HEAT AND MASS TRANSFER IN DISPERSED AND POROUS MEDIA
IMPROVING THE PERFORMANCE OF AN ADSORPTION HEAT CONVERTER IN CONDENSATION AND EVAPORATION OF THE ADSORBATE IN SORBENT PORES
M. Yu. Lyakh, O. S. Rabinovich, L. L. Vasiliev, and A. P. Tsitovich
The possibilities of raising the specifi c refrigerating capacity and the cooling temperature of an adsorption refrigerator through the phase transition of the adsorbate in low-temperature-sorbent pores have been investigated by the computer-modeling method. Using an adsorption refrigerator with busofi te-based MnCl2 and BaCl2 sorbents (in the high-temperature and low-temperature adsorbers respectively) as an example, it has been shown that the operating regime of the refrigerator with adsorbate condensation and evaporation enables one to raise the specifi c capacity of the apparatus by 20% and to double the average cooling temperature.
Keywords: adsorption heat converter, adsorption, capillary condensation, composite sorbent.
ON THE EFFICIENCY OF USING THERMOCOMPRESSORS IN THE PROCESSES OF DRYING AND HEAT TREATMENT OF MATERIALS AND A METHOD FOR CALCULATING THEM
P. V. Akulich
We present a method for calculating the process of drying materials with the use of a thermocompressor and recirculation (bypassing) of a part of the drying agent. The results of the calculations performed show that when of using a thermocompressor in the drier, the effi ciency of the latter increases.
Keywords: thermocompressor, drying, heat treatment.
SEDIMENTATION OF A STOKESIAN MONODISPERSE LARGE PARTICLE SUSPENSION IN A STIRRED LAYER WITH A MOVING FREE BOUNDARY
A. V. Ryazhskikh,a A. A. Boger,b M. I. Slyusarev
and V. I. Ryazhskikha
Based on diffusion concepts, the problem of deposition of monodisperse large Stokesian particles in a stirred plane layer with a vertically moving free boundary has been formulated and solved.
Keywords: sedimentation, monodisperse Stokesian particles, moving free boundary, plane layer.
QUALITATIVE ANALYSIS AND NUMERICAL SIMULATION OF THE MOVEMENT OF A PARTICLE IN A CHANNEL HAVING PERMEABLE WALLS WITH ACCOUNT FOR THE ACTION OF MASS FORCES
K. N. Volkov
The movement of a particle in a round channel with permeable walls was investigated with account for the action of the mass forces on it. The results of a qualitative analysis and a numerical simulation of the trajectories of movement of this particle were compared. The singular points of the trajectory of movement of the indicated particle at characteristic parameters of the problem changing in wide ranges were determined and the regimes of this movement were classifi ed depending on the Stokes and Froude numbers.
Keywords: injection, channel, particle, qualitative analysis, numerical simulation, singular point.
THERMAL REGIME OF A CAP-TYPE GAS DISTRIBUTOR WITH ACTIVE THERMAL INSULATION
Yu. S. Teplitskii,a E. A. Pitsukha,b V. A. Borodulya,a and V. L. Malevicha
The thermal state of a cap-type gas distributor with active thermal insulation in the form of a ventilated granular bed is modeled. The temperatures of air at exit from the granular bed and of the upper gas-tight plate of the gas distributor have been calculated by the method of successive approximations. The effi ciency of active thermal insulation that substantially reduces the gas distributor temperature and simultaneously serves as a preheater for the primary air entering into the high-temperature fl uidized bed is shown.
Keywords: high-temperature fl uidized bed, fl uidized-bed furnace, gas distributor, active thermal insulation, granular bed, heat-transfer model, cap.
ACTIVE THERMAL INSULATION WITH CIRCULAR BLOWING OF A HEAT CARRIER AT HIGH PECLET NUMBERS
Yu. S. Teplitskii,a E. A. Pitsukha,b V. A. Borodulya and V. L. Malevicha
We have studied the thermal regime of a granular bed circularly blown by a heat carrier. The effi ciency of such a system used as an active thermal insulation of combustion equipment surfaces is shown.
