EXPERIMENTAL MODELING OF THE VAPORIZATION OF LIQUID SOLUTIONS UNDER VACUUM AND MICROWAVE FIELD CONDITIONS

The paper provides a comparative analysis of traditional methods of concentrating food solutions. The author identifies the main problem of classical evaporators, which is associated with the impossibility of obtaining high concentrations of the finished product due to a sharp increase in its viscosity and temperature caused by the formation of a boundary layer. He puts forward a scientific and technical hypothesis offering a possible solution to this problem by providing a considerable supply of energy directly to the product moisture. The paper outlines thermophysical and physical schemes of evaporation processes based on traditional and innovative methods. Their fundamental differences are highlighted and the relevance of the development of an innovative evaporation method is proved. The author presents a scheme of an innovative evaporator, which allows to obtain the finished product in the solid phase with a final concentration of up to 90°brix. The author reports on the experiments conducted with apple juice to study the effect of pressure and power of the electromagnetic field on the steam output of the evaporator. As a result, he established relationships that indicate a constant evaporation rate throughout the entire process, up to a concentration of 80-85°brix. The product temperature did not exceed 35…40°C, which may indicate its high nutritional value. The above data confirm the formulated hypothesis about a possibility of transition from the boundary conditions of the 3rd type to the boundary conditions of the 2nd type by using microwave energy in the process of evaporation. On the basis of the obtained results, a model in the criterial form was obtained, which makes it possible to accurately calculate the performance of a microwave vacuum evaporator in certain ranges of the energy deposition number and the obtained dimensionless group.