Table of contents

XXXIV Siberian Thermophysical Seminar (STS-34)

The Siberian Thermophysical Seminar is traditionally held at Kutateladze Institute of Thermophysics of Siberian Branch of Russian Academy of Sciences in Novosibirsk since 1960. In 2018, the Seminar has been dedicated to 85th anniversary of Academician Alexey K. Rebrov, who has been working at the Institute of Thermophysics from its founding. His work is inseparably linked with development of thermophysics and rarefied gas dynamics in Russia.

The present Conference covers the following topics:

• turbulent flows, heat and mass transfer in single-phase environments, intensification of heat transfer;

• heat and mass transfer in chemical transformations, including combustion;

• heat and mass transfer in phase transformations;

• multiphase flows and wave processes in gas-liquid systems;

• thermophysical problems of energetics, energy efficiency and energy saving;

• nonequilibrium processes in rarefied gas and plasma;

• thermophysics of micro- and nanosystems, gas-phase synthesis of nanostructures;

• thermophysical properties of substances and radiant heat exchange.

The number of participants reached 203 researchers from 11 cities in Russia with a good share of young members. There were 12 keynote and 20 invited lectures as well as 162 oral and 35 poster presentations. The keynote lectures have been presented by Profs. A. K. Rebrov, S. V. Alexeenko, V. M. Fomin, M. R. Predtechensky, I. V. Egorov, A. M. Krivtsov, V. Ya. Rudyak, S. A. Novopashin, N. M. Bulgakova, E. A. Kolubaev, G. V. Kuznetsov, S. F. Chekmarev. The proceedings in this volume contain 158 papers grouped by sections where they were presented.

The Scientific Committee appreciates the enormous work of the editorial board and reviewers in the preparation of this volume. We would like to express our sincere thanks to all authors for their research contributions, and also to organizers of the conference for their valuable spadework. Special thanks to the Russian Foundation for Basic Research for the financial support (grant 18-08-20064).

STS-34 Co-Chairmen

D. M. Markovich

A. N. Pavlenko

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Heat transfer in the channel behind a back-facing step with organized perturbation in the form of a rib was experimentally investigated. The separated flow developed in the positive pressure gradient at Re = 12,000. The influence of location and height of a single rib on pressure distribution and intensification of heat transfer behind the back-facing step was studied. It is shown that installation of a single rib increases heat transfer behind the back-facing step in the positive pressure gradient. The positive pressure gradient leads to a decrease in heat transfer behind a step both with a presence of additional disturbing elements and without them.

The evolution of a buoyancy induced jet in a high-viscosity liquid with Pr = 2700 over a suddenly switched-on linear heat source is numerically investigated. The dependence of the velocity, temperature, and local heat fluxes on time has been investigated at a layer height of 50 mm and the Grashof number Gr = 172. Numerical simulation is performed using the finite element method. The complete system of equations of nonstationary thermogravitational convection for a two-dimensional flow is solved. The dependence of the spatial forms of flow and velocity fields on the power of the heat source is studied experimentally. Digital video shooting and computer processing of video films are used to determine the velocity fields. The results obtained can potentially be useful in the creation of adequate models of thermal plumes.

The paper presents the results of visual study of the structure of a round minijet flowing into the atmosphere exposed to an acoustic field. The studies were performed with the laminar jet flow. According to the photo and video recording of the flow pattern we revealed characteristic features of the jet structure in the acoustic field. Characteristic vortex structures and zones with intense turbulent mixing were detected in the flow. We revealed the process of vortex structures formation in a laminar jet under the effect of the acoustic field, vibrational and rotational regimes of jet flows at the outlet of the pipe 1.35 mm in diameter. The present study is the continuation of the research on a minijet structure in an acoustic field [10].

A sonic nozzle with a toroidal inlet region, cylindrical throat and a stepped diffuser with cylindrical sections were considered. An analytical method was proposed for estimating the required pressure drop for the nozzle operating in a critical flow regime. The results of analytical estimation of the pressure buildup in the nozzle steps were compared with the ones of numerical simulation. It is shown that replacing the conical divergent section of ISO 9300 standard nozzle with easy-to-manufacture stepped divergent section leads to a twofold increase in the required pressure drop for the nozzle operating in the critical flow regime, which in many cases is acceptable.

The process of heat transfer due to natural convection in narrow vertical water-filled pipes is considered. Experimental and simulation data are given. The mechanism of natural convection development is analysed.

The experimental data are presented for the velocity in the slits of guiding apparatus for the classic open vortex chamber as well as for the Ranque tube. In both cases at the linear rise of the mass flow rate with increasing of overpressure level, the essential slowdown was observed for the growth of the slit velocity. At that the ratio of the slit to the critical sound velocities (the velocity coefficient) either tends to an asymptotic limit that is less than unity, or becomes equal to unity at a certain overpressure level and no more changes.

We performed direct numerical simulations (DNS) of the turbulent annular jet flow for the Reynolds number Re = 8900 with three different values of the inner-to-outer diameter ratio (a = d / D = 0.3, 0.5, 0.7). The time-averaged velocity fields and fluctuations were analyzed. The low aspect ratio results in the shortest recirculation zone while for high a value the stagnation point features high level of turbulent kinetic energy. This is the evidence of the accompanying low-frequency oscillations of the recirculation zone.

Regimes of mixed convection of melts with Prandtl numbers Pr = 10.78 and 16 were simulated experimentally and numerically in an application to hydrodynamic model of Czochralski with a fixed crucible case. In mixed nonstationary regimes the forced flow is induced by a uniformly rotating crystal under a given mode of thermal gravitational-capillary convection. The experiments and calculations were carried out with 96% ethanol (Pr = 16) and water (Pr = 10.78) as modelling fluids. When Pr = 10.78, abnormally high value of surface tension leads to an increase of the influence of the thermocapillary effect and the appearance of heat exchange features. Nonstationary flow regimes are determined within the range of Reynolds number 82 ≤ Re ≤ 103 at Pr = 16.

The evolution of the local characteristics of natural convective boundary layers along the longitudinal coordinate is studied experimentally. The spatial forms of secondary flows in boundary layers on the walls of the plane and annular vertical liquid layer heated to different temperatures and in the core of the layers are studied. Hot walls are transparent, which allows video recording in two planes. In the regions of the laminar, transition, and turbulent boundary layer, local fields of velocity and temperature and local heat fluxes are measured.

The article considers heat transfer in a flow of helium-xenon mixture in straight and twisted tubes with triangle cross sections. The main attention is paid to the heat transfer at large Reynolds numbers for tubes with small effective diameter. Such flows are often found in compact heat exchangers, assemblies of heat-generating elements, and energy-separating devices. CFD simulation data serve to analyze the influence of the cross-section shape and the twist step of the tube on hydraulic resistance and heat transfer. Various methods of generalization of heat exchange data are analyzed, taking into account the effect of gas compressibility on the flow acceleration in the tube and dissipative effects on the equilibrium wall temperature.

A theoretical asymptotic model for large amplitude stationary axisymmetric inertial waves in an axially symmetric swirling flow of an ideal fluid in a circular infinite tube with variable cross-section is described. Calculations are presented for the special, but important case when the upstream flow is uniform and always supercritical. It is found that the breakdown of inertial waves in divergent tubes is extremely sensitive to the variations of the cross-section. The breakdown bubble is generally asymmetric and it may turn into the diverging tail, especially in a convergent part of the tube. Possible relevance of the calculated structures to the experimentally observed types of the breakdown is discussed.

Gas-dynamic perfection and intensity of heat exchange of intake systems determine the efficiency of the piston engine. The results of numerical simulation and experimental study of the heat transfer of gas streams in the intake system of engines having different configurations are presented in the article. Methods of modeling, experimental setup, geometric configuration of pipelines and measuring base are described in the paper. The investigations were carried out under steady-state air flow in the system. The results of mathematical modeling were verified using experimental studies. It is established that the use of profiled sections in the intake system leads to a decrease in the heat transfer rate up to 20 % at low air flow rates (up to 40 m/s) and an increase in the heat transfer rate up to 9 % at high speeds.

The paper reports on numerical simulation of a weakly accelerated turbulent boundary layer over the permeable wall. Helium-xenon mixture was injected into the xenon main flow after the laminar-turbulent transition. The finite difference method was applied to solve a system of boundary layer equations with variable gas properties supplemented by the k-ω-γ turbulence model. It has been shown that the light gas injection into the accelerated turbulent flow leads to arising of velocity maximum within the boundary layer and its partial laminarization.

The paper presents the results of experimental investigation of transverse streamlining of a circular cylinder by turbulent water flow within a range of Reynolds numbers 1.75 × 10⁵ − 2.9 × 10⁵. In the experiment, two circular smooth stainless steel and fluoropolymer (PTFE) cylinders, which have the same size and roughness, but differ in the degree of hydrophobicity, were used. Using the PIV method, the data on the averaged velocity field in the vicinity of the cylinders surface have been obtained. For these fields, the vortex structures in the near wake have been investigated, and their spatial and kinematic parameters have been compared. It is shown that starting from Reynolds number 2.1 × 10^5, the reverse flow length and the distance between the vortices behind the steel cylinders decreases by 2.2 and 2.3 times, respectively, in contrast to the fluoropolymer cylinder, where this distance decreases by 1.1 and 1.2 times.

The paper presents the results of an experimental study of the hydrodynamics of jets flowing from long tubes at low Reynolds numbers. The main attention in the research is given to the mechanism of interaction between pipe and jet instability, which results in a vortical motion in several spatial regions. In the experiments we used Hilbert-visualization, high-speed visualization, and measurements with a hot-wire anemometer. The subsonic gas jet flows into the air space from a long tube with a diameter of 2, 3.2, and 5 mm within the Reynolds number range of 200-6700. Air and Freon-22 were used as the working gases. The critical pipe Reynolds numbers are characterized by the mechanism of a two-stage instability caused by the formation of turbulent spots (puff) inside the tube and generation of vortex structures in the jet mixing layer. These organized structures (puff) exert a strong influence on the free jet flow destroying the laminar flow part. The obtained data make it possible to consider in detail the evolution of turbulent spots along the distance downstream, while the spots are generated in a cylindrical tube due to the laminar-turbulent transition.

The results of experimental studies of hydrodynamics and heat transfer in a swirl air flow (Pr = 0.7) and a helium-xenon mixture (Pr = 0.2) in heated circular channels with original screw inserts in a wide range of Reynolds numbers are presented. The efficiency analysis of heated channels with a swirl of the flow is compared with the efficiency analysis of the channels without swirling the flow using the energy necessary for pumping the gas through the heated channel.

In the current study, the authors present a brief overview of the main factors that affect the processes of heat and mass transfer in the urban environment, and also consider the possibilities of using the ANSYS Fluent software to simulate urban climate problems. A test configuration, which corresponds to the open experimental data, was chosen for the numerical simulation. The boundary and initial conditions for the configuration were set in such a way as to reproduce the conditions of the weakly-unstable thermal stratification of the air flow. Satisfactory agreement of the experimental and simulation data on velocity and temperature profiles was obtained.

