Parameter sensitivity of the microdroplet vacuum freezing process

Abstract

The vacuum freezing process of microdroplets (<100 m in diameter) is studied by dynamic mesh method. The mass transfer coefficient was studied using the results of related papers that considered droplet diameters exceeding 1 mm. The diameter, initial temperature, and vacuum chamber pressure effects are also discussed. To estimate parameter sensitivity, the effects of material density, specific heat, and thermal conductivity in 20% scope, as well as latent evaporation/sublimation in 5%, were simulated. The results show that the mass transfer coefficient K is essentially different between microdroplets (<100 m) and macrodroplet (>1 mm). Pressure and droplet diameter have an effect on cooling and freezing stages, but initial temperature only affects the cooling stage. The thermal conductivity coefficient k l affected the cooling stage, whereas k i affected the freezing stage. Heat capacity C l affected the cooling stage, but C i has virtually no effect on all stages. The actual latent heat of freezing Δ H was also affected. Higher density corresponds to lower cooling rate in the cooling stage.