Keywords: ring-shaped granular bed, active thermal insulation, heat carrier fi ltration, furnace, heat transfer, Peclet number.
EXPERIMENTAL INVESTIGATION OF THE DISPERSION OF LIQUIDS BY EJECTION ATOMIZERS
V. A. Arkhipov, S. S. Bondarchuk, M. Ya. Evsevleev, I. K. Zharova,a A. S. Zhukov, S. V. Zmanovskii,d E. A. Kozlov, A. I. Konovalenko,a and V. F. Trofimov
This paper presents the results of an experimental investigation of the dispersivity of liquid droplets in the spray cone of ejection atomizers. The calculational droplet size distribution function was measured by the method of low angles of the probe laser radiation scattering indicatrix on a pneumohydraulic bench under cold blow conditions. The effi ciency of the proposed circuit designs of atomizers has been analyzed.
Keywords: liquid atomization, ejection atomizer, spray cone, dispersivity of droplets, pneumohydraulic bench, method of low angles of the scattering indicatrix, droplet size distribution function.
COMPUTER SIMULATION OF POROUS LAYERS BASED ON THE METHOD OF DISCRETE ELEMENTS
E. N. D’yachenkoa and J. G. Dueckb
We propose a numerical suspension sedimentation and fi ltration model based on the dynamic variant of the method of discrete elements. The model refl ects the behavior of particles at the micro- and mesolevels (formation of pores, arches, and fl akes) and qualitatively reproduces macroeffects: sedimentation of a layer of particles and slow processes of the shrinkage of this layer, as well as its compaction under the gravity of particles and of an externally applied force.
Keywords: sedimentation layer formation, fi ltration layer consolidation, discrete elements method.
MHD FLOW OF A ROTATING FLUID PAST A VERTICAL POROUS FLAT PLATE IN THE PRESENCE OF CHEMICAL REACTION AND RADIATION
S. Sivaiah UDC 536.25
The MHD fl ow of a rotating fl uid past a vertical porous fl at plate in the presence of chemical reaction and radiation is studied. The chemical reaction is assumed to be of the fi rst order. The dimensionless governing equations are solved numerically using the fi nite element method. The effects of various physical parameters on the complex velocity, temperature, and concentration fi elds across the boundary layer are investigated. It is observed that the concentration decreases with increase in the chemical reaction parameter and the temperature increases with the radiation parameter.
Keywords: MHD, chemical reaction, radiation, fi nite element method.
HEAT CONDUCTION AND HEAT TRANSFER IN TECHNOLOGICAL PROCESSES
LOW-INERTIA METHOD OF MEASUREMENT OF RADIANT FLUXES UNDER VACUUM CONDITIONS
S. O. Marach and A. I. Shnip
A low-inertia method of measurement of incident radiant heat fl uxes in vacuum, in particular, in thermovacuum testing of space equipment in a pressure chamber, has been proposed. Mathematical modeling of the process of measurement has been performed for a device implementing this method. Modeling results have shown the high operating characteristics of this method.
Keywords: radiant heat fl uxes, mathematical modeling, thermovacuum testing of spacecraft.
ASYMPTOTIC ANALYSIS OF SOLUTION OF A NONLINEAR PROBLEM OF NONSTATIONARY HEAT CONDUCTION OF LAMELLAR ANISOTROPIC INHOMOGENEOUS SHELLS WITH MIXED BOUNDARY CONDITIONS ON FACES
A. P. Yankovskii
An external asymptotic expansion of the solution of a nonlinear problem of nonstationary heat conduction of lamellar anisotropic inhomogeneous shells and plates with mixed boundary conditions on faces has been constructed with account of the thermal response of the layers? materials. The resulting two-dimensional resolvents have been analyzed, and the asymptotic properties of solutions of the heat-conduction problem have been investigated. A physical explanation has been provided for certain features of the asymptotic expansion of temperature.