Heat transfer in pulsating air flow behind the rib in the channel entrance has been studied experimentally. An experimental facility and the technique to estimate heat transfer with simultaneous wall heating and wall temperature measurement by the same copper tracks have been developed. Distributions of heat transfer coefficient over the heated channel wall in steady and pulsating regimes of flow have been obtained. Enhancement of heat transfer in pulsating flow up to 25% in comparison with a steady flow has been revealed. The studies have been carried out within the frequency range of 0-15 Hz and the relative amplitudes of forced velocity pulsations of 0.8.

The article presents the results of the study of vortex formation and integral heat exchange in the air flow around the building model system. The experimental setup, measurement methods, results and their analysis are described. The analysis of the phenomena specific for the given model configuration at different mutual model arrangements is presented.

Experimental data on the averaged and pulsating characteristics of the flow in divergent channels within a wide range of unsteadiness parameters have been obtained. To measure the dynamics of instantaneous velocity vector fields and Reynolds stresses, the optical method of Smoke Image Velocimetry (SIV) has been employed. The effect of forced flow pulsations on these characteristics has been described depending on the correlation between the maximum pressure gradient related to the variable cross-sectional area of the channel and flow unsteadiness.

A mathematical model of the process of nonstationary heat transfer between active thermo-emission thermal protection system (ATETPS) and convective gas flow is given. The effect of electron's evaporation (emission) from the surface of the emitter on lowering its temperature is studied.

Heat transfer in pulsating air flow in a rib-roughened channel has been studied experimentally. Heat transfer was estimated using the technique of simultaneous wall heating and wall temperature measurement by the same copper tracks. Distributions of heat transfer coefficient over the channel wall in steady and pulsating regimes of flow have been obtained. 30% augmentation of heat transfer compared with the steady flow values has been revealed in pulsating flow. The frequency range of (0–100) Hz and the relative amplitude of forced velocity pulsations of 0.3 have been studied.

The two-dimensional melting process of paraffin enhanced by Al₂O₃-nanoparticles inside a copper radiator with various frequency of finning is studied numerically. The governing equations have been formulated in dimensionless stream function, vorticity and temperature. The obtained system of partial differential equations has been solved using the finite difference method. The influence of the frequency of the fins location on the melting process of paraffin with different nanoparticles volume fraction has been studied.

Experimental results on the flow structure and heat transfer of the pulsating cross-flow past the in-line and staggered tube bundles have been obtained. The effect of forced flow pulsations on the statistical characteristics of flow in the gap between the inner-row tubes was analyzed for different pitch values. Average heat transfer in steady and pulsating flow past the bundle has been measured. Correlation between heat transfer and the variation of flow pattern in the gap between the tubes has been determined. The opportunity to enhance heat transfer in the tube bundle by forced freestream pulsations has been shown.

Experimental data on production, dissipation, turbulent and molecular diffusion of turbulent energy have been obtained in the boundary layer of flow with forced freestream velocity fluctuations. The evolution of these terms over the pulsation phase is presented for streamwise and wall-normal velocity components. The presented results have been obtained on the basis of the dynamics of vector fields measured using a new optical SIV method with a spatial resolution comparable to the Kolmogorov scale.

Pyroelectric energy harvesting is an important option for powering autonomous electronic devices. For the technology to be efficient high-frequency thermal oscillations are needed. Here we suggest a method of creation of thermal oscillations in a pyroelectric plate, based on Karman instability. Vortices, shedding alternatively from the two sides of a heated body, accumulate heat in their cores and transfer it to a pyroelectric plate. The effect is demonstrated by means of numerical simulations. A number of geometries were considered, to optimize the parameters of operation and achieve maximal thermal oscillations in the plate. A prototypical device for waste heat harvesting is presented. It is able of achieving harvested power of 1 W/g for a thin (200 nm) plate of ferroelectric (BaTiO3).

The radiation-convective heat transfer from the crystals in methods of pulling from melts such as Czochralski, Stepanov and floating zone is investigated numerically in the conjugate statement of the problem. The calculations are performed in the ranges of Grashof numbers from 1000 to 25000, with the gas Prandtl number equal to 0.68. Calculations of convective heat transfer are carried out by finite element method, and radiation fluxes are calculated by the zonal method. The relative role of thermal conductivity, convective heat transfer and radiation heat transfer is investigated.

We report on Large Eddy Simulation of a stably stratified atmospheric boundary layer with a simplified river flow at the bottom boundary. The shear generated by the friction of water surface leads to creation of the air flow in a thin layer above water surface. Stratification prevents vertical motion due to negative buoyancy effects, and the flow expands in horizontal direction. This leads to accumulation of kinetic energy of the flow in a narrow layer near the surface (about 10 meters), where the air velocity may reach about a half of the velocity of the river surface. In case of strong inversion magnitude (20°C/km) the effect of formation of large-scale vortices was found for such configuration. These vortices significantly intensify heat and mass transfer in horizontal direction. The formation of these vortices is attributed to the process of inverse spectral transfer of turbulent energy, possible because of a quasi-two-dimensional structure of the flow.

The paper is devoted to a numerical study of the characteristics of a cycloidal rotor depending on its construction features. It is established that the 2D simulation does not adequately resolve the investigated problem. This is connected with the complex three-dimensional structure of the flow formed by rotor. The 3D calculations allow detecting sucking in airflows into the end faces of rotor. This requires studying the effect of the end faces construction. Two rotor geometry options with open and closed end faces are considered. The significant dependence of formed flow structure behind the rotor, rotor thrust, and energy characteristics depending on the design of its end faces is established.

This experimental study explores an intriguing phenomenon occurring in two-fluid swirling flows. In a sealed vertical cylindrical container, the flow is driven by the rotating lid while other walls are stationary. The lid rotation generates the meridional circulation of an adjacent fluid. The fluid goes from the cylinder axis to the periphery near the lid and back near the interface. This centrifugal circulation tends to propel the counter-circulation of the lower fluid. In contrast, the rotation tends to propel the co-circulation of the lower fluid. Thus, the two competing factors — (1) swirl and (2) meridional velocities at the interface — tend to push the lower fluid in opposite directions. As the rotation intensifies, factor (1) dominates over factor (2) and the new flow cell emerges near the interface in the lower fluid. The emergence of the new flow cell was predicted by numerical simulations. The current work provides the first experimental evidence of the new-cell development in the lower fluid.

This paper deals with an experimental study of the vortex structure of interacting coaxial swirling flows in an isothermal model of adaptive burner used for combustion of low-grade fuel. The working section consists of two consecutively connected tangential swirlers. Depending on the method of liquid flow supply to the second stage, both co-swirl and counter-swirl of two flows occur in the working section. In experiments, the effect of the flow swirl method on the resulting flow structure was studied with varying flow rates. Time-averaged distributions of axial and tangential velocity components along the entire region of the resulting flow were obtained using laser-Doppler anemometry. Experimental results have shown that counter-swirl is more preferable for the use in a two-stage burner because it promotes faster mixing of the burner jets of the first and second stages and more uniform filling of the internal volume of device.

The problem of determining the equilibrium states of reacting thermodynamic system that is the molecules of substances consisting of only oxygen and carbon atoms has been numerically solved basing on given external parameters (pressure and temperature). Here it has been assumed that the shift of system chemical equilibrium resulting from the chemical reaction can imply the presence of condensed carbon as suspended ultradispersed graphite particles among the gaseous products of reaction. In computations, the values of pressure, temperature and the relation of concentration of oxygen and carbon atoms have been varied. The conditions, under which carbon condensate appears in the reaction products and homogeneous thermodynamic system becomes heterogeneous one, have been determined.

The paper represents the thermal imaging measurements of external flame during the combustion of diesel fuel and spent transmission oil in a perspective steam-atomizing burner. The experiments are conducted in a wide range of operating parameters (rate and temperature of steam and fuel consumption). A thermal imaging camera (FLIR, JADE J530SB) is used for measurements. The results show that the effective emissivity coefficient depends on the flow rate of supplied steam. The effect of the burner parameters on the temperature in the external flame of the burner is revealed. The data obtained can be used for numerical modeling of combustion.

The paper provides a numerical investigation on focal ignition and flame propagation in an aluminum-air suspension. The aim of the research was to determine the apparent flame propagation velocity in the aluminum-air suspension depending on the size and mass concentration of the aluminum particles. Numerical simulation showed that the smaller the particle radius the stronger the apparent burning velocity of the suspension depends on the initial mass concentration of the aluminum powder. The obtained results qualitatively correspond to the experimental data described in the scientific papers.

A pilot 10 kW burner of novel design using a concept of hydrocarbon fuel combustion enhancement by axial injection of superheated water steam jet is considered. Numerical simulation of turbulent reacting flow and heat transfer, including the radiative heat transfer, soot and NOx formation processes, during combustion of vaporized diesel fuel in this burner has been performed in 2D axisymmetric formulation. As a combustion model, the conserved scalar approach with constrained-equilibrium chemistry model has been used with account for 3 inlet streams and 32 species. The field distributions of velocity, temperature, concentrations of gas species and soot have been obtained from numerical predictions. The numerical results allow to conclude that the effect of combustion intensification, observed in the burner outer flame, arises from the fuel gasification process enhanced by the influence of steam jet.

By the example of diesel fuel, the combustion of liquid hydrocarbon fuel in a burner device with a forced controlled steam supply is experimentally studied. Spraying of liquid fuel is provided as a result of its interaction with a high-speed jet of superheated steam, without fuel contact with the atomizer. This method of dispersion has significant technological advantages in the use of substandard liquid fuels. These are associated with the prevention of clogging of the atomizer and fuel supply channels, which improves the performance and reliability of the burner device. The composition of combustion products and the specific heat power are studied in a wide range of changes of the operating parameters of the burner device (steam flow rate and fuel consumption). The regimes under which high fuel combustion completeness is ensured at low content of harmful emissions in gaseous reaction products have been found.

The present paper describes a numerical code for simulation of detonation flows on hybrid computational clusters (CPU/GPU). The code can solve 1D, 2D and 3D unsteady Euler equations for multispecies chemically reacting flows using high-order shock-capturing TVD schemes and a finite-rate chemistry solver. The implementation is based on the OpenMP, MPI and CUDA technologies allowing for both flexibility and computational efficiency of the code. The program is verified on the analytical Zeldovich-von Neumann-Doering solution for the 1D detonation wave in H₂/O₂ mixture. Some examples of 2D computations are also given.

Present work studies the ignition of a brown coal by a hot metal particle. The experiments establish the limits of the gas-phase ignition and ignition delay times in conditions whee the metal particle situated on the surface of dispersed coal layer. The coal particle size was different in different series of experiments, and it was ranged from 0.1 to 1 mm; the shapes of the metal particles were sphere, disk, and cube; their initial temperature varied between 1000 and 1400 K. Three modes of gas-phase ignition of coal were established with the ignition zone of volatiles located in the vicinity of the hot particle. The practical application of obtained results is the development of fire prevention guidelines for tightening fire safety management at productions dealing with coal mining, transportation, storage, processing, and combustion.

