Parameter Sensitivity of the Microdroplet Vacuum Freezing Process
The vacuum freezing process of microdroplets (<100 μm 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 coefficientKis essentially different between microdroplets (<100 μm) 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 coefficientklaffected the cooling stage, whereaskiaffected the freezing stage. Heat capacityClaffected the cooling stage, butCihas virtually no effect on all stages. The actual latent heat of freezingΔHwas also affected. Higher density corresponds to lower cooling rate in the cooling stage.