Volume 95, №2


CALCULATION OF HEAT EXCHANGE FOR VARIABLE-HEAT-CAPACITY FLOWS

The authors have obtained minimum conditions for the irreversibility and the contact surface of double-fl ow heat exchange with a prescribed total heat load with various constraints imposed on the set of permissible fl ow temperatures. Consideration has been given to fl ows with a constant heat capacity and to fl ows with a temperaturedependent heat capacity and, in particular, changing their phase state, that are of arbitrary high heat capacity at the boiling/condensation point. It has been shown that the obtained relations yield the existence of realizability limits of the process and relations have been derived to calculate them. For variable-heat-capacity fl ows, the entropy production in their mixing has been obtained  
Author:  A. M. Tsirlin , L. G. Gagarina
Keywords:  double-fl ow heat exchange, irreversibility, contact surface, heat load, entropy production
Page:  283

PALEOTEMPERATURES OF THE EARTH′S SURFACE. 1. DETERMINATION OF THE AVERAGE ANNUAL TEMPERATURE OF THE EARTH AND HEMISPHERES

The author has presented functional dependences to determine the distribution of the average annual temperature and annual insolation alog an Earth latitude  
Author:  I. I. Smul′skii
Keywords:  midlatitude temperature, annual insolation, paleoclimate
Page:  291

PALEOTEMPERATURES OF THE EARTH′S SURFACE. 2. DETERMINATION OF THE MIDLATITUDE NEAR-SURFACE HEAT-CAPACITY OF THE EARTH

Two methods have been proposed for calculating the midlatitude near-surface heat-capacity of the Earth: 1) using the latitude variation of the Earth temperature, and 2) using the insolation of the Earth in the modern epoch and its variation with time. Using the obtained values of this heat capacity, profi les have been determined for the midlatitude paleotemperatures of the Earth in three extreme epochs in the past 50 thousand years, and the evolution of the paleotemperature in the past 200 thousand years has been calculated.  
Author:  I. I. Smul′skii
Keywords:  midlatitude temperature, insolation, heat capacity, paleotemperature, paleoclimate.
Page:  299

ACCUMULATION OF ISOTOPE MIXTURE COMPONENTS IN A SEPARATION CASCADE

Numerical investigations have been conducted into the process of separating a multicomponent isotope mixture in a cascade. Regular patterns have been established for the effects of the cascade parameters on the component concentration value in the cascade gas content. Conditions have been identifi ed under which the maximum quantity of the target component is accumulated in the cascade. The investigation results can be used for further study of unsteady processes of accumulating isotope mixture components in a separation cascade.  
Author:  A. A. Ushakov , A. A. Orlov , V. P. Sovach
Keywords:  multicomponent isotope mixture, isotope separation, isotope enrichment, fi ne purifi cation of substances, computer modeling of separation processes
Page:  309

CORRECTION OF SIGNALS IN A MICROBOLOMETRIC ARRAY RAISING THE VALIDITY OF MEASURING OBJECTS′ TEMPERATURE. PART 2

Consideration has been given to methods of accounting for the effects of deviation of the temperature of the array sensitive elements from the values registered during the conduct of calibration and also from the effective thermal emissivity of the controlled bodies and the heat radiation of the ambient environment refl ected from them on the calculated values of the temperature fi eld being formed.  
Author:  V. A. Firago
Keywords:  thermal imaging signals, radiation, temperature fi elds, measurements
Page:  316

NUMERICAL SIMULATION OF THERMOELECTRONIC THERMAL PROTECTION IN THE CASE OF HIGH ENTHALPY FLOW PAST A MULTILAYER SHELL

A mathematical model of the process of unsteady conjugate heat transfer of a thermionic thermal protection system during supersonic air fl ow around a spherically-blunted cone is investigated. Estimates of the effect of evaporation (emission) of electrons from the emitter surface on lowering the temperature of the composite shell of the thermoelectronic thermal protection are made. The infl uence of different angles of attack on heat transfer modes in the system of multielement thermionic thermal protection has been studied. Qualitative agreement of calculated results with the known data has been found.  
Author:  K. N. Efimov  , V. A. Ovchinnikov , A. S. Yakimov
Keywords:  thermoelectronic thermal protection, emitter, collector, heat transfer, cooler
Page:  327