In this paper the effect of fire front on the surface of wood samples (pine, aspen and larch) was considered to estimate the effect of different wood-fire retardants. Infrared thermography was used as a diagnostic method. Modern methods of IR-diagnostics and the use of thermal imagers eliminate the need for a large number of thermocouples which perturb the investigated medium during measurements. At the same time, a much better resolution in space and time can be obtained using infrared diagnostics. The surface temperature distribution was obtained for the test wood samples after exposure to a fire front that was modeled using pine needles. The ignition probability was estimated for the chosen experimental parameters for each kind of wood. In the infrared region the sample surface characteristics were recorded using a thermal imager JADE J530SB with a 2.5 − 2.7 micron optical filter that allowed measuring a temperature within the range of 500 − 850 K. In order to record a temperature within the range of 293 − 550 K, the recording was conducted without a filter. The fire hazard characteristics of wood after fire retardant treatment showed a significant reduction in the surface temperature and the resistance to fire for the chosen parameters of the experiment compared to the same untreated samples.

The probe sampling of gases is extensively used in studies of high-temperature oxidation processes. This technique allows one to obtain directly information on the chemical composition of the reaction volume, however, inevitably introduces thermal and gas-dynamic perturbations into the system. In order to further numerically simulate the sampling process, the temperature profiles of the quartz probe surface in the CH₄/O₂/Ar flames were measured in a pressure range of 1-5 atm. The measurements were carried out by thermographic method using an IR camera, which was calibrated by direct thermocouple measurements taking into account flame shielding. The data obtained will be used as boundary conditions for computer simulation of the sampling processes, which will significantly improve the accuracy of the sampling probe methods.

We have numerically investigated the problem of kerosene droplets evaporation with dilute concentrations of aluminum nanoparticles at elevated temperatures. The aim of the research was to develop a mathematical model describing the evaporation process and obtain numerical simulation data which is in good agreement with an experimental data. The dependences of kerosene droplet evaporation time on its initial diameter and ambient temperature are presented in this paper.

The paper presents verification of the mathematical model and the results of a numerical research of the influence of operating conditions on the formation of nitrogen oxides during the combustion of coal-water fuel in a promising low-capacity boiler. For the numerical simulation of turbulent flow of an incompressible liquid, we used the approach of Reynolds-averaged Navier-Stokes equations (RANS) taking into account the interfacial interactions. To solve the equation of thermal radiation transfer, the P1 approximation of spherical harmonics method was employed. The optical properties of gases were described based on the sum of gray gases model. To describe the motion of coal particles we used the method of Lagrange multipliers. The combustion process of coal-water fuel is considered in terms of the following consecutive steps: evaporation of the water part of the droplet, evaporation of moisture from the fuel, devolatilization and the combustion of the volatile components, and the combustion of the coke residue. Comparative analysis has shown that the selection of the operating conditions of the boiler has a significant influence on the oxygen concentration in combustion chamber and the temperature of the flue gases. This leads to significant differences in the formation of nitrogen oxides during the combustion of coal-water fuel.

This paper describes the application of Recurrent Neural Networks (RNN) for effectively detecting anomalies in time series data obtained from experimental study of the combustion and gasification of mechanically activated coal fuel in a thermal furnace. We train Recurrent Neural Networks (RNN) with Long Short-Term Memory (LSTM) units to learn the normal time series patterns and predict anomaly values. The resulting prediction errors between real and expected values are analyzed to give anomaly scores. To investigate the most suitable configuration of RNN and evaluate the effectiveness of the anomaly detection model, we used three datasets of real-world data that contain several types of anomalies. The developed RNN algorithm detected 9 out the 9 collective anomalies in the hold-out sample with one false positive anomaly event.

This paper is devoted to the study of convection inside a droplet and its effect on heat transfer. A drop of water and a water-salt solution of the LiBr salt was located on a horizontal cylindrical surface of copper. The surface temperature was 53 °C. The novelty of the work is that the influence of free convection in gas and liquid is investigated experimentally. The analysis of experimental data has shown that in the initial period of water drop evaporation, the predominant role in the heat exchange is played by the thermal Marangoni convection.

Setting the optimal pattern of initial irrigation makes it possible to use the maximal packing height without considerable deterioration of mixture separation efficiency caused by formation of large-scale maldistribution of local mixture flows within the packing. Periodic packing irrigation also allows destruction of large-scale structures of local flow maldistribution within the structured packing. This paper presents data obtained in experiments on Sulzer 500X structured packing with the diameter of 0.6 m and height of 2.2 m at periodic packing irrigation. The working liquid was R114/R21 mixture. The packing was irrigated by a liquid distributor with possibility of independent control of any of 123 drip points. The experiments were carried out under the conditions of total reflux (L/V = 1) and L/V = 1.65.

The mathematical model which allows calculating the wave surface profile as well as velocity and temperature fields has been presented. The numerical simulation of wave formation and heat transfer in falling films of liquid nitrogen has been performed. Different activation functions of input perturbations have been examined. The dependences of boiling expectation time and total local evaporation time on heat flux density for different inlet Reynolds numbers have been calculated. The regime map which describes the different mechanisms of film decay was obtained by summing up the simulation results. The results of numerical simulation are in satisfactory agreement with the experimental data.

In this work, the calculation techniques for determining the heat transfer coefficient for boiling non-azeotropic mixtures in tubes are described. In particular, the dependencies proposed by the authors of Shin et al. (1997) and Mezentseva et al. (2014). These dependencies were used to calculate and compare the experimental data on the heat transfer coefficients for the boiling of a non-azeotropic mixture R32/R134a (30/70%) in copper smooth tube with a diameter of 6.34 mm. The results showed that the dependence of Mezentseva et al. (2014) is in good agreement with the experimental data with an accuracy of ± 15%. In addition, this dependence considers the corresponding heat exchange regime and requires less thermodynamic properties of the mixture in calculations.

A new model for the convective drying of a kaolin spherical sample is presented. The model is based on the self-consistent solution of the heat and the moisture transfer equations with the effective thermal conductivity and water diffusion coefficients for wet porous clay-like medium. The radial distributions of the temperature and the moisture content were calculated for different boundary conditions for heat and moisture fluxes on the surface of the kaolin sample. To test the model, the drying kinetics of the kaolin sample heated up to 60°C and 100°C were calculated. The results show a good agreement with the experimental and numerical data of the other authors. In the process of the sample cooling, the effect of the overcooling to the temperatures lower than the ambient temperature was found.

The first experiments on the vacuum drying of spherical clay sample are presented and the theoretical model of the process is considered. The model is based on the solution of the heat and the moisture transfer equations with the effective thermal conductivity and water diffusion coefficients for wet porous clay-like medium. The time and radial dependence of the temperature and the moisture were calculated for different initial conditions. The results obtained for the time dependence of the moisture content are in good agreement with the experimental results obtained in the initial period, when all the moisture in the sample did not freeze to form an ice crust.

A mathematical model of the heterogeneous nucleation of a solid phase in a melt modified by exogenous refractory nanoparticles is developed. Analytical expressions are obtained for the free energy of formation and the rate of heterogeneous nucleation of the solid phase, taking into account the influence of dimensional and capillary effects. The study is of interest for constructing a mathematical model of heterogeneous crystallization that describes the processes of structure formation in metals and alloys modified by refractory nanoparticles.

The processes of water and heptadecane crystallization are investigated numerically and experimentally by a method of the horizontal unidirectional solidification. Water is the simulator of melts with inverse dependence of density on temperature. Influence of boundary conditions on the upper surface of melt layers in regimes of non-stationary buoyancy-thermocapillary induced convection on spatial forms of a flow, temperature fields and solid-melt interface shape is investigated. Cases with rigid top boundary and with free boundary of melt layer are studied taking into account the thermocapillary effect.

This paper presents the mathematical model to simulate the swirling turbulent gas-droplet flow in a sudden pipe expansion. The set of axisymmetrical steady-state RANS equations for the two-phase flow is used. The dispersed phase is modeled by the Eulerian approach. The flow swirl causes an increase in the intensity of heat transfer (more than 1.5 times in comparison with the non-swirling mist flow at other identical inlet conditions). Evaporation of the droplets leads to a significant increase in the heat transfer intensity in the swirling two-phase flow (more than 2.5 times in comparison with the single-phase flow). It is shown that ethanol droplets evaporate much faster than water droplets due to the lower heat of phase transition. The heat transfer enhancement by using ethanol droplets is higher than the corresponding value for water droplets (up to 20%).

The results of an experimental study of the dynamics of rewetting and heat transfer on a copper plate with a structured capillary-porous coating, obtained by directional plasma spraying at film flow of liquid nitrogen are presented. The experiments were carried out at different orientations of the coating relative to the flow of the liquid. A comparison with the experimental data obtained on a smooth heater is made. It is shown that the presence of a coating has a significant effect on the character of the temperature curves and reduces the total cooling time of the plate during rewetting by more than three times as compared to the uncoated plate, but it does not significantly affect the heat transfer under conditions of stationary heat release. Data of high-speed video recording of processes are presented.

The analysis of the heat transfer investigation results has been carried out at boiling and evaporation in thin horizontal layers of liquid on smooth and structured surfaces. Intensive evaporation of thermal plumes at reduced pressure is considered to be the basic mechanism of heat transfer. The thermal plumes could make a significant contribution in heat transfer under conditions of bubble boiling on micro-structured and ribbed surfaces in the areas where vapour bubbles don't emerge.

In this paper the processes of boric acid mass transfer in a WWER-TOI nuclear reactor core in case of the accidents with main circulation pipeline rupture and loss of all AC power supply are considered. The heat removal from the WWER-TOI reactor in case of an emergency process is determined by the use of the passive heat removal and passive core cooling systems. Passive core cooling system of WWER-TOI consists of three stages of hydro accumulators. These systems provide reactor cooling by feed of boric acid solution with concentration of 16 g H₃BO₃/kg H₂O. In view of length of accident process, the boiling of the coolant with high content of boron and considering low concentration of boric acid in the steam leaving the core, conditions may arise for the possible accumulation and subsequent crystallization of boric acid in the reactor that can lead to a deterioration of the process of core heat removal. To assess the chance of accumulation and subsequent crystallization of H₃BO₃ in the core of the WWER reactor, a hand calculation analysis of the change of concentration of boric acid in the reactor in case of emergency mode was carried out. In accordance with the calculation results, if a boric acid concentration in hydro accumulators of passive core cooling systems is 16 g / kg H₂O, than a large excess of the final boric acid concentration in the core is observed in accidents after approximately 43 hours of an emergency process. The options of reducing the concentration of H₃BO₃ to 8, 4, 2 and 1 g/kg H₂O are considered in the calculation process. The obtained results allow us to conclude that a decrease in the concentration of boric acid in the system of hydro accumulators of the third stage would allow to avoid the crystallization of boric acid in the core in the event of an accident.

