Solar energy is considered a renewable, most environmentally friendly and carbon-free form of energy. Solar collectors are one of the implementations of radiation life support systems. Their development requires a fairly large amount of initial data, such as the parameters of the premises, the required temperature, volume, thermal insulation of walls, floors and ceilings, the design of windows and doors, orientation to the cardinal points, the angles of inclination of the roof slopes, etc. The next group of factors is related to the location object, latitude, altitude above sea level, distance to large bodies of water, wind rose, etc. The third group is related to the weather itself: precipitation, cloudiness, outside air temperature, etc., a significant part of them, such as fog, haze, dew, shadow from each cloud affects the amount of insolation and all this cannot be taken into account in advance. The use of weather archives does not allow us to fully determine the specific thermal performance of solar collectors, since neither the average nor the current insolation is reflected in the archives. Without knowing the amount of real insolation and heat losses on the solar collector, it is impossible to determine the thermal performance of the radiation life support system per day, month, season or year. This paper discusses experimental and computational studies of the radiation life support system carried out in 2018–2022.

The analysis of the main modern technologies for obtaining low temperatures and liquefying hydrocarbons using compressor equipment is presented and the most significant results of research in the field of low-flow compressors based on low-speed, long-stroke piston stages are presented. A method for calculating an ideal vapor-compression refrigeration cycle is presented, adapted to the object under consideration, taking into account the possibility of implementing quasi-isothermal compression. A comparative computational analysis of temperature conditions and thermodynamic efficiency of a two-stage refrigeration cycle and single-stage refrigeration cycles is carried out during adiabatic and quasi-isothermal compression processes in the boiling temperature range 278 K ... 198 K. It is shown that in terms of the discharge temperature and coefficient of performance, a single-stage vaporcompression ammonia refrigeration machine based on a low-speed quasi-isothermal stage is comparable to a similar two-stage machine based on adiabatic stages. This allows, in relation to actual objects — small refrigeration machines and installations, to predict both the energy and technical advantages of using a single-stage scheme based on low-speed, long-stroke piston compressors. In addition, it has been shown that the effective use of such a compressor is also possible in hydrocarbon liquefaction systems, while ensuring their safe temperature conditions in a wide range of atmospheric temperatures.

The current level of performance of piston compressors, characterized by the delivery coefficient, is at the level of 0,7. Advanced designs have higher rates, reaching values of 0,8...0,85. However, the negative effect of dead volume prevents the performance level of, for example, screw compressors from being achieved. Therefore, reducing the influence of dead volume on productivity can be considered the main task in improving modern piston machines.

The presented work proposes a solution to eliminate the influence of the most significant component of the dead volume — linear space. As experimental studies have shown, the use of elastic discs mounted on the piston will virtually eliminate linear dead volume, ensure operational safety and increase the flow rate to 14 %.

The procedure for conditionally dynamic (quasi-dynamic) hydraulic and thermal calculation of recirculation lines of compressor stations has been developed. As an example, the solution to the problem of reconstruction of the linear compressor station of the main gas pipeline is considered. Using the developed methodology, options for upgrading the existing recirculation line in order to increase its throughput are proposed. The gas temperature change in the recirculation line is analyzed due to various factors (heat exchange with soil, throttling) at the starting modes of constant and variable rotations of the compressor rotor. The analysis of the change in the recirculation cycle time and the rate of temperature growth at the compressor inlet per unit time is performed.

The article presents a mathematical model of a mobile compressor station with a heat recovery system based on a refrigeration machine. The study outlines the heat recovery system scheme, based on which the mathematical model is developed. The model includes known thermodynamic relations for the heat load on heat exchangers, power consumed by the compressor, and the coefficient of performance of the refrigeration machine. The presented model allows for determining the efficiency of the system and conducting calculations of the equipment and units comprising it.