SIMULATION OF THE CONVECTIVE HEAT TRANSFER IN A SPHERICAL ELECTROCONDUCTIVE LIQUID LAYER WITH HEAT SUPPLY AND HEAT REMOVAL

Results of a numerical simulation of the nonstationary heat transfer in the layer of an electrically conducting liquid between two concentric spheres are presented, the infl uence of the internal heat sources in this layer on the structure of the liquid fl ow, the temperature and magnetic induction fi elds, and the distribution of Nusselt numbers in it was investigated  
Author:  S. V. Solov′ev
Keywords:  mathematical simulation, nonstationary heat transfer, magnetic hydrodynamics, spherical liquid layer, internal heat sources
Page:  343

INFRARED DRYING OF A PLATE IN A CONTINUOUS ELECTROMAGNETIC FIELD

Absorption of electromagnetic energy by a plate in an infrared frequency range is considered. A linear problem (constancy of process parameters) of infrared heating of the plate under conditions of convective heat and mass transfer of its surface with an external gas medium is formulated and solved analytically both for the general process of drying and for drying in the fi rst period. In formulating the heat conduction problem, it is assumed that the internal heat source caused by the absorption of radiant energy is distributed exponentially over the plate thickness and that phase transformations during moisture evaporation occur near the plate surface. The drying intensity is described on the basis of the analytical solution of the linear (constancy of mass conductivity) problem of mass conductivity (diffusion of moisture) for the plate under the boundary condition of mass transfer of the third kind. Solutions of the problems of heating are obtained in relation to local and body volume-averaged temperatures. They are used as the basis for numerical simulation of the process of heating a plate with account for its drying: the infl uence of the drying intensity and radiant fl ux density on the plate heating dynamics is shown. As applied to the fi rst period of drying, it is shown that the particular solution obtained in this case for the problem makes it possible to calculate the drying intensity, as well as the local and volume-averaged temperatures of the plate under the conditions of infrared energy supply. The article presents the procedure of determining the drying intensity in the fi rst period with the use of the Antoine equation for calculating the saturated vapor pressure near the plate surface from the plate surface temperature determined from the solution obtained  
Author:  S. P. Rudobashta , É. M. Kartashov , G. A. Zueva
Keywords:  drying, infrared (IR) heating, convective heat and mass transfer, analytical solution
Page:  357

WAVE HEAT TRANSFER IN ANISOTROPIC HALF-SPACE UNDER THE ACTION OF A POINT EXPONENTIAL-TYPE HEAT SOURCE BASED ON THE WAVE PARABOLIC-TYPE EQUATION

Based on the generalized law of wave heat transfer, a wave equation of parabolic type is obtained, for which the problem of heating an anisotropic half-space under the action of a point nonstationary source of thermal energy of exponential character is posed and solved analytically. The anisotropic half-space has anisotropy of heat transfer in planes parallel to the plane bounding the body, whereas the body is isotropic in the direction of the axis perpendicular to these planes. Therefore, the isotherms moving in time have the form of elliptical paraboloids, at the fronts of which the fi rst-kind discontinuous changes are observed in both temperatures and heat fl uxes, which is a consequence of the wave nature of heat transfer. Numerical results are obtained and analyzed  
Author:  V. F. Formalev , É. M. Kartashov , S. A. Kolesnik
Keywords:  wave heat transfer, anisotropy, relaxation time, parabolic-type wave equation, principal axes and components of the thermal conductivity tensor, nonstationary temperature field
Page:  366

TOWARD THE SOLUTION OF INVERSE THERMAL CONDUCTIVITY AND THERMAL ELASTICITY PROBLEMS

The article describes a method of solving inverse problems, which is based on the joint application of the A. N. Tikhonov regularization principle and of the method of infl uence functions that play an important role in obtaining stable solutions of ill-posed problems and in facilitating the computational process due to the preliminarily determined infl uence functions. The method is the result of development of the methodology previously developed by the authors for solving inverse problems, which is based on the various methods of regularizing solutions to multiparameter ill-posed problems of fi eld theory, as well on the experience in identifying the parameters of mathematical models of various levels. The results of identifi cation of heat transfer at the boundary of a body by displacements measured with an error characterized by a random variable distributed by the normal law are presented. The proposed method makes it possible to use experimental information obtained from several sensors. It is applicable to the study of heterogeneous media and combines the simplicity of programming with the ability of parallelizing the computational process, which meets modern requirements for methods and algorithms of solving direct and inverse problems.  
Author:  Yu. M. Matsevityi , E. A. Strel′nikova , V. O. Povgorodnii , N. A. Safonov , V. V. Ganchin
Keywords:  inverse problem, thermal stresses, regularization, infl uence functions, identifi cation, stabilizing functional
Page:  374