The paper presents the results of experimental studies of the solubility of boric acid in steam, in a concentration range of 16-245 g H₃BO₃/kg H₂O at atmospheric pressure. An overview of available literature data on the solubility of boric acid in steam, depending on the initial concentration in the water solution is presented. It has been established that the available in literature results do not cover the entire range of parameters (temperature, acid concentration) which typical for a possible emergency situation at NPPs with WWER. The experimental facility and the research procedure are described. The data obtained as a result of the experiments can be used to calculate the accident processes in the WWER reactor facility during the operation of the passive safety systems such as the passive core flooding system, the passive heat removal system from the steam generator and the system of the hydraulic accumulators of the third stage.

The influence of different surfactants on the pool boiling of water and water-based nanofluid was experimentally investigated. The concentrations of xanthan gum and polyacrylamide, which were used as surfactants, were varied from 10 mg/l to 200 mg/l. The concentration of silicon dioxide nanoparticles of 25 nm diameter was equal to 0.1 vol. %. The dependences of the value of the critical heat flux on the concentrations of the surfactants were obtained as a result of the experiments. It was shown, that both xanthan gum and polyacrylamide increase the critical heat flux. The increase in critical heat flux value for water with polyacrylamide relative to the clear water was 61%, and for water with xanthan gum was 32%. The increase in critical heat flux values for nanofluids with polyacrylamide and with xanthan gum relative to the nanofluids without surfactants were 36% and 13%, respectively, and relative to clear water were 263% and 200%, respectively.

The variants of two- and three-dimensional lattice Boltzmann methods (LBM) are described for computer simulations of fluids with liquid-vapor phase transitions and heat transfer. Several improvements of LBM are described (correct implementation of the body force term, "pseudoforces" for the method of "passive scalar" for internal energy and implementation of a latent heat of evaporation). The formation of rivulets in a flow along an inclined flat surface, the fall of a droplet onto a rigid nonwettable plane and the process of spinodal decomposition of initially uniform fluid are modelled.

Gradient heat flux measurement is used in study of heat transfer during condensation of water steam at inner and outer surfaces of the pipe. Experimental setups allow producing experiments with minimal distortion of condensate film flow. Experiments were carried out for different directions of steam and cooling water and for different angles of pipe inclination relative to the vertical. Heat transfer coefficients and their change along the length and perimeter of the pipe were measured. The obtained data allow studying formation of the condensate film and parameters of film motion. The results of these experiments correspond to classical ideas.

This study presents an experimental investigation of heat transfer under condensation inside horizontal multi-microchannel system. R134a refrigerant was used. The copper heat exchanger contains 21 rectangular microchannels with 335 × 930 μm cross-section. Experiments were performed at two mass fluxes 481 to 830 kg/m²s, and vapor qualities ranged from 0.8 to 0.05. Obtained data set on heat transfer and pressure drop was compared with calculation by theoretical models.

The dynamic of explosive vaporization of the water on the multilayer thin-film resistor with the size of 100 × 110 μm has been investigated. An original optical method based on measuring of laser intensity reflected from resistor surface was used. The characteristics of the initial stage of the explosive vaporization were obtained. The dependence of the boiling temperature on the temperature growth rate and the dependence of boiling time on the effective heat flux were defined. The lifetime of the main vapour bubble and the satellite bubble were estimated.

The action of capillary forces during flow condensation of refrigerant R134a in rectangular microchannel is considered numerically using the annular flow model. It was shown that significant accumulation of the liquid occurs near the channel corners and causes the heat transfer enhancement. The heat transfer related to the condensation is taken into account assuming the interface temperature is at saturation. The numerical method is validated against experiments and well predicts the flow patterns inside the microchannel and average heat transfer coefficients.

The aim of the research is to present numerical one-dimensional solution for the temperature distribution in spherical capillary porous body, where the melting and freezing processes are taken into account. The solution includes the non-linear temperature distribution for every moment of heating and cooling at given surface temperature, equal to the temperature of the ambient medium.

This paper presents investigation results on separation of a binary mixture in distillation columns of semi-cylindrical cross-section with structured packing. The effect of vapor and liquid flow rates, packing height on separation efficiency, pressure drop, distribution of local liquid flow rates, temperature, and mixture composition as under the structured packing so in different positions inside the column was studied experimentally. An increase in the ratio of the molar flow rates of the liquid and vapor phases L/V results in a decrease in the height equivalent to the theoretical plate HETP. Increasing of the height of the structured packing leads to deterioration in the efficiency of the mixture separation. To analyze the effect of the shape of the column cross-section on the separation efficiency, the similar experiments were carried out in a round column. The main regularities in the influence of the structured packing height, ratio of liquid and vapor flow rates, and other operating parameters obtained for the round column are also valid for the column with a semi-cylindrical cross-section.

Results of experimental and theoretical research of dynamics of boiling of highly subcooled ethanol in the ring channel under the conditions of pulsing heating of the interior wall are presented. In experiments with the vertical channel, pulsations of a vapor film on a heater wall, accompanied by pressure oscillations with growing amplitude (the self-oscillatory mode), were observed. The mathematical model, which describes the non stationary process of boiling of ethanol in the channel, is presented. Model takes into account pulsations of a vapor film, evaporation of overheated liquid on a heater wall and vapor condensation owing to a flow of highly subcooled liquid. In numerical calculations the conditions of development of self-oscillations owing to evaporation of the liquid getting on a hot wall in the course of pulsations of a vapor film are revealed. Results of calculations well agree with experimental data.

Thermocapillary deformations of horizontal self-rewetting layer of liquid (solution of 1-butanol of 5% concentration in water) when heated from a localized hot spot were studied experimentally. Measurements of the liquid layer deformations were performed using the confocal techniques with three-dimensional positioning system having high-speed linear actuator. Effect of equalizing the profile of the liquid surface over the heating area has been observed before the layer breakdown. The potential interest of the proposed studies induces by the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

The heat and mass transfer in the process of desorption on a free falling liquid film of the LiBr-water solution is analyzed analytically. The dependences of the Nusselt number on the surface on the longitudinal coordinate downstream of the film were found, and the thickness of the film, which changed due to desorption, was determined.The problem was investigated for different values of Froude and Peclet numbers, for different values of initial film thickness.

The dynamics of the geometric parameters of droplets of a water-ethanol solution lying on a Teflon plate was investigated using high-speed microphotography. It was found that the evaporation of water droplets occurred with a constant contact line, and the evaporation of droplets of a water-ethanol solution was accompanied by its movement. At the initial stage of evaporation, the higher the concentration of ethanol in the drop was, the greater was the change in the contact spot diameter, corresponding to the change in the diameter of the spot of ethanol. Using the method of infrared thermography, three stages of temperature change of evaporating droplets were found. The first stage corresponds to the initial sharp decrease in temperature. The second stage is a process at a constant temperature. And finally, the third stage is the stage of its smooth growth to the ambient air temperature. A similar pattern with some features was observed for droplets with different concentrations of ethanol. At the initial stage of evaporation, the droplet temperature changed like the temperature of ethanol droplet, and then its behavior was similar to the temperature change of water droplets. The higher the ethanol concentration in the droplet was, the larger the change in temperature was, similar to the change in the temperature of the ethanol droplet.

The theoretical and numerical study of the periodic regimes of free flowing liquid film is carried out. As a result of the theoretical analysis, a simple three-harmonic model was obtained. The obtained model allowed demonstrating the basic mechanisms of the periodic flow regime. Calculations on the full model, the Nepomnyashchy equation and three harmonic models are performed. The results of the numerical solutions of the Nepomnyashchy equation and new model qualitatively consistent with the results of the solution of the full model are presented.

Today, there is a revolutionary development of microchannel systems. In such systems, it is extremely important to determine the two-phase flow regime, depending on the gas and liquid flow rates. The two-phase flow in the microchannel is affected by many factors, such as the parameters of the initial section, the geometry and dimensions of the channel, the properties of the channel surfaces and liquid. In the present study, we have investigated a two-phase flow in a microchannel with a height of 50 μm and a width of 20 mm. It is shown that, with an increase in the size of the liquid nozzle, the film regimes are replaced by pulsating ones in the investigated range of gas and liquid flow rates. The characteristic frequencies of pulsations, their duration and delays are studied, depending on the superficial velocities of the gas and liquid. It is shown that the duration of the pulsation is mainly influenced by the gas flow rate, and the delay between them – by the liquid flow rate.

A study of velocity profiles in a flow of a multicomponent flow of a guar polymer-based gel in a flat channel was performed. The method of planar shadow image velocimetry was used. It has been demonstrated that a flattening of the velocity profiles in the central part of the flow and an increase in the velocity gradient in the near-wall zone is observed for the cases if such components as fibers and proppant are included in the flow and their concentrations are increased.

The paper presents the results of the experimental study of a downward bubbly flow in a vertical pipe with an inner diameter of 20 mm. The water-glycerol solution was used as the test liquid. The experiments were carried out for different values of Reynolds numbers from 500 to 1500. Measurements of the local flow characteristics (void fraction, liquid velocity, shear stress) were performed using an electrochemical method. The experiments showed a strong effect of the gas phase on the flow structure, expressed in an increase in wall shear stress and a flattening of the velocity profile in the central part of the tube. A significant deviation from a single-phase flow occurs even at low gas-liquid flow ratios.

This work aims at creating a reserve for increasing the efficiency of nuclear power plants. One of the main ways to intensify heat transfer in fuel assemblies is to increase the permissible mass concentration of the vapour phase. It is known that the introduction of a gas phase into a fluid flow leads to a modification of the flow structure and can significantly change the key thermal and hydraulic flow parameters, for example, the heat transfer coefficient. In this paper, we present the results of an experimental study of an ascending bubble flow in a vertical rods bundle 3X3. The working liquid was distilled water. The experiment was carried out at Reynolds numbers from 4000 to 11000 and gas flow rate ratios from 3 to 10%. As a result of the experiment, the heat transfer coefficients from the central rod heated by the electric current to the flow have been determined. It is shown that gas bubbles have the greatest effect on heat exchange at low Reynolds numbers and at a maximum distance from the spacer grid.

Characteristics of the film flow were determined experimentally using simultaneous measurements of the thickness and temperature fields on the surface of the falling heated liquid film (LIF and IR scanner). Three different types of instability were registered on the surface of the heated liquid film: 3D hydrodynamic and two thermocapillary A and B instabilities. The development of thermocapillary structures of type A was considered in the residual layer behind the wave front. These structures caused a disturbance in the following wave front, leading to an increase in the amplitude of the waves. It was found that the amplitude of hydrodynamic waves in the upper part of the heater could be increased. The development of thermocapillary structures of type A at high heat flux initiated increasing of the rivulets deflection amplitudes.

