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In this work, the thermal conductivity of refrigerants systems from three different hydrofluoroolefins including R1234yf, R1234ze (E), and R1233zd(E) were studied using artificial neural network. A total of 4395 data points of liquid and vapor thermal conductivity at several temperatures (241.92 to 344.46) K and pressures (0.068 to 21.73) MPa were used to train and test the model. Five neurons were used in the input layer, fifteen neurons at hidden layer and one was used in the output layer. Bayesian Regulation back propagation algorithm, logarithmic sigmoid transfer function, and linear transfer function were used at the hidden and output layer, respectively. Temperature, pressure, applied heating power; acentric factor and dipole moment were considered as input variables of the networks. The optimal parameters were obtained through the weights searching method. The average absolute relative deviations and correlation coefficient were 1.48 and 0.9998, respectively. This study shows therefore that the artificial neural network model represents an excellent alternative to estimate the thermal conductivity of different refrigerant systems with a good accuracy.

A general analysis of heterogeneous sources of waste heat at thermal power plants, taking into account the advanced world and domestic experience in creating high-power steam compression and absorption thermal transformers, has shown the possibility of significantly reducing heat losses by integrating absorption heat pumps and refrigerating machines of various designs and capacities into the thermal circuits of existing and projected thermal power plants. It is proposed to carry out a comprehensive optimization of the plants by creating intra-plant trigeneration systems. Taking into account the specific operating conditions of steam turbine condensers, cheaper multicomponent LiCl salt-based aqueous solutions, which are not inferior in efficiency to imported LiBr solutions with anticorrosive additives, are offered for the use as working bodies.

The paper presents the results of thermodynamic calculations and experimental studies on plasma processing of spent fuels and lubricants, which showed the prospects of using the plasma-chemical technology for processing liquid industrial wastes with the production of fuel gas and inert mineral material. The comparison of experimental and calculation results showed an acceptable agreement.

Results of an experimental study of the influence of argon addition on microwave plasma chemical vapor deposition of diamond from a hydrogen-methane mixture are reported. A specific feature of this method is the use of a high-velocity jet for transporting gases activated in a microwave plasma in the discharge chamber to the substrate located in the deposition chamber. Optical emission spectroscopy is used for systematic investigations of the microwave discharge plasma in the discharge chamber. Diamond coating samples obtained on the molybdenum substrate are studied by methods of scanning electron microscopy and Raman scattering spectrography.

The present numerical study is aimed at revealing the influence of the distance between the nozzle exit and the resonator edge on the gas-dynamic characteristics of the acoustic-convective flow in the flow path of a bichannel system. The aim of the work is the development of a computational technology for describing the physical processes in the flow path of multichannel systems that generate high-intensity acoustic fields. Five configurations of the bichannel system were considered, where the gap was 0.85, 1.10, 1.35, 1.60, and 1.85 of the resonator diameter. As a result of the study, a complete picture of the gas-dynamic flow formed in the flow path of the bichannel system was obtained, including the resonating cavity and the region in between the nozzle and the resonator. With the help of numerical simulation, the formation of a flow with high-frequency, low-amplitude oscillations at a small gap between the nozzle exit and the resonator edge, which was observed in experiments, has been demonstrated. Pure-tone oscillations with maximum intensity occur when the resonator is placed in the region of the beginning of the second barrel, this observation being in good agreement with the data by other authors. Subsequent increase in the distance between the nozzle and the resonator leads to the emergence of subharmonics and multiple harmonics. Verification of gained numerical results with known experimental data is carried out.

Modeling of processes with phase transition in confined spaces needs high-accuracy simulations with account for non-equilibrium. In the present paper, we use the direct simulation Monte Carlo method for describing evaporation into a vapor-filled half-space with a subsonic monoatomic gas flow. Two types of boundary conditions for open half-space are considered: the interaction approach with consecutive calculating of temperature and pressure, and the approach with a fixed velocity. We compared these approaches for obtaining the accurate solution of the problem. The fixed-velocity approach provides a higher accuracy for the flow with a low Mach number. The calculated results are compared with a known solution of a model kinetic equation.

The present work deals with the design optimization of different vehicle configurations for planetary entry. Choosing the aerothermodynamic characteristics of heat flux and drag as the objective function we have analyzed and simulated the effects of atmospheric resistance on planetary entry vehicles in the rarefied atmosphere. We have utilized the SPARTA (Stochastic PArallel Rarefied-gas Time-accurate Analyzer) DSMC simulator for our simulation. The optimization is carried out with the help of MATLAB optimization module. We have simulated the descent of the present work demonstrates two of the planetary atmospheric conditions, the first one is Earth, and the later one is Mars. The vehicle geometry is then optimized according to the planetary atmospheric conditions. This work ultimately provides insight into how the effects of geometrical parameters play a pivotal role in the aerothermal loads of planetary entry vehicles.

The problem of laminar mixed convection is considered in a flat vertical channel with lifting and lowering flow and liquid heating, i.e., for cases of coincidence of the directions of free and forced convection, as well as their opposite directions. The solution of the system of equations of motion, continuity and energy is performed by the finite difference method. Data on the profiles of the longitudinal velocity, temperature, and Nusselt numbers at the lifting and lowering flows have been obtained. An explanation is given for the peculiarities of these values under the influence of buoyancy force. All components of the hydraulic resistance coefficient for lifting and lowering flow have been analyzed. The influence of the Prandtl number and the velocity profile at the channel input on the hydrodynamic and thermal characteristics of the flow is considered.

Within the framework of the linear subsonic theory, the problem of influence of flow boundaries on the flow around airfoil according to the measured distribution of pressures on the airfoil and on the test-section walls is solved. For the test case (testing a BGK1 airfoil in the IAR1.5m wind tunnel), we compared the corrections to the oncoming-flow Mach number and to the airfoil angle of attack that were obtained using our method and in works by other authors. For a OSPB-77 airfoil model tested in the T-128 wind tunnel for two values of wall permeability, ƒ = 0 and 3 %, correction of distributed data and integral loads was applied in the range of Mach numbers from 0.2 to 0.78. The application of corrections has made it possible to bring the results for ƒ = 0 and ƒ = 3% in closer agreement up to the angles of attack at which flow separation occurs on the airfoil.

The structure of a slug gas-liquid flow and interfacial mass transfer during the flow of ethanol-N₂ and ethanol-CO₂ mixtures in a horizontal rectangular microchannel have been experimentally studied. The experiments were carried out in a straight microchannel with a cross-section of 380×190 µm. To determine a change in the volume of a gas slug along the microchannel length, the method of high-speed visualization with digital processing was applied. In a wide range of gas flow rates, the repetition rate and the volume of gas slugs and their velocity were measured, and he volumetric coefficient of mass transfer from liquid was determined for the ethanol-CO₂ mixture. A physically substantiated model of interfacial mass transfer for a slug flow in a channel of rectangular cross-section, which takes into account the circulation flow in a liquid bridge, is proposed.