RATIONAL THERMODYNAMIC PARAMETERS OF MULTISTAGE POWER CYCLES APPROPRIATE FOR LOW-TO-MODERATE GEOTHERMAL RESOURCES

The geofl uid temperatures of the most promising geothermal areas of Ukraine are estimated to be less than approximately 130oC. This paper presents the results of a theoretical design study on the thermodynamic cycle parameters of a geothermal power station that would utilize these geothermal resources, and these results are similar to ones given elsewhere. Various confi gurations of the organic Rankine cycle (ORC) are considered. Thermal schemes of 3-stage geothermal power installations are studied. The effectiveness of geothermal power stations with various working fl uids at each stage is investigated. The results of a numerical study of the thermal 3-stage geothermal installation schemes show that at a geothermal liquid temperature of 130oC the possible total specifi c power output of a turbine is 20.7–20.8 kW per kg/s of a geofl uid flow. The combined 3-stage cascaded system with a bottoming cycle can generate about 15% more power than a simple single-stage binary plant at the same brine inlet conditions  
Author:  A. Redko , O. Redko ,  N. Kulikova , S. Pavlovskyi , R. DiPippo
Keywords:  geothermal power, organic Rankine cycle, 3-stage cycle, thermal effi ciency, utilization effi ciency, geothermal areas of Ukraine
Page:  380

ANALYSIS OF THERMAL PERFORMANCE, EFFICIENCY, AND EFFECTIVENESS OF A STRAIGHT POROUS FIN WITH VARIABLE THERMAL CONDUCTIVITY

Radiating extended surfaces are generally used to reinforce heat transfer between a primary surface and its environment. Specifi cally, if great temperature contrasts are taken into account, variable thermal conductivity materially affects the performance of the system. Thus the present numerical study is concerned with the thermal performance of a straight porous fi n under the infl uence of temperature-dependent thermal conductivity, magnetic fi eld, and radiation. The heat transfer model, which includes the Darcy law for simulating fl ow with solid–fl uid interactions in a porous medium, the Rosseland approximation for heat transfer through radiation, the Maxwell equations for the magnetic fi eld effect, and linearly varying temperature-dependent thermal conductivity, results in a highly nonlinear ordinary differential equation solved with using the fi nite-difference scheme with suitable boundary conditions. The obtained solutions are interpreted physically by considering the impact of relevant nondimensional parameters on the thermal performance, effi ciency, and effectiveness of the system. It follows from the analysis that the temperature-dependent thermal conductivity improves these characteristics  
Author:  Babitha , K. R. Madhura
Keywords:  straight porous fi n, temperature-dependent thermal conductivity, magnetic fi eld, fi nite-difference method, Rosseland approximation
Page:  392

LABORATORY MODELING OF THE PROCESSES OF SOUND EXCITATION BY SELF-OSCILLATING REGIMES IN FLOWS IN HEAT-EXCHANGE-SYSTEMS' PIPELINES

The authors have performed laboratory modeling of noise-emission processes in turbulent fl ows of the heattransfer agent in shutoff and control valves of a pipeline. Experiments were conducted on an aeroacoustic bench consisting of a model of the fl ow chamber of shutoff and control valves (parallelepiped), inlet and outlet tubes, an exhaust fan, and a baffl e chamber. Parallel measurements of velocity fi elds were performed by the PIV method, and of acoustic characteristics, with a microphone. The experiments were conducted with different widths of the gaps between the tubes in the fl ow-chamber model. At certain values of the gaps, tone sounding was recorded at frequencies of 340 and 680 Hz by the microphone, which, as subsequently shown by results of the velocityfi eld measurements, is a consequence of the self-oscillating fl ow regime occurring with a periodic separation of vortices whose scale is comparable with the gap width in the fl ow chamber  
Author:  D. A. Sergeev , A. A. Kandaurov , A. V. Stulenkov , A. S. Suvorov
Keywords:  self-oscillations, fl ows in pipelines, sound, laboratory modeling
Page:  402

