Technical Physics最新文献

The paper presents the results of an experimental study of the solubility of tannin in SC-CO₂ on isotherms of 308 and 333 K in the pressure range from 8 to 26 MPa. The range of the Reynolds number is established at which the equilibrium concentration (solubility) of tannin in SC-CO₂ is ensured.

In this paper, the mechanical properties of thin films of filled ethylene-vinyl acetate copolymer and specially synthesized tin oxide nanoparticles are investigated. Tin oxide nanoparticles synthesized in a plasma discharge under the action of ultrasonic cavitation have a size of 50–60 nm, and under ultrasonic exposure, the particle size is 30–40 nm. Using these two types of nanoparticles (before and after ultrasonic exposure), samples of films from composite materials were obtained and studied. The results of studying the fractures of films obtained at the temperature of liquid nitrogen by scanning electron microscopy show that the structure of the material is integral, there are no visible large defects and cavities. Physical and mechanical tests of a film made of a composite material with different contents of tin oxide nanoparticles were carried out. The results of mechanical tests show that ultrasonic treatment of tin oxide nanoparticles before their impregnation into a polymer matrix has a positive effect on the physical and mechanical properties of films made from the studied composite material.

The work is devoted to mathematical modeling of the dynamics of inhomogeneous electrically charged media. The dynamics of gas suspensions (solid particles suspended in a gas) is investigated. The mathematical model has implemented a continual approach to modeling the dynamics of inhomogeneous media; the model takes into account the interphase momentum exchange as well as the interphase heat transfer. The carrier medium is described as a viscous, compressible, heat-conducting gas. The equations of the mathematical model are supplemented with initial and boundary conditions. The influence of the physical density of the dispersed phase material on the intensity of interaction in electrically neutral and electrically charged gas suspensions is investigated. Both surface and mass densities of electric charge are considered.

An analysis of the phase behavior of binary systems is presented, including one of the representatives of aromatic alcohols (phenyl ethanol) and two potential extractants intended for use in the supercritical fluid (SCF) state. The study of the phase state of the thermodynamic systems “CO₂–benzyl alcohol” and “propane–benzyl alcohol” in the near-critical region of the state has been carried out using a high-pressure optical cell. For the first time, data on phase equilibria of the “propane–benzyl alcohol” system have been obtained. The states of different phases are fixed.

Results of modeling the processes in the multisprayer combustion chamber of the gas-turbine engine operating on a gaseous fuel are presented. Two options of the combustion chamber (basic and modernized) are considered. The basic option is analyzed and design shortcomings are revealed. The design is also improved by inserting plugs on the rings of a flue tube, by redistributing openings over the length of the flue tube and by changing the nozzle design. The results of calculations confirm the effectiveness of the measures taken for reducing the concentration of nitrogen oxides in combustion products.

The problems of environmental safety and resource conservation in processing industrial waste at Russian oil and gas facilities are becoming more and more significant, especially in the context of current trends focused on decarbonization and sustainable development. The growth of industrial waste is not compensated by corresponding growth in the volume and quality of processing since only 10% of oil-containing waste is processed, and the rest is buried or incinerated, which has an additional harmful impact on the environment. This paper proposes a new approach to multifactor analysis of resource conservation and environmental safety in the integrated processing of industrial waste from oil and gas facilities to achieve sustainable development goals. The algorithm developed by the authors, the theoretical basis of which is the method of data envelopment analysis (DEA), determines the sequence of solving interrelated problems of multifactor comparison of objects of the waste processing system by heterogeneous quality criteria: resource value, resource potential, resource saving and environmental safety. These issues are formulated on the basis of a super-efficiency model of the DEA method as a mathematical programming problem. The presented and tested approach to the multifactor analysis of resource conservation and environmental safety of the waste treatment system allows (1) to obtain and analyze relative comparative assessments of waste storage facilities and technologies regarding heterogeneous quality criteria and (2) to form local and general decision-making strategies for sustainable development goals. The proposed approach appears promising for multiple prospective applications in the oil-bearing regions of the Russian Federation, where the growth in the formation of industrial waste has severe and irreversible environmental consequences.

The paper provides data based on an analysis of the results of mathematical modeling in COMSOL Multiphysics software, which allow to determine the acoustic efficiency of a noise barrier with cylindrical top device depending on the height of the barrier, the diameter of the device and the position of the cylindrical device relative to the top edge of the barrier. It was determined that a higher barrier increased the length of interference region (the region of local maxima and minima of the top device efficiency) and significantly affects the acoustic efficiency of the top device at octave bands of 250, 500, 1000 and 2000 Hz. The cylindrical device with the installation angle α_inst = 90° was found to be the most efficient for a constant distance of 5 m from the noise source to the barrier in all cases. It is shown that the acoustic efficiency of the top device with different angles remains almost constant when the barrier height is increased from 1 to 2 m. When the barrier height was increased to between 3 and 5 m, the acoustic efficiency of the device increased by about 2 dBA. The acoustic efficiency of the cylindrical device was found to increase by 2 or 3 dBA on average as the top device diameter increased from 0.2 to 0.5 m.

The effect of heat transfer in the wall in the direction of the flow of heat carriers on the effectiveness of heat exchangers is considered for the cases when the wall ends are not thermally insulated from the environment. Use is made of the analytic solution to the problem of parallel-plane flow of heat carriers, which has been considered earlier. The solution depends on the following parameters: ratio of coefficients α of heat transfer from heat carriers; ratio of thermal equivalents β of heat carriers (it is assumed that α = β = 1); number Ntu of heat-transfer units; parameter C_A characterizing the axial heat conduction of the wall; the Biot number determining the relative heat transfer from the wall ends to the environment, and the temperatures of the media contacting the wall ends. The effect of the heat conduction the wall increases with decreasing C_A. The following two cases are considered: (case I) the temperatures of the environment are assumed to be equal to the inlet and outlet temperatures of the hot heat carrier; (case II) these temperatures are equal to the inlet and outlet temperatures of the cold heat carrier. It is shown that for large Biot numbers (Bi > 1), the effectiveness of using of one of heat carriers can be elevated due to the effect of the axial heat conduction of the wall; in this case, the temperature of the other heat carrier during its flow in the heat exchanger varies insignificantly. The boundaries of the beginning of the effect of the axial heat conduction of the wall on the effectiveness of the heat exchanger are determined.

Heat transfer on surfaces with fiber brush coatings has been studied for free-convection liquid boiling. The influence of operating and design parameters on heat transfer coefficients and critical heat fluxes has been revealed using a graphical analysis of experimental data. Criterial equations for estimating heat transfer coefficients and critical heat fluxes under the considered boiling conditions have been derived.