MODELING OF ICE FORMATION ON CYLINDRICAL SURFACE OF CAPACITIVE CRYOCONCENTRATOR

Separating freeze-out (cryoconcentration) is widely used for liquid products concentration including milk and secondary dairy raw materials processing. This method allows us to obtain high quality concentrates. Separating freeze-out of nonfat milk have been investigated. The laboratory capacitive cryoconcentrator allows simultaneous separating freeze-out of nonfat milk in one cylinder and frozen fraction melting in another one. Water fraction melting in one cylinder is carried out due to the heat taken away from the ice formed in the other cylinder. The temperature of heat exchange surface of the container in which separating freeze-out takes place is kept stable ( up to ± 0.2°) in the range of minus 2 to minus 8. The ice on the heat exchange surface of the capacitive cryoconcentrator is formed in the form of a hollow cylinder. Its wall thickness depends on the temperature of the heat exchange surface and separating freeze-out duration. Modeling of technological processes is an important stage in the technological design of food productions. Mathematical modeling makes it possible to lower material and time expenditures during the design of technological processes and to find the most effective technological solutions. Mathematical model for crystallization of nonfat milk water fraction on the cylindrical surface of the capacitive cryoconcentrator has been developed according to the classical equations of heat and mass transfer. Initial data for finding the dependence of the layer thickness of ice frozen out on the cylindrical surface on the process duration are the surface temperature of the cryoconcentrator and cryoscopic temperature of the concentrated product as well as geometrical parameters of the cryoconcentrator. The estimated dependences obtained were compared with experimental data. The compliance of the estimated model of nonfat milk separating freeze-out on the cylindrical surface to the real process of separating freeze-out has been established.