The work examines the heat exchange characteristics of a condenser in which heat removal of the refrigerant condensation occurs due to natural convection and radiation cooling. The heat exchanger is designed to reduce energy costs for the removal of condensation heat. Unlike traditional air cooling condensers, it uses radiation cooling, a method of heat removal based on its transmission in the form of infrared radiation through the planet’s atmosphere into the surrounding outer space. A method for calculating the thickness of the radiating plate has been developed. To minimize material consumption and cost, the distance between the tubes is reduced to 40 mm, and the thickness of the aluminum radiating plate is reduced to 0.32 mm. The inner diameter of the coolant channels is 1 mm.
For the experimental study of the condenser, an experimental stand working on R134a refrigerant was developed. Theoretical and experimental studies of heat transfer have been carried out. The heat transfer coefficient of the heat exchanger, reduced to the area of the radiating surface, was from 10.3±1.36 to 18.7±2.47 W·m–2·°C–1, when the condensation temperature was 12.8...21.9 °С higher than the temperature of atmospheric air. The operability of the condenser is shown both during the day and at night, in the presence of precipitation in the form of rain and snow, and a high level of cloudiness.
The material capacity and filling of the refrigerant in the condenser are comparable to the characteristics of air-cooled condensers with forced air circulation. At the same time, it does not consume electricity. It can be used in stationary refrigeration systems (in data processing centers, commercial refrigeration equipment, air conditioners) to increase their energy efficiency
The purpose of the work is to study the structural features of the tripod-type parallel manipulator as well as to solve direct and inverse kinematic problems for such a manipulator. The developed algorithms and computer-generated programs for synthesis and analysis of the tripod-type parallel manipulator are useful for designing spatial mechanisms with parallel kinematics with many degrees of freedom, with an arbitrary number of edges and an arbitrary arrangement of segments with different kinematic pairs that can be used in many ways. For example, the foregoing can be used in machine processing of the inner surfaces of the cavities of complex shape, during maintenance and reclamation work in pipeline, during surgical operations in medicine etc.
The subject of the study is the process of active ventilation of wheat grain with variable heat supply. The purpose of the work is a mathematical description of the nature of the flows of matter and energy in the process of active ventilation of wheat grain. Thanks to the selected original design of the exhaust coolant outlet unit, made in the form of a mesh spiral tube, it was possible to optimize the hydrodynamic situation in the layer of dried grain. The developed mathematical model, as a mathematical description, consists of equations of material, thermal balances, equations of hydrodynamics in steady and unsteady states. This mathematical model is the basis for creating a material model of the process and conducting an experiment with subsequent data processing. As a result, it is possible to obtain criteria equations of processes that make it relatively easy to calculate processes under various technological modes.
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