HEAT AND MASS TRANSFER IN COMBUSTION PROCESSES TALBOT METHOD OF INVESTIGATION OF THE CONCENTRATION DISTRIBUTION OF METHANE IN A TURBULENT AXISYMMETRIC JET
P. P. Khramtsov, O. G. Penyazkov, I. N. Shatan and I. A. Shikh
UDC 533.9.082.5; 537.523.2
The results of calculating the averaged concentration of methane in the fl ow fi eld of a turbulent axisymmetric jet on the basis of experimental data obtained by the Talbot method have been given.
Keywords: Talbot effect, turbulent jet, refractive index.
ROLE OF HEAT TRANSFER IN THE STABILIZATION OF THE FLAME IN A CLOSED VOLUME FILLED WITH HIGH-POROSITY MEDIUM
K. V. Dobrego, I. M. Kozlov, N. N. Gnezdilov, and E. S. Shmelev
The results of modeling of the combustion of a gas-air mixture in a closed volume fi lled with high-porosity medium have been given. A comparison of the calculation results to experimental data has shown their qualitative agreement.
It has been established that a quasistationary regime of propagation of the fl ame is possible in the case of fairly large relative length of the system and specifi c surface of the porous medium. Rapid deceleration of the fl ame is attributed
to the decrease in the area of its surface because of the quenching on the reactor walls and the intense heat exchange between the hot combustion products and the porous medium. Stabilization of the fl ame propagation occurs when the heat release in gaseous combustion and the heat loss during the heat exchange between the combustion products and the porous medium are approximately equal.
Keywords: porous medium, numerical modeling, stabilization of the fl ame, fl ame dynamics
PARAMETERS OF HEAT EXCHANGE AND COMPRESSION IN THE COMBUSTION OF POWDER CHARGES UNDER A WATER LAYER
G. V. Melik-Gaikazov
The mechanisms of change in the pressure in an oil well in the process of combustion of a powder charge positioned at its bottom were investigated. A model of calculating the working process in a well by the heat exchange of it with the environment and the compressibility of the liquid in the well is proposed. It is shown that about one third of the energy of the powder is expended for the displacement of the liquid from the well. It has been established that the dependence of the maximum pressure in an oil well on the mass of a powder charge is common in character for charges of different types. The dynamic heads of a liquid in a well in the liquid-compression phase and in the phase of reciprocating movement of the liquid after the termination of the combustion of a powder charge were calculated.
Keywords: oil well, powder charge, charge mass, dynamic head and compressibility of a liquid.
HEAT AND MASS TRANSFER IN DISPERSED AND POROUS MEDIA
MODEL CHANNEL FOR ANALYZING THE FLOW AND HEAT EXCHANGE OF ONE- AND TWO-PHASE MEDIA IN A BALL PACKED BED
O. N. Kaban’kov, L. A. Sukomel, and V. V. Yagov
With the use of computational modeling a search has been made for a confi guration of a rectilinear channel, in which the fl ow in a layer from spherical particles could be best simulated.
Keywords: rectilinear channel, clearance of the ball packed bed, porous medium, binomial law of fi ltration.
CHARACTERISTICS OF ACTIVE THERMAL INSULATION BASED ON INFILTRATED GRANULAR BED
Yu. A. Teplitskii, V. L. Malevich, and D. G. Belonovich
A criterion of active thermal insulation has been introduced and using it, a method for estimating the thermal insulation properties of a ring-shaped granular bed with longitudinal blowing of a heat carrier has been substantiated.
A practical method of calculating this type of insulation has been developed.
Keywords: ring-shaped granular bed, thermomechanics, heat carrier, particle diameter, heat-exchanger model, active thermal insulation criterion.
EXPERIMENTAL STUDY OF A THREE-ADSORBER SORPTION REFRIGERATOR FOR UTILIZATION OF RENEWABLE SOURCES OF ENERGY
A three-adsorber refrigerator has been created and experimentally tested, in which use is made of a composite sorbent consisting of activated carbon fi ber and alkali salts. This sorbent has a high capacity of storage of refrigeration characteristic of chemical coolers and a high sorption rate characteristic of adsorption refrigerators. The sorbent structure makes it possible to effect a convective intrapore process of cooling of the sorbent through intense twophase
heat transfer. A three-adsorber refrigerator has a higher refrigeration effi ciency and smaller mass and overall dimensions than a traditional two-stage four-adsorber refrigerator.
Keywords: adsorption, chemical reactions, heat pipes, renewable sources of energy.