The numerical results of the flow structure in a vertical bubbly polydispersed downward flow in a pipe are presented. The mathematical model is based on the Eulerian approach, which considered the back effects of bubbles on the mean characteristics and turbulence of the carrier fluid phase. The set of axisymmetrical RANS equations is used for modeling two-phase bubbly flows. Turbulence of the carrier fluid phase is predicted using the Reynolds stress transport model. The interfacial transfer of mass, momentum, and energy requires averaging over the computational control volume. The effect of break-up and coalescence of bubbles is taken into account. The effect of variation in the gas volumetric flow rate ratio, inlet mean fluid temperature, and its velocity on the flow structure and heat transfer in the two-phase flow is analyzed. The addition of air bubbles results in a significant increase in the heat transfer rate (up to three times). This effect augments by increasing the gas volumetric flow rate ratio.

The results of an experimental study of the ascent of a compact cluster of monodispersed air bubbles in a viscous liquid are presented. To form a compact cluster of monodisperse air bubbles with given values of diameter and volume concentration, a special experimental setup has been developed. It is shown that the ascent velocity of a cluster of monodispersed air bubbles depends on their number, diameter, distance between bubbles and exceeds the ascent velocity of a single bubble. An empirical dependence for the drag coefficient of the cluster of air bubbles rising in glycerin has been obtained.

In this paper, the effect of nanoparticles addition to the drilling mud on the flow characteristics in an annular channel with a different ratio of diameters and eccentricity was studied, as well as the dependence of the pressure drop, velocity profiles, forces and torque on the concentration and size of silicon oxide nanoparticles at different ratio of pipe diameters and eccentricity.

Results of experimental study of free fluid surface in a fixed long tank (pressure tank) in conditions of mass transfer through the tank are presented. The research has been conducted on an experimental setup that included a model pressure tank to improve the State Primary Standard of volume flow rate GET 64–74 and a simplified system of fluid motion. The effect of free surface wave amplitude in the tank on stability of flow rate maintenance through the metering line of the Standard has been estimated.

In this paper we present results of model experiments on interaction of near-wall liquid film with co-current gas flow inside supersonic nozzle under operating conditions of the International Space Station orientation thrusters. Wave pattern characteristics of films are studied with the help of coaxial capacity-type probes and data on the film local parameters – its thickness and velocity are obtained. It is shown that under the experimental conditions the co-current gas flow exerts strong dynamic impact on near-wall liquid film, leading to intensive wave formation and detachment of droplets by co-current gas flow. It is demonstrated that Weber number can be accepted as the main similarity criterion defining the nature of near-wall liquid film interaction with co-current gas flow under conditions considered.

The results of the experimental determination of dispersity and spatial distribution of droplets in the spray torch of the centrifugal sprayer are presented. The laser complex for spray diagnostic equipped with devices for laser diagnostics of aerosol systems is described. The parametric analysis is carried out, according to its results, the criterion relations for the maximum diameter of the particles in the spray torch of the centrifugal sprayer are presented.

In this paper, an axisymmetric problem of gas outflow from a pipe end to an area of high density (two-phase mixture) is considered. Simulation of the two-phase coolant outflow without phase transition is carried out using a two-velocity model, solved by the LCPFCT software package [1]. Cross-verification is performed with the results of calculation obtained by the OpenFoam software [2] using the VOF method for the approximation of the single-velocity model of a two-phase compressible medium. Using various numerical programs and various physical models of a two-phase medium gives a more complete understanding of the occurring processes.

The paper considers the large-scale characteristics of counter-current gas-liquid flow in the column filled with Mellapak 500Y structured packing. The effect of ascending gas flow on the development of capillary-gravitational instability is determined using flow pattern observations, local liquid flow rate characterization and pressure drop measurements. The correlation for prediction of the critical gas flow factor corresponded to flow flooding is proposed and verified.

The processes of heat and mass transfer in systems with liquid-gas interface are of interest to a wide range of problems. Destruction dynamics of thin horizontal layers of silicone oils were investigated using confocal sensor on a 3D-positioning system. The numerical solution of the problem was obtained in the lubrication approximation theory for two-dimensional axisymmetric thermocapillary flow. The model takes into account the surface tension, viscosity, gravity and heat transfer in the substrate. The numerical algorithm for the joint solution of the energy equation and the evolution equation for the liquid layer thickness has been developed. The establishment method was used to obtain the stationary solutions. Experimental measurements and numerical calculations were made for silicone oils of different viscosities, heating power and initial thickness. The significant effect of the surface tension coefficient and its temperature coefficient on thermocapillary deformation was detected. It was experimentally established that the deformation value depends on a heat flux value. A liquid bump is formed at the boundary of the heating region that is also observed in numerically calculated profiles.

One of the promising ways of removing large heat fluxes from the surface of heat-stressed elements of electronic devices is the use of evaporating thin layer of liquid film, moving under the action of the gas flow in a flat channel. In this work, a prototype of evaporative cooling system for high heat flux removal with forced circulation of liquid and gas coolants, capable to remove heat flux of up to 1 kW/cm² and higher is presented. The peculiarity of the test section used in the present work is that the width of the channel is equal to the width of the heating element (1 cm). It was found that the configuration of the test section allows to get higher values of the heat flux compared with the case when the channel width is higher than the width of the heater, since in the latter case some portion of liquid is deviating from the heater due to the thermocapillary forces.

The paper is devoted to numerical simulation of the regimes of pulse outflow of various gases (air and argon) into a vertical pipe, filled with a liquid of different density (water and Rose alloy), implemented in the OpenFoam package. This problem has a wide range of technical applications, ranging from the simulation of emergency modes of liquid-metal nuclear reactor operation to the depressurization of underwater gas pipelines, the operation of ship equipment systems, etc. The satisfactory agreement of the results of numerical simulation with experimental data has been obtained.

The current trend towards miniaturization of the devices in various fields of technology has led to the creation of a wide range of heat exchangers with a size from units to hundreds of microns. The analysis of the processes of non-equlibrium phase change in microsystems was performed for high rate of heat and mass fluxes. A new approach for the prediction of the flow boiling and condensing heat transfer in microchannels accounting the suppression of nucleate boiling, two-phase forced convection and non-equilibrium evaporation of a thin liquid film is proposed and verified using experimental data. Numerical study of the explosive boiling in a metastable liquid was performed based on the mathematical model of nucleation that account for thermal non-equilibrium bubble growth model.

The two-phase gas-liquid flow regimes in the horizontal rectangular microchannel using the high-speed video camera and dual-laser scanning were studied. Experiments were carried out in the microchannel with cross section 217x370 μm for the water-nitrogen mixture. The T-shaped mixer was used for gas-liquid flow formation. The influence of T-shaped entrance on the length of a gas and liquid bridges in the microchannel was established. The total pressure drop was measured in the microchannel taking into account the distribution of the gas and liquid bridges.

The effect of polydispersity of bubbles on formation of the spatial structure of the wave field, consisting of a sound forerunner, resonant solitons and trace, is investigated. It is shown that in a polydisperse medium the general structure of the wave field is the same as in the medium with identical bubbles, but the energy and spectral characteristics of all wave field components vary substantially.

The effect of small gas phase additions on heat transfer in downward bubbly flow was shown. Data on the size of bubbles detaching from the edges of an array of capillaries in a liquid flow are given. The influence of the disperse phase dimensions on the heat transfer is discussed. The preliminary data of PIV investigation of liquid velocity distribution is also presented. It is shown that change in the size of the dispersed phase can lead to both intensification and deterioration of heat transfer as compared with a single-phase flow at constant flow rates of liquid and gas at the channel inlet. The mechanism of heat transfer intensification was described early. The cause of the heat transfer deterioration is turbulence suppression in the near-wall region.

The paper considers the filtration of ethylene glycol with SiO₂ nanoparticles through the porous sample formed by microsphere packed bed. The experiments were performed for nanoparticles size of 7 nm, microspheres size of 150 μm, and particles volume concentration varying from 0.005 to 0.02. The data on local permeability reduction were obtained for various pressure gradients, and the peculiarities of nanoparticles retention were discussed. It was shown that nanoparticles could be transported through the porous sample, and the retention mechanism could be reversible adsorption on the pore wall. The reversible absorption mechanism of the nanoparticles retention was confirmed by the equilibrium permeability reduction determined by the magnitude of the pressure gradient.

The influence of flow rate pulsations on the rivulet flow regime has been investigated. The experiments were carried out on the underside of a smooth polyethylene plate. The investigation has shown that the influence of flow rate pulsations on the stream patterns is determined by flow peculiarities in the steady-state regime. Disturbances arising from pulsations of liquid flow rate can affect the stream liquid pattern of the rivulet. Such disturbance can cause the development of latent instability at individual points situated along the length of rivulet. The greatest effect on the stream structure is observed for the flow rate pulsation at liquid discharge with the ambiguity of rivulet regime. If the flow rate pulsations affect periodically the meandering rivulet, then it is possible to reduce the degree of meandering and convert the stream into the straight rivulet. In the regime of unstable meandering, it is impossible to identify correctly the effects caused by the flow rate pulsations at the initial area of the rivulet because of great self-acting pulsations of flow rate appearing in different sections along the rivulet.

Using the method of shadow photography, the disperse composition and the structure of the gas-drop flow when used crankcase oil is sprayed with a high-speed jet of heated air were investigated. In a wide range of regime parameters, the droplet size distributions were obtained. The gas temperature range and the distance from the nozzle at which the preferred droplet size in the flow is up to 20 μm were determined for the specified values of air pressure and fuel consumption.

The work is aimed at studying large-scale helical vortex structures emerging in a high turbulent intensively swirling flow in detail. The paper presents numerical simulation of vortex structures by various methods of turbulence. It is shown that the LES method most accurately describes flows in a chamber with a swirling flow. As a result of studies, a strong influence of the geometric parameters of the chamber on the shape of the vortex structures is shown. Steady-state vortex structures are formed in a chamber with a diaphragmatic outlet, while the vortices perform small-scale oscillations around their own axis, called the precession of a vortex core.

The paper proposes a criterion for choosing low-boiling working medium type and the main parameters of the heat recovery unit using the heat of the gas-turbine drive exhaust gases with a capacity of 1 MW for the gas compressor station's own needs and the methodology for determining it at the initial design stage. The data of thermal design and capital costs calculations for the creation of an installation for five types of working mediums are given, as well as the choice of n-pentane as best-satisfying all the requirements.

The experimental results on evaporation of the suspended droplets of distilled water with the addition of 0.1% silicon dioxide with an average particle diameter of 10 nm in a stationary ambient and in an air flow of 0.1 m/s at a temperature of 25 °C to 26°C and 50°C are presented. A comparison is made with the evaporation droplet parameters of the base liquid. Experimental data show that during evaporation the change in the surface temperature of the nanofluid droplets is qualitatively similar to the dynamics of the surface temperature of the mixture droplets, consisting of two pure components with different degrees of volatility.