FLOW DYNAMICS AND ACOUSTICS OF THE GAS JET EMANATING FROM A CONICAL NOZZLE INTO AN IMMERSED SPACE

The subsonic and supersonic gas jets emanating from a conical nozzle into an immersed space were investigated. The infl uence of the difference between the total pressure at the inlet of the nozzle and the static pressure in the surrounding medium on the structure of such a jet and its fl ow dynamics and acoustics were determined and the noise level in the far fi eld of the jet was calculated. The results of numerical simulation of the outfl ow of a gas from a conical nozzle into an immersed space were compared with the corresponding experimental and calculation data available in the literature. The methods developed for numerical simulation of the fl ow dynamics and acoustics of gas jets can be used for solving different research and engineering problems as well as for development of new computational algorithms  
Author:  K. N. Volkov , V. N. Emel'yanov , P. S. Chernyshov
Keywords:  computational gas dynamics and aeroacoustics, supersonic underexpanded jet, noise, conical nozzle
Page:  409

INVESTIGATION INTO THE PROCESS OF INTERACTION OF THE LIQUID AND THE GAS IN A JET-FILM CONTACT DEVICE

With the aim of increasing the capacity of commercial cooling towers and enhancing heat-transfer processes, the authors have developed a structure of a jet-fi lm contact device. An experimental setup was assembled that permits investigating the hydrogasdynamics of a liquid in the operating region of the device. Results of investigation into the infl uence of the fl ow rate of the liquid and the gas on the hydraulic resistance of the contact device have been presented. A mathematical dependence has been obtained for calculating the pressure difference of a dry packing of the jet-fi lm contact device on the velocity factor. It has been established that with increase in the water concentration, the hydraulic resistance changes only slightly, which is a great advantage among the existing structures. The heat output of a cooling tower has been determined; the criterion of energy effi ciency has been considered which takes account of the expenditure of energy to pump air. The high energy effi ciency of a jet-fi lm contact device compared to various types of water-cooling devices has been proved  
Author:  A. V. Dmitriev , M. M. Farakhov , A. I. Khafi zova , O. S. Dmitrieva , I. N. Madyshev , A. D. Gilyazov , A. A. Akhmitshin
Keywords:  contact device, mass transfer, hydraulic resistance, energy efficiency
Page:  421

MATHEMATICAL SIMULATION OF HEAT TRANSFER AND CHEMICAL REACTION IN A SWIRLING FLOW OF EQUILIBRIUM-DISSOCIATING GAS

Results of investigations of the heat transfer in the swirling turbulent fl ow of dinitrogen tetroxide in a cylindrical channel are presented. The equilibrium stage of the dissociation reaction N2O4 ⇄  2NO  was considered. It was established that the mass fraction of N2O4 in its swirling fl ow is smaller than that in the analogous forward fl ow at one and the same distance from the input cross section of the channel. In the case where the fl ow of dinitrogen tetroxide is strongly swirled, its intense heating in the zone of reverse fl ows near the channel inlet causes it to dissociate. It is shown that an increase in the swirling of a gas fl ow intensifi es the heat transfer in it with increase in its Nusselt number  
Author:  O. V. Matvienko , P. S. Martynov
Keywords:  heat transfer, chemical reaction, dissociation, boundary layer, swirling fl ow, computational fl uid dynamics
Page:  428

EXIT DEVICES WITH RESONATORS-THRUST AMPLIFIERS FOR JET ENGINES

The authors have presented results of investigations into the exit devices of jet engines with resonators-thrust amplifi ers. The infl uence of the size of a resonator cavity, and also of the temperature and the gas constant on the effi ciency of buildup of the thrust of the exit device with a resonator has been determined. A study has been made of the possibilities of augmenting the effective thrust of the jet engine with a resonator exit device. The possibility of creating exit devices of increased size with the effect of amplifi cation of the thrust of the exit device with resonators of various types has been analyzed  
Author:  V. I. Bogdanov , D. S. Khantalin
Keywords:  exit device, resonator-thrust amplifi er, weight-size characteristics, added mass, gas constant
Page:  441