DETERMINATION OF THE FLUIDIZATION REGIMES OF BICOMPONENT BEDS
OF SOLID PARTICLES AND THE CHARACTERISTIC VELOCITIES OF A GAS IN THESE BEDS BY THE PULSATIONS OF THE DIFFERENTIAL PRESSURE IN THEM
D. M. Viryasov, R. L. Is’emin, S. N. Kuz’min, N. B. Kondukov, and A. V. Mikhalev
The possibility of determining the regime of fl uidization of a bicomponent bed by the dependences of the statistical characteristics of the pulsations of the different pressure in this bed on the velocity of the gas blown through it is demonstrated. An algorithm of estimating the characteristic gas velocities corresponding to the transformation of the bed into the regimes of fl uidization and turbulent fl uidization at room temperature and at much higher temperatures has been developed. This algorithm allows one to determine the indicated velocities more exactly, as compared to the traditional methods, by the dependence of the differential pressure in the bed on the velocity of the gas blown through it.
Keywords: fluidized bicomponent bed, fl uidization velocity, roof-mean-square deviation of the differential pressure.
ON FILTRATION SCHEMES OCCURRING IN THE PROBLEM OF FLOW OVER A ZHUKOVSKII SHEET PILE
É. N. Bereslavskii
Consideration is given to fi ltration under a Zhukovskii sheet pile through a ground layer underlain by a highly permeable head horizon the left semiinfi nite part of whose roof is modeled by an impermeable base. A study is made of the case of fl ow where the velocity at the end of the sheet pile is equal to infi nity and the fl ow rate takes on extremum values on both water-permeable portions of the boundary of the region of motion. Limiting cases of fl ow associated with the absence of upthrust and of an impermeable inclusion alike are noted, as is an adjacent scheme due to the absence of the two indicated extremum points. Solutions are given for two schemes of motion in a semiinverse formulation, with the classical Zhukovskii problem being the limiting case of one scheme. Distinctive
features of such models are noted. For investigation of these fl ows, use is made of a Polubarinova-Kochina method which allows exact analytical representations for motion elements. Results of numerical calculations and the analysis of the infl uence of all physical factors on fi ltration characteristics are given.
Keywords: filtration, groundwater, Zhukovskii sheet pile, infi ltration, upthrust, complex fl ow velocity, conformal mappings, Polubarinova-Kochina method.
DETERMINATION OF THE TIME OF ACCUMULATION OF A LIQUID IN PERIODIC GAS-LIFT WELLS
É. M. Abbasov
The time of accumulation of a liquid in a periodic gas-lift well, during which the discharge of the well reaches a maximum value, was determined on the basis of theoretical investigations. It is shown that, for a concrete well, this time is determined by the parameters of the pool–well system, the gas, and the liquid produced.
Keywords: periodic gas lift, accumulation of a liquid in a well, pool, discharge of the well, liquid produced.
COMBINED TIMBER DRYING METHOD
M. A. Goreshnev, A. N. Kazarin, V. V. Lopatin,
F. G. Sekisov, and O. V. Smerdov
This paper presents the results of investigations of the moisture and temperature distribution in drying by the
conduction method, by means of a radio-frequency electromagnetic fi eld, and by the combined method of heating at a low pressure. The rate of drying by the combined heating method is twice higher than in conduction heating and 1.5 times higher than in radio-frequency heating at the same energy input to the wood. The fi nite moisture content of the wood in drying by the combined method is much lower than in drying by the other methods, and the moisture gradient in the thickness of the specimen does not exceed 5%. On the basis of the results of investigations a pilotproduction
vacuum drier with a loading volume of 1 m3 has been created.
Keywords: timber drying, combined drying, drying by radio-frequency currents, moisture distribution.
PROBLEM OF ELECTROMAGNETIC DRYING OF A SPHERE
A.M. Afanas’ev and B. N. Siplivyi
We propose a time-asymptotic analytical solution of the initial boundary-value problem for temperature and moisturecontent fi elds in electromagnetic drying of a spherical specimen. The solution makes it possible to calculate in the fi rst approximation the main drying characteristics, classify its possible regimes, and optimize these regimes in terms
of the most important parameters.
Keywords: electromagnetic drying, A. V. Luikov equations, fi rst drying period, spherically symmetric solution of the initial boundary-value problem, asymptotic solution, drying quality.