In this paper, we investigate the effect of mechanically activating grinding of coals of various degrees of metamorphism by two different methods - determination of the flash time in a vertical tubular furnace and thermogravimetric analysis. In the experiments, the coals that had been processed on a vibrating centrifugal mill and a disintegrator were compared. The experiments showed a decrease in the ignition temperature of mechanically activated coals, as well as the effect of mechanical activation on the further process of thermal-oxidative degradation.

The thermal characteristics of a M-cycle counter flow type plate heat exchanger (PHE), intended for use as a cooler, has been investigated numerically as an indirect evaporative cooler. For a fixed heat exchanger length (L = 50d) and the space between plates (d = 6 mm), the investigation included a numerical simulation for the PHE and the study of its performance with the variation in the number of the wetted zone (n) from 1 to 16 for inlet Reynolds number Re = 200. The computational results indicate that the heat exchanger performs better with the number of the wetted zone, high inlet air temperature and low relative humidity. Results show that the cooler consumes less water and it is an environmentally friendly cooler for dry areas.

The paper deals with the investigation of the hydrogen combustion in mixtures of H₂/O₂/H₂O (0.70/0.35/1.64 mol L⁻¹), H₂/O₂/N₂ (0.72/0.34/1.61 mol L⁻¹), and H₂/O₂/N₂/H₂O (0.72/0.34/1.64/0.03 mol L⁻¹) under uniform heating at a rate of 1 K min⁻¹ in a tubular reactor. Based on the comparison of the time-dependent variations of the reaction mixture temperature and the temperature of the reactor wall, the self-ignition temperature is determined as well as the effect of diluent on the nature of heat release was revealed. The contributions of homogeneous and heterogeneous combustion of hydrogen and their effect on heat release in the reaction mixture are discussed. The possibility of hydrogen oxidation enhancement in the H₂O medium, associated with the involvement of vibrationally excited O₂* molecules, generated from the resonant exchange of vibrational energy with the H₂O* molecules, are considered.

This experimental work identifies spatial vortex parameters at the exit of the tangential swirler based directly on velocity distributions obtained by Stereo-PIV method with using pressure pulsations in the acoustic field of swirling jets. The velocity measurements are carried out for high swirl jet close to exit of swirler nozzle (Re = 23000 and Sh = 1.54). The spatial distribution of the PVC is captured with statistical analysis of instantaneous velocity fields and phase-averaged vorticity distribution.

The paper studies the loss of stability of a liquid film using regular surface roughness. The model of the breakdown process is described and the conditions for the formation of a liquid film breakdown are determined experimentally. It was found that there are two characteristic modes, namely drop and film regimes. Using the methods of thermal anemometry, data were obtained on the distribution of the droplet sizes after a film breakdown and the dependence of the We number on the projection arrangement height was plotted.

The paper submits a newly developed experimental setup and describes the flow arrangement for the best possible separation of a mixture of two immiscible liquids by a gravitational method. Separation of water and Exxsol D100 solvent has been studied experimentally.

The description of the experimental stand (laboratory regenerative air preheater), the method for measuring the unsteady flow temperature and the results of experimental heat transfer studies of a package of plates (nozzles) of alloy steel AISI-430 with a 2 mm thickness for short-time periods with different durations are presented. The experimentally obtained mean Nusselt numbers are generalized by the criterial equation.

The work is devoted to the study of the electrophysical properties of brown coal at the Talovsky deposit in Siberia. This type of coal can be successfully used as an energy fuel for thermal power plants, boiler houses and other industries. However, experiments show that like other low-quality coals, it needs additional treatment: drying, removing of toxic impurities, crushing, etc. Due to this, the search for the most optimal methods of its processing is constantly conducted. One of the promising methods? is the treatment with microwave radiation. This leads to intensive drying, removing of sulfur, nitrogen, mercury, chlorine and other undesirable impurities, grinding the fraction, which generally positively affects the quality of the fuel being prepared for use [1]. However, for the most effective use of microwave technologies, knowledge of the coal properties and their changes during processing is necessary. In particular, the dielectric properties of coal are responsible for the efficiency of microwave energy absorption. And due to changes in the humidity and temperature of the coal during microwave heating and drying, the efficiency of the process will always change. This work is devoted to the measurement of electrophysical properties and their dependencies.

The paper investigates the local thickness distribution of a wall liquid film in a curvilinear channel. The research technique on experimental water–air stand with a curvilinear working channel is described. The results of measurements of the local thickness of the liquid film on the upper and lower walls of the channel for two flow velocities are obtained at various flow rates.

The results of experimental study of structural integrity destruction of lithium-thionyl chloride batteries are provided in the article. The research methodology in non-standard situations was realized using the mechanical damage of the battery body integrity by impact of metal rod on the battery body. Battery charge impact assessment was held during the research process. Pressure change dependences in manometric bomb in the moment of explosion of lithium-thionyl chloride batteries are presented in the paper.

Due to the revival of the interest to the development of fast reactors cooled by liquid metals, it is important to provide theoretical research of reactor's safety. A detailed calculation of all stages of the accident from the beginning to the end requires knowledge of the laws for modeling of physical processes occurring in the reactor in an emergency. The most jeopardized are accidents with the destruction of the reactor core. The main objective of the proposed research is developing of models and numerical algorithms for calculation of core degradation. These models can be used in codes for analysis of severe accident in fast reactors. The presented paper contains descriptions of algorithms that are used to simulate melt motion on the surface of fuel pins.

Steam reforming of C₂-C₄ alkanes was studied in annular catalytic reactor under atmospheric pressure over Rh-(La₂O₃, BaO)-Al₂O₃ catalysts. Effects of temperature have been compared for different residence time. Concentrations of the products of chemical reactions in the outlet gas mixture are measured at different temperatures of reactor. It was found that the catalyst has good performance and provide equilibrium product distribution at GHSV = 30000–55000 h⁻¹.

In the paper, a building with walls filled with lightweight thermal insulation with a phase change material is considered. Numerical computations were made on the basis of a simple enthalpy model, and the effect of macro-encapsulated phase change material on the heat-inertial properties of walls under conditions of daily fluctuations in the temperature of the outside air was analyzed. The spatial arrangement of the phase-change material has been varied during the calculations, as well as the temperature of its phase transition. Analysis of calculation results shows that addition of a phase-change material allows not only to increase the heat-accumulating capacity of the building envelope, but also to control heat flows on the wall surfaces. As a result, it becomes possible to reduce the peak values of the heat flux on the inner surface of the wall, and also to provide a certain flow direction.

The results of physical and mathematical modeling of a new air heat exchanger with an intermediate heat carrier and with drip irrigation of granular layer are presented. The effects of the equivalent diameter of the granules, height of the layer and the heat transfer coefficient on the thermal effectiveness of the heat exchanger are analyzed. The results of an experimental study of the uniformity of the distribution of the heat carrier in the tower cross-section for various methods of granular layer irrigation are presented.

Algorithm of the direct simulation Monte Carlo method for the flow of the hydrogen-methane mixture through a cylindrical channel has been developed. Heterogeneous reactions on tungsten channel surfaces and gas-phase reactions are included into model. The influence of the channel length on the degree of hydrogen and methane dissociation in the gas mixture have been analyzed. The obtained results can be useful for optimization of gas-dynamic sources of activated gas diamond synthesis.

The effect of magnetron sputtering of an electrode on the chemical composition of a plasma of a spherical gas discharge is studied experimentally by mass spectrometry. The experiments were carried out in an apparatus for studying plasmochemical processes in a gas discharge of spherical geometry with a small anode. It was revealed that in the argon discharge, the molecules of the electrodes of both the vacuum chamber and the target of the magnetron are detected by mass spectrometry. It is not observed in the case of a spherically stratified gas discharge in ethanol which is explained by the confinement of molecules in the potential wells of the striations.

The influence of a monatomic carrier gas on cluster formation in supersonic methane jets is studied. The formation of methane clusters in a mixture with condensed argon and non-condensable helium with the same gas-dynamic parameters is then compared. It is shown that the methane clusters' formation intensity is extremely low both within a jet of pure methane, and in a mixture with carrier argon. The methane condensation process dependence on the properties of a carrier gas and the methane volume fraction in the mixture at the selected gas dynamic parameters of the flow is demonstrated. The effect of dissociative methane ionization and the fragmentation of methane clusters in the mass spectrometer detector on the recorded mass spectrum is established. The cluster methane ions protonation and the increase in their fraction with increasing clusters are recorded. Finally, magic numbers for methane clusters are found.

The possibility of using a high-voltage electron beam as an ionizer of supersonic clusters of argon and methane gas jets in molecular beam mass spectrometry are investigated. The formation of clusters occurs when the gas flows through the supersonic nozzle into the vacuum. The ionization of the flow is carried out by electrons with an energy of 10 keV. The diaphragm (skimmer) from jet forms a molecular beam, which passes into the input aperture of the mass spectrometer through the sections of the installation. The ion focusing is provided with the use of collimating diaphragms as electrostatic lenses. A quadrupole mass spectrometer is used as a cluster ion analyzer. The obtained mass spectra are compares with the signals observes with the usage of traditional molecular beam mass spectrometry, in which ionization of particles occurs in the electron analyzer's own block with energies of the 100 eV order. The justification of the standard approach shortcomings is proposed. Obtained data shows chemical reactions in hydrocarbons and cluster magic numbers for argon, obtained result is consistent with known data.

The study of free supersonic jets showed that the condensation process leads to the Van-der-Waals clusters formation. Supersonic flows clustering leads to a change of the first jet dimensions and to the formation of a secondary structure ("trace"). When the jet is ionized by an electron beam, this structure has a weakly fading glow outside the ionization region. The authors of this work explore the processes leading to the formation of this glow. The condensation influence on the background gas penetration into the jet, the energy exchange effect between jet particles and background particles, and particle lifetime in the "trace's" glow process are studied.

A brief review of the work carried out at the Institute of Thermophysics of the SB RAS on the use of supersonic jets in scientific research to obtain relaxation process constants is presented, such as, effective cross sections for quenching of electronic states, atoms, molecules and ions. Also a review of the work directed to the use of jets and electron beams in various plasma-chemical technologies is given, namely, deposition of functional layers of thin-film silicon solar cells and conversion of hydrocarbon gases into useful products.

Two-dimensional direct Monte Carlo simulation of neutral gas expansion under pulsed evaporation into vacuum has been performed. Analysis of temporal evolution of the spatially-averaged characteristics of the plume has been carried out for a wide range of the problem parameters: the spot radius and the evaporation depth. Special attention has been paid to determination of the limits of applicability of one-dimensional approach for gas dynamic simulation.

