Intensification of heat exchange by an ultrasound source for milk pasteurization.

The goal of this article is to investigate the effect of ultrasonic vibrations on the process of milk pasteurization. Ultrasound can potentially intensify heat transfer and reduce the formation of thermal sediment (soot deposit) on the walls of heat-exchange devices. The paper presents the results of experimental studies demonstrating the growth rate of thermal sediment on the wall of the heat-exchange apparatus and its amount in the volume of milk under the influence of ultrasonic vibrations and without it.

INTENSIFICATION OF HEAT EXCHANGE IN DIABATIC RECTIFICATION COLUMNS

The heat exchange in a diabatic column was investigated during the rectification of an ethanol-water mixture, in which partial condensation of rising vapors on the surface of vertical heat exchange tubes installed vertically along the height of the installation was carried out, as well as the evaporation of intermediate condensate on the surface of horizontal plates. Based on the review of diabatic columns, it is shown that they can reduce the cost of conducting the rectification process. Heat-exchange devices placed on trays of rectification units are considered and ways to intensify heat transfer in them are proposed. It has been established that the most efficient heat removal in heat exchangers of diabatic columns is achieved when using a film flow of a coolant on a heat transfer surface. Heat transfer in a diabatic column is investigated during gravitational flow of surfaces of heat exchange tubes, as well as when organizing an ascending and descending co-current film flow, both in the case of heating and boiling of the coolant. To intensify heat transfer in the coolant film, a helical artificial roughness was installed on the surface of the pipes, made in the form of a wire spiral tightly mounted on the heat transfer surface. The geometric parameters of the helical roughness, such as the distance between the turns of the spiral and the height of the wire, which have the greatest influence on the intensity of heat transfer, have been established. Dependences for determining the value of the heat transfer coefficient are presented and an estimate of the value of the specific heat flux in the diabatic column is given.

Innovative heat pipes and thermosyphons for renewable sources of energy application

In the paper the authors present possibilities of use two-phase heat-conducting devices at cooling technologies for PV and PV/T solar cooling and air-conditioning. Three ways to improve heat conductive properties of heat pipes and thermosyphons with help of nanotechnologies are considered: use of nanofluids, application of nanocoatings on heat loaded surfaces and polymer composites with nanoparticles producing. A mini bubbles generation of the working fluid inside the transparent thermosyphon evaporator with nanocoating under the solar radiation influence was observed. Nanotechnologies allow to intensify heat transfer processes and reduce energy losses in original designs of heat pipes and thermosyphons.