Parameter Sensitivity of the Microdroplet Vacuum Freezing Process

The vacuum freezing process of microdroplets (<100 μ 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 is essentially different between microdroplets (<100 μ 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 affected the cooling stage, whereas affected the freezing stage. Heat capacity affected the cooling stage, but has virtually no effect on all stages. The actual latent heat of freezing was also affected. Higher density corresponds to lower cooling rate in the cooling stage.