Keywords: heat conduction, thermal response, asymptotic analysis, lamellar shells, anisotropy and inhomogeneity.
SIMULATION OF THE HEAT ACCUMULATION AND EXTRACTION PROCESSES IN THE HEAT EXCHANGER–GROUND SYSTEM
B. I. Basok, T. G. Belyaeva, L. N. Kuzhel and M. A. Khibina
We present the results of the computational modeling of the dynamics of the processes of heat accumulation and extraction in the ground mass by a vertical single heat exchanger with the use of the PHOENICS modeling program package. The results of the calculations have been compared with analytical-calculation models. Good agreement between the obtained data has been obtained.
Keywords: season accumulation of heat, computational modeling, heat exchange, ground well vertical heat exchanger.
HEAT TRANSFER THROUGH MULTILAYER WINDOW MULTIPLE GLASS UNITS WITH ACCOUNT FOR THE ACTION OF SOLAR RADIATION
A. I. Nakorchevskii and A. N. Nedbailo UDC 536.2+662.997
A method to calculate heat losses through window multiple glass units with consideration for climatic factors and the thermal effect of the sun is suggested. An example of the method?s numerical realization is given.
Keywords: wind, enclosure, solar radiation, multiple glass unit, temperature, heat fl ux, heat transfer.
MODELING OF THE LIGHT SPECKLE FIELD STRUCTURE INSIDE A MULTILAYER HUMAN SKIN TISSUE
UDC 535.36, 535.41
V. V. Barun,a,b S. K. Dik,a A. P. Ivanov,b and N. D. Abramovicha
We present an analytic method and the results of investigating the characteristics of the interference pattern formed by multiply scattered light in a multilayer biological tissue of the type of human skin at the wavelengths of the visible and neat IR spectral regions under laser irradiation. Calculations were performed with the use of the known solutions of the equations of radiation transfer in the biotissue and the relation between the theory of propagation of light in a scattering medium and the coherence theory. The radial structure of the light fi eld in the depth of the human skin formed by coherent and incoherent radiation depending on its biophysical parameters has been investigated. The characteristic sizes of speckles in each layer of the skin have been estimated. The biophysical factors connected with the volume concentration of blood in the dermis and the degree of its oxygenation infl uencing the contrast of the speckle pattern in the dermis have been discussed. The possibility of formulating and solving inverse problems of biomedical optics on the restoration of blood parameters from measurements of speckle characteristics has been shown.
Keywords: speckle pattern, biological tissue, human skin, radiation transfer theory, coherent light, radiation absorption, multiple scattering of radiation, blood, melanin.
COMPUTATIONAL-EXPERIMENTAL DETERMINATION OF WALL TEMPERATURE VARIATION IN THE FORCED MOTION OF AIR INSIDE A CIRCULAR PIPE
N. P. Starostin and M. A. Vasil'eva
We suggest an approach to calculating the change in pipe wall temperature allowing one to evaluate the duration of preheating polyethylene pipes in a coil by a heated air for carrying out installation and placement works in the construction of gas pipes under low-temperature conditions. An example of the computational–experimental determination of the duration of preheating a polyethylene pipe in the range of the ambient air temperatures is given.
Keywords: polyethylene pipe, temperature, heated air, calculation, duration of heating.
HEAT AND MASS TRANSFER IN COMBUSTION PROCESSES A CONTRIBUTION TO THE PROBLEM OF INITIATION OF A COMBUSTION SOURCE IN AN OIL-SATURATED BED
I. A. Koznacheev and K. V. Dobrego
The problem on in-situ self-ignition of an oil-saturated bed under the conditions of forced fi ltration of an oxygencontaining gas has been solved with analytical and numerical methods with account of the burnout of a defi cient gas component. The infl uence of the burnout of this component and of convective removal of heat from the bed on the time of its self-ignition has been determined. Recommendations for the optimum regime of initiation of the self-ignition of the bed with account of variation of the blast fl ow rate and the oxygen content have been given.