Low-frequency ferromagnetic-enhanced inductively coupled plasma (FMICP) has been investigated under conditions typical for large-scale plasma processing. Radial profiles of ion density and plasma floating potential were determined with a Langmuir probe. A self-consistent radial kinetic model of argon FMICP was developed, based on the simultaneous solution of a non-local Boltzmann equation for the electron energy distribution function, balance equations for the ion and metastable argon atom densities, the thermal balance equation and the Poisson equation for a self-consistent radial electric field. A satisfactory agreement between the numerical and experimental results was found that confirms the validity of the presented approach to the description of the FMICP.

The constructive schemes of electric-arc plasmatrons were analyzed by energy and erosion characteristics. The effect of arc shunting on plasmatron classification is presented. The effectiveness of barrier cooling in plasmatron channel with a sectioned interelectrode insert is determined. The criteria for the efficiency of tubular electrodes in plasmatrons with gas-vortex stabilization of an arc discharge are given. The role of vacuum plasmatrons in creation of plasma-vacuum electric furnaces is shown.

Experimental investigation of low-frequency (100 kHz) nitrogen inductively coupled plasma with magnetic coupling enhanced by ferrite cores has been carried out, for nitrogen pressures of 50–200 mTorr. Discharge electric field strength and ion density were measured for various discharge currents. Plasma-assisted nitriding of titanium test samples was performed for sample bias of -1200 V and sample current density of 1 mA/cm². Formation of hexagonal ω-Ti and tetragonal TiN phases was revealed.

The present work is devoted to a numerical and experimental investigation of the effect of methane decomposition conditions on the growth of diamond structures during gas-jet deposition.The results of experiments on the diamond gas-jet synthesis from methane and hydrogen mixture flows are presented. The direct simulation Monte Carlo method in cylindrical geometry for numerical analysis of these experiments was applied. A one-dimensional approach based on the solution of equilibrium chemical kinetics equations was used to analyze gas-phase methane decomposition. The conducted researches have shown that at decrease in time of decomposition of methane in absence of high temperatures of the fed mixture it is possible to receive higher rates of growth of diamond structures. The obtained results can be useful for optimization of gas-dynamic sources of activated gas diamond synthesis.

Non-equilibrium effects of different nature and their impact on the reaction and relaxation rates of the reacting gas mixture are considered. Expression for the dissociation rate is obtained employing the asymptotic method of solving Boltzmann equation, developed in the previous papers (Kolesnichenko, Gorbachev, 2010, 2013, Gorbachev 2016). Application of the projection method for solving the integral equations for zeroth-order corrections to quasi-equilibrium distributions is examined. Possibilities of simplifying of the expressions for reaction rates are discussed.

The algorithm for computation of the transport coefficients of rarefied gas is suggested. It is based on stochastic modeling of phase trajectories considered molecular systems. The Lennard-Jones intermolecular interaction potential is used. The number of operations is proportional to the number of used molecules. Naturally in this algorithm the conservation laws are performed. The efficiency of the algorithm is demonstrated by the calculation of the viscosity coefficients of several noble gases (argon, neon, xenon, krypton) and polyatomic gases (nitrogen, carbon dioxide, methane and oxygen). It was shown that the algorithm accuracy of the order of 1-2% can be obtained by using a relatively small number of molecules. The accuracy dependence on the number of used molecules, statistics (the number of the used phase trajectories) and the calculation time were analyzed.

A self-consistent non-local model of the positive column of a dc glow discharge in helium, neon and argon with dust particles is presented. A kinetic Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions and dust particles, the Poisson equation for electric field were calculated self-consistently for different discharge conditions. The radial distributions of the discharge plasma and the dust particles parameters were obtained for different discharge gases. The influence of the buffer gas sort is revealed and discussed.

The nonequilibrium processes in flows of gas mixtures on the way to surface, where diamond structures formation takes place, are discussed. The main attention is focused on processes with thermal activation. Thermocatalitical phenomena in the collision of hydrogen and methane molecules with tungsten, nonequilibrium processes during transportation of active components in channels and on the way to the substrate, formation of gas atmosphere immediately close to the surface of diamond formation – all these processes relate to the field of modern physical mechanics. This statement can be related to the diamond synthesis from microwave plasma which is determined by generation of plasma from high frequency radiation and in most cases diffusion interaction of plasma with surface of deposition. The main content of studies in the Institute of Thermophysics belongs to a new direction of research, to synthesis of diamond from high velocity flow of gas mixtures or plasma.

The effect of various activator materials on the structure and properties of fluoropolymer coatings was studied using hexafluoropropylene oxide as the precursor gas. Nichrome, nickel and tungsten wires were used as catalysts. Coatings were obtained on various materials: stainless steel, copper, glass and silicon with different structures that can be used for practical applications.

The temperature distribution for one drop on a horizontal heated constantan foil is investigated. The temperature distribution for different time moments of the bottom foil surface was measured by the FLIR infrared (IR) camera. In the future the heat flux distribution near the contact line of drop will be calculated by numerical solution of the Cauchy problem.

The results of experimental studies of the microsuspensions filtration with silicon oxide nanoparticles additions through a porous medium with different permeability are presented. The particle concentration in fluids ranged from 0.25 to 4 wt.%. The microparticle size was 1.2 μm. The nanoparticle size was 5 nm. The nanoparticle concentration was 2 wt.%. Dependences of the filtration losses of microsuspensions on the microparticle concentration and the permeability of a porous medium were established.

The heat transfer in a shear driven rivulet flow at isothermal conditions in a minichannel has been studied. The experiments were conducted using the setup, specially designed for the shear driven rivulet flow. The effect of liquid flow rate and substrate temperature on the width of the rivulet was studied experimentally using Laser induced fluorescence technique (LIF). The temperature distribution for different time moments of the rivulet surface was measured by the FLIR infrared (IR) camera. IR-measurements served to demonstrate that rivulet surface temperature is lower than substrate one due to liquid evaporation from the rivulet surface.

The technology of solid-state light source is associated with the future of a number of sectors of economy. Duration of failure-free operation, optical radiation power and other output characteristics of the LEDs are closely linked with p-n junction temperature, which makes the development of the cooling systems an important step in creating LED systems. In this work, we have created a new type of thermosiphon for studying heat transfer from a local heat source. Boiling heat transfer on the local heaters with the diameter of 1 and 5 mm has been investigated. It is shown that on the finned surfaces overheating relative to the saturation temperature in comparison with a smooth surface decreases up to three times for the heater with the diameter of 5 mm. For finned surfaces on the heater with a diameter of 1 mm, surface overheating relative to the saturation temperature decreases four times. More than three times increase is observed for the heat transfer coefficient on finned surfaces as compared to the smooth ones. It is shown that the value of the critical heat flux (CHF) under the conditions of a large volume of liquid for the heaters with D = 1.6 and 5 mm is in good agreement with the known dependences. Radial finning of the heater has no effect on CHF. The value of CHF for D = 1 mm turns out to be higher than the calculated one. The greatest increase is achieved by using a head with finning.

The known variants of deposition of thermal barrier coatings (TPC) of ZrO2-Y2O3 by the MO CVD method are analyzed. It is established that the use of this method in principle allows obtaining ceramic coatings with the required columnar structure, low thermal conductivity and technologically acceptable growth rates. It is shown that the main limiting factor in the coating growth rate is the productivity of the precursor vapor sources used. The analysis of known variants of realization of heat and mass transfer at the use of various precursors with a wide range of thermal parameters for the given process is carried out. The results of experimental studies and numerical modeling of the kinetics of sublimation of a number of precursors in the flow of an inert gas Ar, He or their mixtures in a given range of temperatures and gas flow rates are obtained. It is established that when sublimating a single precursor particle under forced convection, the mass transfer intensity of a given compound in the helium stream is several times greater than mass exchange in argon with other closely related parameters, such as the flow velocity and the temperature of the oncoming flow. At the same time, the temperature of the particle is lowered, which can be an important factor in increasing the thermal stability of the vapors. It is shown that there is an additional possibility to control the sublimation of the precursor with the Ar/He mixture.

A new method has been developed for the plasmochemical deposition of hard protective silicon carbonitride coatings from a hexamethyldisilazane (HMDS) Si₂NH(CH₃)₆ vapor and HMDS+ benzene activated by a powerful optic pulse discharge (POPD) in a high-velocity gas flow of argon. The method allows depositing silicon carbonitride coatings with a rate of 0.5−1.2 μm·min⁻¹ that is (1−5)·10² times higher than in conventional CVD processes. It has been found that coating deposition rate and structure of coatings depend on the process parameters: flow rates of HMDS and HMDS+benzene and plasma generating gas (argon). The method allows depositing SiCN coatings containing Si–C, Si–N and Csp³–N bonds with high velocity and microhardness 24 GPa.

Morphology, structure and surface composition of the synthetic polycrystalline diamond films grown by a gas-jet deposition have been studied with help of scanning electron microscopy, Raman scattering, X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. The diamond films were deposited from a high-speed jet of activated CH₄ + H₂ gaseous mixture on the Mo substrates heated to 900 °C with CH₄ flow rate of 8 sccm and 1000 °C with 12 sccm of CH₄. The high concentration of CH₄ in gas flow and the high substrate temperature resulted in an increase in the size and improvement of quality of the diamond crystals. A presence of sp² hybridized, hydrogenated and oxygenated carbon atoms on the surface of diamond films was revealed.

The turbulent forced convection of nanofluids with ZrO₂ nanoparticles in a channel with artificial roughness was experimentally and numerically investigated. Nanoparticle concentration in the experiments was equal to 4 vol. %. The nanoparticle size ranged from 44 to 105 nm. Numerical simulation of turbulent forced convection of nanofluids in a channel with annular knurls was carried out. A homogeneous model with experimentally determined transport coefficients was used to describe the nanofluid.

The production of a high-quality surface of fused silica is an important task for advanced optical technologies. In this work, the surface of fused silica has been processed by argon cluster ion beam having mean cluster size N_mean ranged from 180 to 1000 atoms/cluster and energy E ranged from 5 to 23.5 keV. The analysis of surface morphology using atomic force microscopy and the spectral power density (PSD) function shows a noticeable smoothing of roughness in different spatial frequency ranges, depending on the cluster ion parameters. To evaluate the processing efficiency, the dependence of the etching rate of SiO₂ on the parameters of cluster ions has been investigated. It is shown that the etching rate v_etch is determined by the energy per atom in the cluster E/N_mean and it varies from 0.2 to 20 nm/min with an energy change from 5 to 130 eV/atom.

The method of electric arc synthesis is used to obtain nanoparticles encapsulated in a carbon matrix. The properties of the entire material depend on the properties of the carbon matrix. In this paper, the structural characteristics of a carbon material synthesized at various arc discharge parameters are investigated. It is established that in the arc discharge a material containing amorphous and graphite-like carbon structures is synthesized, including in the form of graphene fragments folded into stacks, twisted into rolls and in the form of closed forms. Interplanar distances in graphite-like structures and interatomic distances in amorphous structures are determined. It is established that the pressure of the buffer gas determines the size of the soot globules and the volume fractions of graphite-like and amorphous structures, and the current strength affects the internal structure and determines the size of graphene planes in graphite-like structures.