BROWNIAN DIFFUSION INSIDE A MICRON-SIZED DROPLET AND THE MORPHOLOGY OF ENSEMBLES OF NANOPARTICLES
S. P. Fisenko and Yu. A. Khodyko
Three types of morphologies of ensembles of nanoparticles inside the evaporating micron-sized droplet of a solution at a low pressure have been described on the basis of experimental and theoretical results. It has been shown that the basic processes inside the droplet that infl uence the morphology are the coalescence of nanoparticles and their Brownian diffusion. Parametrically, all the processes are infl uenced by the rate of evaporation of the droplet. It has been found that a higher-than-average concentration of nanoparticles at the droplet’s edge, which gives rise to
"hollow"-type structures of agglomerated nanoparticles, develops in rapid evaporation. It has been shown that the fi nal morphology of nanoparticles can be infl uenced by changing the viscosity of the solution droplet or the total pressure in the reactor.
Keywords: evaporation rate, Brownian diffusion coeffi cient, coalescence, Galerkin method.
SEPARATION OF A GASEOUS MIXTURE IN NANOSIZE CHANNELS. THE ROLE OF SURFACE DIFFUSION
V. M. Zhdanov,a V. I. Roldugin,b and E. E. Sheryshevab
The separation coeffi cient has been calculated for membranes with nanometer-size pores. In the calculations, account was taken of surface diffusion and of the dependence of the surface-diffusion coeffi cient on the surface coverage which was determined within the framework of the Langmuir isotherm describing competing adsorption.
An analytical solution of the problem has been obtained for mixture fl ow in single-layer membranes. It has been shown that in the case of a mixture we have the mutual infl uence of the components on the transfer even in the absence of their formal interaction. In ultrathin channels, there can be a situation where the character of separation of the components is reversed compared to that predicted in the model of free-molecular mixture fl ow.
Keywords: membranes, nanosize pores, mixture fl ow, separation coeffi cient, adsorption, surface diffusion, mutual
infl uence of the components.
PHYSICOCHEMICAL PROPERTIES OF CARBON NANOTUBES OBTAINED FROM PEAT MOSS
D. V. Onishchenko and V. P. Reva
It has been established that mechanochemical treatment of amorphous carbon synthesized by pyrolysis from brown peat moss leads to the formation of carbon nanotubes. Complex studies of the sorptive properties of pyrolytic amorphous carbon and multiwalled nanotubes obtained from peat moss have been made. It has been shown that the ability of carbon nanotubes for acidic modifi cation depends on the technological parameters of their formation, and
the effi ciency of the sorptive capacity volume of such nanotubes depends on their storage time. The possibility of using carbon materials from peat moss as effective enterosorbents has been considered.
Keywords: brown peat moss, pyrolysis, mechanoactivation, nanofi brous carbon, multiwalled nanotubes, acidity of carbon nanotubes, sorptive capacity.
HYDROGASDYNAMICS IN TECHNOLOGICAL PROCESSES
BALANCE METHOD OF CALCULATING THE CHARACTERISTICS OF A REPEATED FLOODING OF NUCLEAR REACTORS
IN PROJECTED ACCIDENTS
S. S. Bazyuk,a N. Ya. Parshin,a E. B. Popov,a and Yu. A. Kuzma-Kichtab
A balance method is proposed for calculating the main characteristics of the cooling of the heat-releasing assemblies of light-water nuclear reactors in the case of repeated fl ooding of them at the bottom under the conditions of a maximum projected accident. The calculation data obtained by this method agree well with the corresponding results of experiments in the temperature range of up to 1200oC. The method proposed allows one not only to calculate the
parameters of the fl ooding of a heat-releasing assembly under the conditions of an accident, but also to estimate the fl ow rate of the water and the time, necessary for fl ooding of the fuel core of a power unit in the case of its damage that is not due to the breakage of a pipe-line.
Keywords: repeated fl ooding and cooling of a heat-releasing assembly, infl ation, depressuration and oxidation of the shells of fuel elements, fl ooding front.
AERODYNAMIC DRAG TO FLOWS ABOUT SINGLE DROP-LIKE TUBES
AND VISUALIZATON OF THESE FLOWS
M. Terekh,a A. I. Rudenko,b and Yu. V. Zhukovab
Results of experimental investigations of the aerodynamic drag to the cross fl ows about single tubes of drop-like shape in the range of change in the Reynolds number from 9000 to 45,000 are presented. The results obtained were compared with the corresponding experimental data obtained for single round tubes. A visualization of the fl ows over the surfaces of single drop-like and round tubes has been carried out.
Keywords: drop-like and round tubes, aerodynamic drag, visualization.
