Experimental Modeling of Process of Water Solutions Evaporation in the Vacuum and Microwave Field Conditions

Abstract

A comparative analysis of traditional methods for the food solutions concentration is given. The main problem of classical evaporators is identified, which is associated with the impossibility of obtaining high concentrations of the finished product due to a sharp increase in its viscosity and temperature through the formation of a boundary layer. A scientific and technical hypothesis has been formulated, representing a possible solution to this problem by providing a volume supply of energy directly to the moisture of the product. Thermophysical scheme of evaporation processes by traditional and innovative methods is considered. Their fundamental differences are highlighted and the relevance of the development of an innovative evaporation method is substantiated. The scheme of the innovative evaporator is presented, which allows to obtain the finished product in the solid phase with a final concentration of up to 90 °brix. By the example of apple juice, experiments were conducted to study the effect of pressure of the electromagnetic field on the steam output of the apparatus. Dependencies that indicate a constant evaporation rate throughout the entire process, up to a concentration of 80-85 °brix, were built. The product temperature did not exceed 35-40 °C, which may indicate its high nutritional value. The above data confirm the formulated hypothesis about the possibility of transition in the process of evaporation from the boundary conditions of the 3rd type to the boundary conditions of the 2nd type by the using microwave energy. 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 number of energetic action and the obtained dimensionless complex.