Keywords: thermal explosion, self-ignition, fi ltration, in-situ combustion.
CONVERSION OF METHANE TO HYDROGEN IN A REVERSIBLE FLOW REACTOR IN THE PROCESS OF FILTRATION COMBUSTION OF FUEL MIXTURES ENRICHED WITH OXYGEN
Yu. M. Dmitrenko and R. A. Klyovan
This paper considers the process of partial oxidation of methane to syngas in a reversible fl ow reactor in the process of fi ltration combustion of fuel mixtures enriched with oxygen in an inert porous medium. Experimental studies have been made of the infl uence of the volume concentration of oxygen in the initial fuel mixture on the basic parameters of the conversion process — the maximum temperature in the combustion wave and the composition of reaction products. Investigations have been carried out for fuel mixtures having different calorifi c values under the same fi ltration conditions. It has been shown that the addition of oxygen to the initial methane–air mixture permits increasing considerably the effi ciency of the conversion process.
Keywords: conversion of methane, syngas, partial oxidation reaction, superadiabatic effect, fi ltration combustion wave, inert porous packed bed, reversible fl ow reactor.
MODELING OF EXPLOSION GAS DYNAMICS WITH ACCOUNT OF DETONATION
D. O. Morozov UDC 532.5:539.5
The physical and hydrodynamic processes in the initial phase of explosion of condensed explosives in the air have been considered. The role of the processes of energy release connected with the explosive detonation has been analyzed. The equations of formal kinetics for modeling the processes of transformation of the original substance into detonation products have been described. The results obtained with the use of the equation of state of an ideal gas with a constant adiabatic index have been compared with calculations, where for the equation of state widerange tables of properties of the air and explosion products were used. The stage of detonation of an explosive is included in the self-consistent hydrodynamic model used for describing the explosion processes from the moment of initiation of the detonation wave to the moment the air shock wave is formed, as well as in describing its propagation and
Keywords: explosion, shock wave, detonation.
EXPERIMENTAL STUDY OF THE CHANGE IN THE MASS OF WATER DROPLETS IN THEIR MOTION THROUGH HIGH-TEMPERATURE COMBUSTION PRODUCTS
R. S. Volkov, O. V. Vysokomornaya, UDC 536.4 G. V. Kuznestov, and P. A. Strizhak
An experimental study of the integral characteristics of evaporation of single water droplets in their motion through high-temperature combustion products has been carried out with a setup incorporating a high-speed measuring PIV system. The characteristic rates of change in the mass of the water droplets during passage through a fl ame of fi xed height have been determined. Numerical evaluation of the evaporated liquid mass has been performed.
Keywords: evaporation, heat and mass transfer, combustion products, water droplet, fi nely pulverized water.
PYROLYSIS OF COMPOSITIONS OF MIXTURES OF COMBUSTIBLE SHALES AND BROWN COALS DEPOSITED IN BELARUS
I. I. Lishtvan, V. M. Dudarchik, V. M. Kraiko, and Yu. V. Belova
This paper presents the results of investigating the pyrolysis of compositions of mixtures of brown coals and combustible shales in a close-packed and a moving layer and the yield dynamics of the pyrolysis gas and resin. A comparative analysis of the quality of pyrolysis products obtained from combustible shales and brown coal and from their mixtures has been performed.
Keywords: combustible shales, brown coals, mixture compositions, pyrolysis, pyrolysis gas, resin.
INFLUENCE OF SEPARATION OF AIR DISSOLVED IN FUEL ON THE RATE OF ITS GRAVITY FLOW IN A PIPELINE AT AN UNDERPRESSURE
E. L. Kitanin,a E. E. Kitanina,a V. L. Zherebtsov O. A. Merkulov,b* M. M. Peganova,b S. G. Stepanov,b D. A. Bondarenko,c and D. Morrisond
Results of experimental investigations of the infl uence of the separation of the air dissolved in a fuel on the regime of fl ow of this fuel in a pipeline at an underpressure are presented. It is shown that, when the pressure in the pipeline decreases, beginning with any its value, the fl ow rate of the fuel in the pipeline decreases sharply as a result of the separation of air from it and the formation of the two-phase fuel–air fl ow. It has been established that the pressure at which active separation of the air dissolved in the fuel begins depends on the temperature of the fuel and the velocity of its fl ow in the pipeline.