This article is devoted to the study of thermal conductivity of nanofluid. A nanofluid is a liquid in which nanometer-sized solid particles are dispersed. These particles are called nanoparticles. Nanofluids have new promising thermophysical properties compared to conventional heat transfer fluids. Thermal conductivity is one of the main thermophysical properties of a liquid. Thermal conductivity is of great importance in processes where heat transfer and fluid flow occur. The article presents well-known theoretical models for determining the thermal conductivity of nanofluid. A brief description of these models is given. Some experimental work on determining the thermal conductivity of various nanofluids is considered. A computational study of the effect of aluminum oxide (Al2O3) and silicon dioxide (SiO2) nanoparticles on the change in thermal conductivity of a nanofluid has been performed. A comparative analysis of known computational models and experimental data is carried out. The accuracy of the calculated models is determined by determining the thermal conductivity of the nanofluid.

In the course of work on the energy perfection of thermal control systems for spacecraft with a twophase circuit, the issue of partial regeneration of thermal energy into electrical energy in a low-speed turbogenerator is considered, part of the design work requires computational modeling during the transport of swirling flows in the axial direction from the external input to the input plane into the impeller, which determines the need for theoretical and experimental elaboration of the problem. The paper considers transformations of equations for changing the amount of fluid motion in boundary conditions of an axial annular channel with fixed cylindrical surfaces. Assuming the symmetry axis of the flows using the integral form of writing the continuity equation, the relations are obtained in the form of two differential equations with expressed derivatives along the channel axis for the total pressure p* and the circumferential velocity constant Cu = UR (const — at the integration step). The equation forms the basis of the algorithm of integration in finite differences supplemented by a system of service equations describing the friction stress, thermodynamic parameters, etc. Test calculations are carried out using real parameters, the results are analyzed.

The article discusses promising penetrators with non-removable transparent and removable opaque windows, created mainly from corundum and ice composite, respectively. Their use will expand the scientific research program due to visualization capabilities for video recording of the movement of the penetrator in the subsurface layers of soil and their optical methods of studying, as well as direct contact with them. The calculation method and the calculated values of damage to these windows from the impact of spherical particles of lunar regolith with diameters of 1,0 and 1,5 mm, colliding with them at speeds of up to 1 km/s in the angular range from 70° to 80°, obtained using numerical modeling or based on an engineering model, are discussed.

This paper discusses properties of various 3D printing materials, namely, plastics, including polyamides, along with composite or engineering plastics with inclusions of carbon fiber and fiberglass. We have selected an optimal sample printing mode and carried out experiments, following which we have determined maximal loads for test composite materials, and linear shrinkage. As the result, we have determined an optimal 3D printing mode for various structures of composite material parts with the purpose to reach the set design–engineering parameters. 

This article raises the topic of modernization of existing technological processes of procurement production in terms of eliminating the expensive and lengthy stage of designing and manufacturing metal molds and the introduction of 3D printing technologies. The article provides information about 3D printing technology based on the extrusion method. Information is provided on the main stages of designing the tooling for the «Insert» part, taking into account the features and limitations associated with printing on 3D printers. As part of the study, the roughness and shrinkage of test samples are analyzed, which are made on a 3D printer from various composite materials.

During the experiment, carried out in two stages, a thin-film coating of molybdenum is obtained on substrates made of steel grade HVG. The first stage included preliminary ion implantation of molybdenum. The second stage is the production of a thin-film molybdenum coating by balanced magnetron sputtering. During the study using scanning electron microscopy, microphotographs are obtained that visually confirmed the uniformity and homogeneity of the thin-film coating. The values of average surface roughness Sa is obtained by probe microscopy suggest that it decreases after applying a thin-film coating. Using the energy dispersive analysis method, the mass concentration of molybdenum on the surface of the modified tool steel was determined, which is 92,4 %. Experimental modes of modification of KhVG steel with a thin-film coating have been obtained, which have a significant effect on the average roughness and microhardness of its surface. It has been shown that the experimental modes used in the work make it possible to obtain a strengthening of the surface of HVG steel after applying a thin-film coating of molybdenum, with preliminary ion implantation several times. The adhesion force between the thin-film coating and the HVG steel substrate is determined. High adhesion values obtained using the method proposed by Gerald Frankel from Ohio State University indicate good quality of the applied coating. All of the above indicates the prospects of using the above-mentioned methodology in the mechanical engineering industry.