DETERMINATION OF THE HEAT TRANSFER COEFFICIENT OF A ROTARY EVAPORATOR WITH HEATING FILM-FORMING ELEMENT

Abstract

In the article, a model of a rotary-film evaporator with a film-forming element, which has a heated reflective surface, was investigated. Such a solution was proposed to stabilize the hydraulic movement of the cut off wave flow due to the reflective surface of a certain geometric shape for the forced direction of the cut raw material to the heating surface. Autonomous heating of the reflecting surface additionally provides a temperature effect in the conditions of movement of raw material particles after cutting. As a result of the analysis of the experimental and theoretical parameters of heat transfer, the criterion equation for the heat transfer coefficient of the evaporator with the proposed film-forming element, which has a reflective heated surface for calculating the heat transfer coefficient from the working surface to the raw material, is substantiated. The resulting equation takes into account the influence of the vertical component of the motion of the raw material film, the centrifugal movement during the rotation of the film-forming element, the mixing of the boiling film of the raw material with steam bubbles, the geometric characteristics of the film-forming blade on the hydrodynamic flow of the raw material. Calculation of a rotary-film evaporator using a criterion equation and a useful heat exchange surface of 0,75 m2 was obtained. The specific metal content in a rotary-film evaporator with a film-forming element having a reflective surface is 57 kg/m2 compared to the vacuum evaporator traditionally used in canning industries 410 kg/m2, which is 7,1 times less. Also, the duration of the temperature effect on the raw material is reduced: a rotary-film evaporator - 200 s and 3600 s in a traditional apparatus. The obtained data will be useful for designing rotary-film apparatuses of various geometrical parameters using hinged blades with a reflective plate.