Keywords: experiment, air separation, chromatograph, aviation fuel, underpressure, two-phase fuel fl ow, gas concentration, fuel fl ow rate.
HYDROGASDYNAMICS IN TECHNOLOGICAL PROCESSES
ANALYSIS OF THE INFLUENCE OF THE TEMPERATURE FACTOR ON THE INTENSIFICATION OF THE HEAT EXCHANGE IN A LANE BANK OF ROUND TUBES IN THE CASE OF LAMINAR OIL FLOW ABOUT IT
S. A. Isaev,a P. A. Baranov,b Yu. V. Zhukova,c and A. E. Usachovd
The results of a numerical simulation of the convective heat exchange in a lane bank of round tubes in the case of laminar fl ow of an oil about it are presented. The Navier–Stokes and energy equations were solved using the multiblock computational technologies realized in the VP2/3 package. It is shown that, in the case of laminar M20- oil fl ow about a round-tube bank (of size 2 ? 1), the convective heat transfer in it is ten times larger than in the case of air fl ow about this bank and that the velocity of the separation fl ow increases by two times with increase in the temperature of the tube wall from 20 to 40oC.
Keywords: convective heat exchange, separation fl ow, laminar fl ow, bank of round tubes, oil, simulation, procedure of pressure correction, periodic boundary conditions, Rhie–Chow approach, multiblock computational technologies, VP2/3 package.
SIMULATION OF A FLUID FLOW IN A CHANNEL WITH A MOVING SIDE SURFACE AND INJECTION
K. N. Volkov
A numerical simulation of the nonviscous- and viscous-fl uid fl ows in the channel of a solid-fuel charge with moving permeable walls and injection has been carried out with the use of the k–? model of turbulence. Calculation results obtained within the framework of different approaches to the description of the fl uid-fl ow fi eld in a channel were compared.
Keywords: injection, channel, nonstationarity, simulation.
TOWARD THE THEORY OF THE HYDRODYNAMIC INJECTOR
S. K. Betyaev
The scheme of an ideal fl uid fl ow in a plane or a circular injector through the side surface of which a working fl uid is injected is discussed. A one-dimensional theory is proposed. The characteristic feature of this fl ow at the line where the blowing of the fl uid begins has been investigated. It has been established that this line is responsible for the formation of the velocity contact discontinuity in the corner region at whose boundaries the working fl uid is injected.
Keywords: injector, bubble, ejector, channel, ideal fl uid fl ow, contact discontinuity.
INFLUENCE OF THERMAL PARAMETERS ON THE STRUCTURE AND INTENSITY OF VORTEX MOTION OF A MELT IN DC ARC FURNACES
O. V. Kazak
The vortex motion of a metal melt in a dc bottom-electrode arc furnace has been modeled numerically with allowance for different thermal parameters. The motion of the melt was described by magnetic hydrodynamic equations for a nonisothermal liquid. An algorithm of solution of the problem within the framework of standard packages of applied programs has been developed. It has been shown that a determining contribution to the vortex motion of the metal melt is made by the electromagnetic Lorentz force. It has been established that a signifi cant infl uence is exerted by convective fl ows resulting from the nonuniform distribution of heat that is released in the electric-arc region. A nonuniform distribution of the Joule heat from the electric current fl owing over the melt exerts a minor infl uence on the structure and intensity of the vortex melt motion.
Keywords: dc arc furnaces, numerical modeling, vortex motion of a metal melt, Lorentz force, convective flows.