The method of producing nano-dimensional silicon powders from monosilane pyrolysis by compressing in a cyclic process in the flow reactor has been proposed and implemented. The resulting powder has been examined by X-ray diffraction and electron microscopy. The new design solutions and ceramic coatings obtained by using microarc oxidation for the piston-cylinder assembly – a compression unit of the reactor, allowed avoiding the use of compression rings and lubricants and achieving high compression ratio, pressure and temperature in the reactor needed for monosilane pyrolysis. Pyrolysis in the flow reactor is convenient, technological and efficient to be used in the production of high purity silicon nanopowders.

Droplet-based cooling systems require a detailed data on droplet evaporation at relatively high substrate temperature. We investigate the dynamics of water droplet evaporation on a heated sapphire substrate for the substrate temperature of 408 K. The stable (not boiling) evaporating droplet of 0.33 μl volume forms immediately just after boiling process when the temperature is still higher than boiling temperature of the liquid. Stick-slip motion is observed with the first depinning at 0.07 μl in volume. Total evaporation time is 1.13 sec.

Structured arrays of liquid microdroplets levitating over the surface of hot liquid have been observed in several recent experimental works, however the nature of this phenomenon is still not completely understood. In the present paper, we study the peculiarities of formation and evolution of a structured monolayer consisting of several thousands of microdroplets levitating over the water film heated from below. It was found that with the increase of the substrate temperature, the number of droplets in the monolayer increases to a certain value, after which the number practically does not change. The size of the monolayer increases linearly with temperature from approximately 1 mm to 3 mm. The average distance between the microdroplets increases with the substrate temperature, with the droplet size, and also with the distance from the center of the monolayer.

This work is devoted to experimental studies of the effect of synthesis conditions on formation of single-layer graphene on the copper surface. Under the conditions of formation and growth of single-layer graphene, it is shown that characteristic times of graphite nuclei formation are about 1 min and times of primary layer growth are about 0.5 min. The subsequent layers form in 10 min. It is shown that hydrogen concentration at the initial stage of synthesis affects the growth rate of the second layer significantly.

Development of the modern microelectronic equipment requires the effective cooling solutions because it is necessary to remove high heat fluxes of up to 1 kW/cm² and higher from the local hot spots of the processor. Thin and ultra-thin (less than 10 μm in thickness) liquid films, moving under the action of a forced gas flow in a mini-channel, are promising for the use in the temperature control systems of the modern semiconductor devices. Here we report results of systematic experimental studies of the flow and rupture of a water film, shear-driven in the channel, under intense heating from a local heat source with size of 1x1 cm². To carry out high-speed visualization of the process, the FASTCAM SA1.1 CCD camera is used (with the speed of up to 100 000 frames per second). The camera is equipped with an optical system of high spatial resolution (2.5 μm per 1 pixel of the camera sensor). With the help of high-speed imaging, it was found that the maximum intensity of heat removal from the heater is achieved in the mode, when the film flow continuity is broken. The heater is covered with dry spots having typical size on the order of 10-100 μm and typical lifetime on the order of 0.1-1 ms. At that, the number of dry spots that exist simultaneously on 1 cm² of the heater surface can reach several hundred. During 1 s up to 1 million dry spots appear and disappear at the area of the heater.

Arrays of multi-walled carbon nanotubes (MWCNTs) were grown vertically on the surfaces of SiO₂/Si substrates using aerosol-assisted catalytic chemical vapour deposition (CCVD) method. Aerosol was produced by injecting a solution of ferrocene (catalyst source) in toluene (carbon source) into a hot zone of a horizontal CVD reactor. Dependences of the height and density of the MWCNT array on the synthesis temperature and ferrocene concentration were determined. The found optimal parameters were used for the MWCNT growth on copper substrates. For this purpose, a copper foil was covered by alumina layer and we showed that the thickness of this layer should be not less than 17 nm to provide the MWCNT growth over the entire foil surface. The vertically aligned MWCNT array tightly bonded with copper substrate can be used as a heat-exchange surface in various micro and nano heat-transfer devices.

With the help of advanced optical system having high spatial and time resolution, the dynamics of microbubbles was investigated during nucleate boiling of subcooled water flow in a mini-channel under localized heating from the wall. Substantial discrepancy in maximum bubble diameters was observed for the same experimental conditions. However, the growth rate for different bubbles within first 0.1 ms of their life time is almost the same. The data on the bubble dynamics was successfully generalized using available correlations from the literature. Data on the critical heat flux was obtained for different channel heights. A considerable effect of the channel height on the critical heat flux was found.

The fluoropolymer coatings with different structures on the layers of single-walled carbon nanotubes were deposited by the method of hot wire chemical vapor deposition. The layers of single-walled carbon nanotubes of different orientations were made by doctor blade method from an aqueous dispersion, containing 0.1% Tuball™ The influence of the singlewalled carbon nanotubes' layers on the structure and growth rate of the deposition of the fluoropolymer coatings was investigated. It has been shown that fluoropolymer coatings deposited on differently orientated single-walled carbon nanotubes' layers keep their hydrophobic and superhydrophobic properties, which are specific for them at depositing on a smooth silicon surface.

This paper presents an experimental study of evaporation of a millimeter-sized sessile water droplet into open atmosphere in a wide range of the temperature difference (from 0 to 76 K) between the solid substrate and the atmosphere. The study was performed using two substrates made of copper. One of them had no coating and was polished to the root mean square roughness of about 20 nm. Another one was coated with a micrometer-thick film of single-walled carbon nanotubes. With the help of precise drop shape analysis system, the mode of droplet evaporation with pinned contact line was studied. No appreciable difference was detected in evaporation droplet dynamics between the two substrates for the substrate temperatures from 24 to 100 °C.

The problem of radiation-conductive heating and subsequent melting of ice in a climatic chamber in a single-phase approximation of the Stefan problem with allowance for the emerging thin water film on the irradiated surface was solved by mathematical modeling methods. Fields of temperature and flux density of the resulting radiation are obtained, as well as the rate of melting and heating of the non-irradiated ice surface. Comparison with experiment showed satisfactory agreement.

The work is devoted to a search for regularities that allow predicting the heat transfer coefficients of metallic melts and their thorough testing.

Thermal conductivity of nanofluids has been modeled by means of molecular dynamics method. Nanofluids based on argon with aluminum and zinc particles ranging in size from 1 to 4 nm and particles volume concentration from 1% to 5% have been considered. The dependence of the thermal conductivity coefficient of nanofluids on volume concentration of particles has been studied. It was shown that the thermal conductivity of nanofluid is not described by the classical theories. It depends on the particle size and increases with it. In addition, it has been found that nanofluids with small particles may have even lower thermal conductivity than that of the base fluid. Evolutions of correlation functions that contribute to the thermal conductivity coefficient and integrals from them were studied in details.

The speed of sound of the gaseous mixture of R-134a and R-227ea (30.73 / 69.27 mass.%) was investigated by an ultrasonic interferometer over the temperature range of 293–373 K and at pressures from 0.12 MPa up to 1.3 MPa. The measurement errors for the temperature, pressure, and speed of sound were estimated at 20 mK, 4 kPa, and 0.1–0.3%, respectively. The approximation dependences for the speed of sound in the vapor were obtained and their errors were estimated. The obtained data were compared with the results of calculations by the REFPROP software.

The paper is devoted to simulation problem of heat transfer in vacuum shaft electric resistive furnace with combined insulation. Concept of critical diameter of cylindrical combined thermal insulation is explained. Physical-and-mathematical model for investigation of interconnection of geometrical and thermophysical parameters of the combined thermal insulation with heat flow through it is proposed. Dependences of effective heat transfer coefficient of screen partition of the combined thermal insulation and effective critical diameter of the insulation partition of the combined insulation upon its geometrical and thermophysical parameters are uncovered.

The results of a dilatometric study of the linear thermal expansion coefficient (LTEC) of polycrystalline terbium within the temperature range of 110–800 K are presented. The measurements were conducted with an error (1.5−2.0) × 10⁻⁷ K⁻¹. Approximate dependencies which allow calculating the reference tables of volumetric properties for the entire measurement interval were obtained. The character of the change in the linear thermal expansion coefficient in the vicinity of the Curie and Neel points is established. Critical exponents of the LTEC for two magnetic phase transitions were defined.

Results of thermodynamic modeling of radioactive graphite-nitrogen system heating which can be applied as reference data and can be used in technological processes of high-temperature processing of reactor graphite are given in the article.

The molecular dynamics calculations of diffusion coefficients in binary Lennard-Jones liquids have been carried out. The change of diffusion mechanism has been observed with transition from dense gas to liquid. The diffusion mechanism in liquids isn't connected with jumping motion of molecules. A good agreement between our results and the experimental data for krypton diffusion in liquid argon has been obtained.

The method of controlled pulse heating of a wire probe – resistance thermometer in thermal stabilization and constant heating power modes was used for the study of heat conduction of liquid binary solutions in stable and superheated conditions. The objects of the study were aqueous glycol solutions (ethylene glycol, diethylene glycol and triethylene glycol) with negative excess volume. The values of thermal resistance and thermal conductivity coefficient of the solutions, calculated using the primary data of pulse heating experiment were compared with the values of excess volume of the solutions. A correlation was found between the thermal conductivity of the solution and the value of its excess volume for the temperature range studied.

The experimental setup and the variant of calculation-experimental technique of measuring the emissivity coefficient of heat-shielding materials surface are presented.

The results of the thermal conductivity measurements of ten mixture refrigerants in the gas phase are analysed. An equation for calculating the thermal conductivity is given for each mixture as a function of temperature and pressure. Basing on experimental information and the theory of of corresponding states a model for predicting thermal conductivity on dew line is proposed.

Heat capacities C_v, C_p and sound velocity W of carbon dioxide are calculated basing on the new thermal equation of state (EoS) with a small number of regulated constants. This equation includes a new regular EoS with 11 coefficients and scaling EoS with six coefficients and regular transition function containing two adjustable parameters. The results of calculating the thermodynamic properties of CO₂ in the regular behavior range of up to 200 MPa correspond to the accuracy level of the modern reference equations of state. To determine the constants of the calculated equations, only p,ρ,T -data for CO₂ were used. The average error in describing the thermal properties of CO₂ does not exceed the error of the available experimental data. The calculated values coincide with the values of the reference data.

A simple unified low-parametric equation has been obtained for describing the coefficient of argon and xenon viscosity in a wide range of state parameters. It is shown that the proposed low-parametric equation for calculating the viscosity coefficient of liquid and gas allows reliable extrapolation beyond the studied region.

Thermal conductivity of the gaseous R-227ea/R-134A (45/55) mixture was investigated by the coaxial cylinders method within the temperature range of 306–426 K and the pressure range of 0.1–1.6 MPa. Approximating dependence of thermal conductivity on pressure and temperature was obtained. Thermal conductivity on dew line and in ideal gas state was calculated.