HIGH-VELOCITY PENETRATION INTO A METAL BARRIER BY A VISCOELASTIC ROD

A model has been proposed for a high-velocity interaction of a viscoelastic rod with a barrier resulting in ejecting a plug in a target. We have obtained an approximate analytical solution of a problem, in which the deformation of the striker and the target is considered jointly, and a relation that associates the barrier penetration time with the plug mass, the critical shear strength of the target, and the striker parameters in the case when the plug after-penetration velocity is equal to zero  
Author:  A. Yu. Algabachiev , N. N. Kholin
Keywords:  viscoelastic rod, plug ejection, barrier, cumulative jet, space debris, destruction, longitudinal oscillations, shock wave
Page:  452

MODELING AERODYNAMIC CHARACTERISTICS OF A WIND ENERGY INSTALLATION WITH ROTATING CYLINDER BLADES ON THE BASIS OF THE ANSYS SUITE

Modeling has been carried out for the aerodynamics of air fl ow past the windwheel with three cylinder blades rotating around their axis using the Ansys suite. A system of equations in approximation of a realizable k–ε turbulence model was solved by the method of fi nite volumes using the approach of multiple (imbeddable) systems of coordinates. Patterns have been constructed for vortex zones near cylinder blades. Analysis is given of the aerodynamic characteristics of fl ow past rotating cylinders under the conditions of the operation of a wind turbine using the Magnus eff ect depending on the velocity of cylinders′ rotation and the Reynolds number. Dependences have been obtained for the drag force of the windwheel, the lift force of the cylinder, and also the force moment on the velocity of approach fl ow  
Author:  N. K. Tanasheva , A. R. Bakhtybekova , K. M. Shaimerdenova , S. E. Sakipova , N. N. Shuyushbayeva
Keywords:  windwheel, rotating cylinder blades, aerodynamics, drag force, lift force, Magnus eff ect, modeling, ANSYS.
Page:  457

ON CALCULATION OF FLOWS OF HETEROGENEOUS MEDIA BY THE MULTIDIMENSIONAL NODAL METHOD OF CHARACTERISTICS

A description is given of a nodal method of characteristics, designed for integrating hyperbolic systems, based on splitting the initial system of equations into a number of one-dimensional subsystems, with the one-dimensional nodal method of characteristics being used for their calculation. The calculating formulas of the method are cited. A number of fl at and three-dimensional test problems have been calculated using this method. The results of calculations have been compared with the existing self-similar solutions  
Author:  V. S. Surov
Keywords:  heterogeneous media, multidimensional nodal method of characteristics
Page:  464

MODELING THE CAPILLARY INFLOW OF A LIQUID TO DRY SPOTS ABOVE VAPOR BUBBLES AS A FACTOR OF INCREASING THE CRITICAL HEAT-FLUX DENSITY DURING THE BOILING ON A POROUS SURFACE

The authors propose a calculation model for the process of infl ow of a liquid from a microfi lm to dry spots above vapor bubbles, which occurs in nucleate boiling and is due to the action of capillary forces (Laplace head) in a porous coating on the heating surface. In comparing the value of the heat fl ux from the heating surface to the interface in the zone of intense evaporation of the liquid and the value of the heat fl ux to evaporate the liquid sucked through a porous substrate to a dry spot, it turns out that these values are comparable, which explains the effect of rise in the critical density of the heat fl ux on porous surfaces compared to "smooth" surfaces. A comparison of the results of quantifi cation of this effect with the proposed model and the experimental data obtained during the boiling of water on a porous surface that was formed by nanoparticles precipitated from a nanolfl uid has shown their mutual agreement  
Author:  E. D. Fedorovich , A. N. Kovalenko , S. S. Makukhin
Keywords:  nucleate boiling, active nucleation site, vapor bubble, microfi lm, dry spot, critical heat-fl ux density, porous coating, capillary-infl ow effect
Page:  473