NANOSTRUCTURES SCALE INVARIANCE OF NANOSIZE STRUCTURES ARISING FROM THE OVERLAP OF SINGLE ION TRACKS
A. B. Demchishin,a P. A. Selishchev,b and B. I. Basokc
Nanosize structures that may arise from the multiple overlapping of single tracks with growth in the irradiation dose have been modeled without account of the process of formation of the single tracks themselves. It has been established that the percolation cluster of the structure of overlapped ion tracks is a physical fractal. The surface area of such a cluster nonmonotonically depends on the angle of irradiation with fast heavy ions. It has been determined that the percolation irradiation dose depends on the dimension of the sample by a power law. The power of this dependence is inversely proportional to the critical exponent which is determined by the track shape and by the distribution of the tracks over the sample’s depth.
Keywords: track, branching structures, fast heavy ions, critical exponents, percolation threshold, scaling hypothesis.
TRANSFER PROCESSES IN LOW-TEMPERATURE PLASMA
SHORT-WAVE CHARGE INSTABILITIES OF WEAKLY IONIZED PLASMA FLOWS
E. N. Perevoznikov
Conditions for excitation of high-frequency charge instabilities in a weakly ionized gas plasma fl ow in the approximation of high velocities of motion of its components and large disturbance gradients are considered.
Keywords: weakly ionized gas plasma fl ow, high-frequency charge instabilities, high velocities of motion of plasma components, disturbance gradients.
RADIATION RESISTANCE OF STRUCTURAL MATERIALS OF NUCLEAR REACTORS ON IRRADIATION WITH HIGH-ENERGY HYDROGEN AND HELIUM IONS
F. F. Komarov, A. F. Komarov, Vl. V. Pil'ko, and V. V. Pil'ko
Basic principles of determination of the radiation resistance of structural materials of nuclear reactors with implantation of high-energy hydrogen and helium atoms have been presented. The parameters of the process of implantation of light irons have been calculated. By scanning-electron-microscopy, optical-microscopy, and interference methods, the authors have studied the surface structure of samples of steel-3, stainless steel, and D16 alloy immediately after irradiating them with hydrogen and helium atoms with an energy of 200 to 400 keV in the range of doses from 1016 to 3·1017 ions/cm2 and after annealing these samples thermally at temperatures from 300 to 550oC. Threshold blistering doses for all the studied materials and annealing temperatures for visualizing structural defects have been determined.
Keywords: nuclear reactor, structural materials, high-energy ions, radiation resistance, ion implantation.
PARAMETRIC OSCILLATIONS OF A STIFFENED CYLINDRICAL SHELL WITH ACCOUNT OF ITS DAMAGEABILITY AND OF EXTERNAL EFFECTS EXERTED ON IT
F. S. Latifov, M. O. Yusifov, and F. A. Seifullaev
The problem on parametric oscillations of a longitudinally stiffened cylindrical shell of circular cross section fi lled with viscoelastic medium has been solved with the variational principle.
Keywords: oscillation frequency and damageability of the shell, longitudinal rod, viscosity, critical force.
HEAT AND MASS TRANSFER IN THE OVER-SHOWER ZONE OF A COOLING TOWER WITH FLOW ROTATION
M. M. Hemmasian Kashania and K. V. Dobregob
The influence of fl ow rotation in the over-shower zone of a natural draft wet cooling tower (NDCT) on heat and mass transfer in this zone is investigated numerically. The 3D geometry of an actual NDCT and three models of the induced rotation velocity fi elds are utilized for calculations. Two phases (liquid and gaseous) and three components are taken into consideration. The interphase heat exchange, heat transfer to the walls, condensation–evaporation intensity fi eld, and other parameters are investigated as functions of the induced rotation intensity (the inclination of the velocity vector at the periphery). It is shown that the induced fl ow rotation intensifi es the heat and mass transfer in the over-shower zone of an NDCT. Flow rotation leads to specifi c redistribution of evaporation–condensation areas in an NDCT and stimulates water condensation near its walls.
Keywords: cooling tower, over-shower zone, heat and mass transfer, numerical simulation.