Vacuum cooling of liquids: mathematical model Original Research Article

Vacuum cooling is very often used when a fast temperature decrease of products is required. Particularly food, pharmaceutical and other industrial areas take advantage of a fast cooling process which reduces high temperature effects and minimizes the time during which, for example, an increased growth of microorganisms can occur. The basic principle of vacuum cooling consists in removing of the latent (evaporating) heat of a solvent (usually water), which implies a fast decrease of the cooled liquid temperature. To keep the evaporation process running, continual reducing of the total pressure in the equipment must be applied. This paper describes a simple mathematical model of the vacuum cooling process which enables to predict a temperature evolution regarding an equipment size, vacuum pump parameters and properties of the cooled liquid. Real thermophysical properties of the cooled liquid are considered in the model along with the assumption that the main resistance against mass transport is situated on the side of liquid phase. Parameter identification of mass and heat transfer coefficients based on literature experimental data together with results of numerical simulation of a real vacuum cooling equipment are described at the end.