STRUCTURAL INHOMOGENEITY AND EFFECTS OF SEPARATION BY SIZE AND DENSITY IN GRAVITY FLOW OF GRANULAR MATERIALS

The authors have substantiated the expediency of representing the effect of separation of particles as a result of the conjugation of phenomena that are caused by the inhomogeneity of a granular medium and the spatial structural heterogeneity of a shear fl ow. With the general separation-dynamics model taking account of separation, convection, and mixing fl ows, regions of relative values of particle size and density have been determined, in which the dominance of the separation fl ows due to the local and spatial inhomogeneity of the granular-medium's rapid gravity fl ow is noted. It has been established that the boundary of the regions of dominance of separation fl ows with a fundamentally different physical nature which is determined by hydrodynamics and diffusion kinetics is near the equilibrium line of inhomogeneous-particle masses.  
Author:  V. N. Dolgunin, A. N. Kudi, A. G. Tarakanov
Keywords:  granular material, rapid gravity fl ow, structural inhomogeneity, separation by size and density, segregation, migration, quasi-diffusion
Page:  484

ESTIMATION OF THE PARAMETERS OF THE POROUS STRUCTURE OF POWDER MATERIALS

Based on the globular model with the use of the values of porosity and particle size, a method is presented for calculating the structure parameters of porous monofractional powder composite materials for fi lters. A formula for determining the average (hydraulic) radius of the capillaries of permeable materials has been obtained, which is more accurate than the Kozeny formula. The results of calculating the average radius of capillaries and of the permeability of porous powder materials by the proposed dependences are presented, which are in better agreement with experimental data than calculations by the Kozeny formula  
Author:  Yu. N. Kryuchkov
Keywords:  model, fi lter, structure, coordination number, average radius of capillaries, packing density, porosity, particle size, specifi c surface, coeffi cient of capillary tortuosity, permeability
Page:  495

SIMULATION OF HYDRAULIC DIFFUSION PROCESSES AND FILTRATION OF OIL IN A POROUS BED

The problems of analysis and solution of the equation of hydraulic diffusion for the oil bed as an isotropic porous medium with different boundary conditions are considered. A collection of analytical solutions and the possibilities of using them to construct a pressure recovery curve for estimating the coeffi cients of hydraulic diffusion and permeability of the bed are given. The one-dimensional solutions of these equations are compared with experimental data obtained on an operating setup, and their satisfactory convergence is demonstrated. The solutions obtained can be used to solve various problems of oil fi ltration in an isotropic porous medium. The structure formation of the non-Newtonian oil due to asphalt-resinous substances and their infl uence on the fi ltration rate of oil and its rheological properties have been investigated. New rheological equations for non-Newtonian oil fi ltration in a porous medium have been suggested  
Author:  G. I. Kelbaliev , S. R. Rasulov , D. B. Tagiev
Keywords:  oil, hydraulic diffusion, fi ltration, porous medium, permeability, viscosity, rheology, structure formation, shear stress
Page:  499

HYBRID LBGK-FD MODEL FOR STUDYING TURBULENT NATURAL CONVECTION

A hybrid mesomacroscopic approach has been developed for modeling developed turbulent thermogravitational fl ows in closed rectangular differentially heated regions. Within the framework of the formulated approach, it is proposed to use the mesoscopic lattice Boltzmann equations to describe gas-dynamical processes, and the macroscopic energy equation solved by the fi nite difference method for thermodynamic ones. To approximate the Boltzmann equation, simultaneous relaxation and a two-dimensional nine-speed scheme were used. Mathematical simulation was carried out at the Rayleigh number Ra = 1010 and the Prandtl number Pr = 0.71. The infl uence of the order of approximation of the energy equation on the local heat transfer characteristics has been analyzed. It is found that an increase in the number of computational nodes leads to the smoothing of pulsations in the fl ow. In this case, the results of numerical simulation agree satisfactorily with the "reference" data obtained by other researchers.  
Author:  A. É. Nee
Keywords:  turbulence, hybrid method of lattice Boltzmann equations, method of fi nite differences, natural convection
Page:  508

NUMERICAL SIMULATION OF A FORCED CONVECTION LAMINAR FLUID FLOW WITH REGARD FOR THE THERMODIFFUSION OF NANOPARTICLES IN IT

