solutes. When supercooled droplets are in the instability state, the composition and concentration of solution can affect the nu-cleation and heat transfer, and most of the solute can increase the degree of supercooling and accelerate the freezing process. Solutions with cation of strong electrolyte have higher supercooling degree because the weak cation will hydrolyze. The hydrated ion can accelerate the formation of ice crystal. In addition, the frosting process on cold flat plate under different fine particle (PM2.5) concentrations is also studied in form of frost height and mass variations. The result shows that the greater the PM2.5 concentration is, the thicker the frost layer is and the greater the amount of the frost crystal is. This is because suspended particles in the air that can act as nucleating substrate to promote heterogeneous nucleation and the frost crystals are more easily deposited.