INVESTIGATION OF KINETICS FLOWS IN A ROTARY-FILM EVAPORATOR

The processing of raw materials in thin layers has a special significance in the technological food processes, because technology frequently involves operations of concentrating liquid products, which can lose the beneficial properties when heated to high temperatures and which can stick when processed for a long time. In this case, the efficiency of using apparatuses is higher; therefore the rotary-film evaporators are widely used also in chemical, pharmaceutical and other industries. The article presents the results of the investigation of kinetic motion of fluid flows in a rotary-film evaporator, and also analyzes the factors affecting the evaporation process in the mobile thin film. It has been determined that to obtain high-quality condensed products depends on the uniform distribution of the solution treated on the working surface of the apparatus. The visual observation of the film forming process has shown that the fluid in the gap between the working surface of the apparatus and the jacket of the rotor blade forms a movable wedge. It enables to use the analogy with the lubrication theory when describing the wedge motion in the sliding bearing. The analytical method for constructing dependences was used to conduct the quantitative analysis of the impact of the design and operational parameters of the apparatus on the uniformity of the film distribution of the solution treated. The expression to identify the blade force on the solution has been obtained by converting the analytical expression of the shear stress between layers. The analysis of the influence of solution viscosity, pressure in the apparatus and the rotor rotational speed on the uniformity of the liquid film formation has been carried out. The graphical method found the direction of the forces from the blades at different operating parameters and determined the direction of flow in the amount of rotary-film evaporator. The recommendations for selecting the design and operating parameters of the apparatus have been offered on the basis of the results obtained.