The forced convection of the nanofl uid representing a water with aluminum oxide particles, fl owing in the laminar regime in a circular channel with a heat fl ow of constant density at the channel wall, was numerically investigated by the homogeneous and heterogeneous models of the fl uid fl ow with regard for the transport of nanoparticles in it due to their diffusion or thermodiffusion. An increase in the thermodiffusion of nanoparticles in a laminar fl uid fl ow with increase in their concentration in it was demonstrated. The results of calculations performed by the indicated two models are in good agreement with the corresponding experimental data. However, the homogeneous model as a whole approximates experimental data more closely. It is shown that, in the case where the concentration of nanoparticles in a fl uid is high (6%), the infl uence of their thermal diffusion on the heat transfer and the pressure drop in the laminar fl uid fl ow in a channel does not exceed 2%  
Author:  D. V. Guzei , A. V. Minakov , V. Ya. Rudyak
Keywords:  forced convection, numerical simulation, nanofl uid, thermal diffusion, two-component model, experiment
Page:  516

REFRACTIVE AND ELECTROPHYSICAL PROPERTIES OF DISPERSED SOLUTIONS OF FULLERENE C60 IN BINARY SOLVENTS

An experimental study has been made of the infl uence of the concentration of a solvent and a solute on the clusterization of fullerene C60 molecules in a C60/xylol/hexane solution by refractometry methods. By the methods of dynamic light scattering and transmission electron microscopy, it has been established that when a nonequilibrium method of preparation of a fullerene C60 solution in binary mixtures (xylol + hexane) is employed negatively charged clusters of diameters ~60–70 nm are formed in the solution. It has been established that the high aggregative stability of the solution of fullerene with a concentration of C60 of ~0.036 g/L is determined by the relatively high values of the electrokinetic ζ potential of nanoclusters (ζ = –26.6–28.2 mV).  
Author:  U. K. Makhmanov
Keywords:  fullerene C60, mixtures of solvents, refractive index, electrokinetic potential, microscopy
Page:  527

PREPARATION OF HYBRID NANOFLUIDS, THEIR THERMOPHYSICAL PROPERTIES, AND STABILITY PARAMETERS

A review of methods of preparation of hybrid nanofl uids produced with the use of particles of metals, nonmetals, and
their oxides as well as results of recent investigations on the thermophysical properties of these nanofl uids and their
stability are presented.  
Author:  Okafor Anthony Amaechi , Mgbemena Chinedum Ogonna
Keywords:  hybrid nanofl uid, preparation, characterization, properties, stability
Page:  533

THERMODYNAMIC PROPERTIES OF A LIQUID MIXTURE OF CYCLOHEXANE WITH DECALIN AT TEMPERATURES 298.15–433.15 K AND PRESSURES UP TO 100 MPa

An experimental study of the density and speed of sound for a liquid mixture of decalin with cyclohexane in the range of temperatures 298.15–433.15 K and pressures up to 100 MPa has been carried out. The parameters of the Redlich– Kister equations for an excess volume in a wide range of temperatures and pressures and for excess isobaric heat capacity at atmospheric pressure have been obtained. The values of density, speed of sound, isobaric and isochoric heat capacities, isobaric expansion coeffi cient, isotropic and isothermal compressibility coeffi cients, as well as of the corresponding excess properties in the range of temperatures 298.15–433.15 K and pressures 0.1–100.1 MPa have been calculated.  
Author:  A. P. Shchemelev , V. S. Samuilov , N. V. Golubeva , O. G. Poddubskii
Keywords:  decalin, cyclohexane, mixture, density, speed of sound, thermodynamic properties
Page:  539

INFLUENCE OF THE CONDUCTIVITY OF RESONATOR WALLS ON THE CHARACTERISTICS OF A MICROWAVE GENERATOR WITH A VIRTUAL CATHODE: NUMERICAL EXPERIMENTS

Using PIC simulation, the authors have carried out an investigation into the generation characteristics of a microwave generator with a virtual cathode as functions of the conductivity of the material of resonator walls. The dependence of the peak power of microwave generation in the resonator on the value of conductivity has been obtained which shows a decrease in the power with conductivity. No substantial change in the generation spectrum with variation of the conductivity has been found.  
Author:  A. E. Dubinov , V. P. Tarakanov
Keywords:  microwave generator with a virtual cathode, resonator, conductivity
Page:  553

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