COMPARISON OF METHODS OF HEATING A ROTARY-FILM APPARATUS FOR THE PRODUCTION OF VEGETABLE CONCENTRATES

The object of research is the temperature field of the working surface of the rotor-film apparatus (RFA) when heated by a nichrome spiral with a different coolant layer or using a flexible film resistive radiating type electric heater (FFREHRT). Since the concentration of vegetable purees using RFA is a promising solution, due to a significant reduction in processing time and high quality of the resulting products. Today, most RFAs use electric heating of nichromes with spirals with intermediate coolants, to process a uniform heat flow, which is determined empirically for the thickness of the coolant layer depending on the flow of raw materials, it is processed. Such methods make it possible to obtain qualitative indicators of the uniformity of the temperature field, but the problem is an increase in the metal consumption of the apparatus due to the presence of pumps for the movement of coolants, which generally complicates the operating conditions. Therefore, it is important to improve the RFA heating system using FFREHRT, which is also a thermally insulated surface with a uniform distribution of the temperature field over the entire radiation plane. In the course of the study, the uniformity of the temperature distribution in the RFA model sample is determined for various heating methods (nichrome wire with an intermediate coolant, PFMS-4 organosilicon liquid or FFREHRT). The obtained comparison of heat removal methods made it possible to establish that heating with a nichrome spiral is optimal when the thickness of the coolant layer is 4 mm with a temperature difference of 1.2...2.4 °C . Under conditions of using FFREHRT, a temperature difference of 0.5...0.7 °C. This confirms the prospects of using FFREHRT in the RFA heating system in the conditions of a change in the feed rate of 0.5...1.5•10 3 kg/s. Thanks to the use of FFREHRT for RFA heating, operational conditions will be improved by simplifying the structural properties, reducing resource costs compared to heating with a heating shell with a coolant and the optimal temperature difference on the working surface of the apparatus.


Introduction
One of the main operations in the production of vegetable semi-finished products is the concentration of mashed potatoes according to the technological requirements for the required dry matter content [1,2]. A promising heatexchange equipment in this case is rotor-film apparatuses (RFA), which are characterized by a significant reduction in processing time and high quality of the products obtained [3][4][5]. As well as the possibility of their direct location in lines near the places of collection of raw materials [6]. This will ensure a decrease in transportation costs, as well as preservation of the initial properties of the raw materials, which largely depend on the operating parameters of the temperature and uniformity of heating of the raw materials, necessitating the search for innovative solutions to improve the heating methods of RFA. Today, most RFAs use electric heating of nichromes with spirals with intermediate coolants to ensure uniform heat flow, which is determined empirically for the thickness of the coolant layer depending on the flow rate of the processed raw materials [7]. Such methods make it possible to obtain qualitative indicators of the uniformity of the temperature field, but are characterized by increased metal consumption of the apparatus, the presence of pumps for the movement of coolants, in general, lead to a complication of operating conditions [8]. Therefore, the engineering solution to improve the RFA heating system through the use of a flexible film resistive electric heater of the radiating type (FFREHRT), which is simultaneously a heatinsulated thermal surface with a uniform distribution of the temperature field along the entire radiation plane, is relevant [9].
Thus, the object of research is the temperature field of the RFA working surface when heated by a nichrome spiral with a different layer of coolant or FFREHRT. The aim of research is establishing the optimal temperature distribution in RFA under conditions of comparisons of the indicated methods of heat reduction depending on the consumption of raw materials. TECHNOLOGY AUDIT AND PRODUCTION RESERVES -№ 6/3(50), 2019 ISSN 2664-9969

Methods of research
A study of the uniformity of the temperature distribution in the RFA model sample depending on the heating method is carried out by the location of thermocouples on its working surface ( Fig. 1, a). RFA consists of a heat-insulated casing of apparatus 1, which is heated by FFREHRT or a nichrome spiral with an intermediate coolant (organosilicon liquid PFMS-4 [10]).
The upper part of the RFA has a separation space 3 for the removal of secondary steam. Here the apparatus is a rotary rotor 4 with hinge elements 5. On the upper part of the rotor there is a distributor 6 for film formation of the raw material before concentration, coming through the nozzle 7. The lower part of the RFA is the discharge zone of the finished concentrate with nozzle 8. The temperature of the experimental section is 25 mm in height from the upper edge of the loading nozzle, and its length -10 mm is determined by the chromel-kopel thermocouples located on it 9. So, to study the uniformity proposed three levels of thermocouples, three thermocouples in each (Fig. 1, b).

Research results and discussion
Experimental determination of temperature uniformity on the RFA heating surface under conditions of comparison of heating using a nichrome spiral with a different layer of intermediate coolant (PFMS-4, δ t : 0, 2, 4 mm) and FFREHRT. When using a nichrome spiral with a coolant with a layer thickness of 4 mm, the temperature difference is set in the range of 1.2...2.4 °C. The thickness of the coolant 0 and 2 mm have a more uneven temperature distribution with a change in the flow rate of raw materials within 0.5...1.5·10 3 kg/s (Fig. 2).
Analysis of the curves (Δt) shown in Fig. 2, confirms the optimal level of temperature difference in the range of 0.5...0.7 °C on the working surface of the device under conditions of use in the RFA-FFREHRT heating circuit. The technical characteristics of FFREHRT make it possible to obtain a uniform distribution of the amount of heat in almost any area of the working surface. This will lead to improved operating conditions of RFA by simplifying the structural properties, reducing resource costs compared to heating a heating shell with a coolant.

Introduction
Current nutritional requirements require the consumption of polyunsaturated fatty acids, essential amino acids and minerals in sufficient quantities. But usually modern nutrition does not fully satisfy the need for such important components [1,2].
A particularly acute issue of good nutrition is relatively certain categories of the population, in particular, people who engage in sports activities. Preparation for the competition, daily training, high psychological endurance require special nutrition, which will contribute to high endurance and quick recovery [3][4][5]. In order to meet the needs of the body of a person involved in sports, special