ELECTRIC ARC IN A GAS FLOW AS AN EXAMPLE OF A HEAT WAVE
G. V. Tkachenko and B. A. Uryukov
The conditions under which a sharp thermal layer boundary is formed around an electric arc burning in a cocurrent gas fl ow are considered. It is shown that this effect may be interpreted as a heat wave whose boundary represents a slight discontinuity across which there occurs a jump in the gradients of the thermodynamic properties of the medium, in particular, in the heat fl ux. In contrast to the heat wave investigated theoretically by Barenbladt and Zel’dovich, in the case at hand the gas stream entering into the thermal layer plays an important role. A self-similar solution of the problem is obtained on the assumption that electrical conductivity depends exponentially on the thermal potential.
Keywords: electric arc, heat wave, self-similar solution.
INFLUENCE OF A LIQUID-CRYSTAL ADDITIVE ON THE STRUCTURAL
CHARACTERISTICS OF THE ORIENTATIONALLY ORDERED NEAR-SURFACE LAYERS OF A PETROLEUM OIL
S. V. Kiriyan,a B. A. Altoiz,b and E. A. Shataginab
It has been established that a shear fl ow of a micron interlayer of a petrolatum oil doped with a nematic liquid crystal or a surface-active substance (oleic acid) is non-Newtonian in character. This was explained by the existence of orientationally ordered near-wall layers on the substrate confi ning the indicated interlayer. The parameters of the structure of such a near-wall layer were estimated within the framework of the rheological model of a heterophase stratifi ed interlayer. It is shown that the thickness and molecular ordering of an interlayer of a petrolatum oil with a liquid-crystal additive are larger than those of an interlayer of this oil doped with a surface-active substance.
Keywords: base model lubricant, additive, liquid crystal, surface-active substance, epiropic liquid crystal, structural
HYDRODYNAMIC ENTRANCE LENGTH FOR HIGH-VISCOSITY
NEWTONIAN FLUID FLOW IN AN ANNULAR CHANNEL
A. V. Ryazhskikh and S. V. Ryabov
An analytical solution has been obtained to the problem of identifi cation of the entrance length in a horizontal annular channel for the laminar head fl ow of a high-viscosity Newtonian fl uid.
Keywords: laminar fl ow, high-viscosity Newtonian fl uid, horizontal annular channel, hydrodynamic entrance length.
SOURCES OF VISCOUS LIQUID
S. K. Betyaev
The classifi cation of the sources of an incompressible liquid has been made and a theory of fl ows with vortex sources has been suggested. The solutions of the Navier−Stokes equations in the form of linear and point sources of liquid are considered. Spiral sources are investigated. The problem of cutting-off of a linear source has been posed and
Keywords: vortex, spiral, and point sources of liquid; source strength, Trefftz plane.
DISTRIBUTION OF VISCOUS LIQUID FLOW VELOCITY IN A PIPELINE
ON HYDRAULIC SHOCK
I.V. Kudinov, V. A. Kudinov, and A. V. Eremin
UDC 536.2 (075)
An exact analytical solution to the boundary-value problem of hydrodynamics has been obtained. It describes the velocity distribution along the pipeline length in time with reference to a real viscous incompressible liquid flow under hydraulic shock conditions.
Keywords: viscous incompressible liquid, hydraulic shock, velocity, pressure, hydraulic resistance, hyperbolic
equation, exact analytical solution, Fourier method, orthogonal methods.
COMPUTATIONAL MODELING OF THE HEAT EXCHANGE
BETWEEN THE HEAT-TRANSPORT MEDIUM AND THE AIR
IN A ROOM WITH FLOOR HEATING
B. I. Basok, A. N. Nedbailo, M. P. Novitskaya, M. V. Tkachenko, and S. M. Goncharuk
This paper presents the results of computational modeling of the heat exchange between the heat-transport medium and the air in a room with fl oor heating. The modeling results are comparable with experimental data. A good agreement between calculations and experiments is noted. Graphs of the fl oor heating loads for various pitches of pipe laying in the fl oor have been obtained by the method of computational modeling.
Keywords: floor heating, heat exchange in the room, computational modeling, experiment.
OPTIMIZATION OF THE FREE CONVECTION FROM A VERTICAL ARRAY
OF ISOTHERMAL HORIZONTAL ELLIPTIC CYLINDERS
VIA GENETIC ALGORITHM
T. Yousefi ,a A. Karami,b E. Rezaei,b and E. Ghanbaria
The present paper is devoted to the optimization of the cost function in free convective heat transfer from a vertical array of isothermal horizontal elliptic cylinders on the basis of the genetic algorithm (GA). The input parameters include the ratio of the cylinder spacing to the cylinder major axis varying from two to fi ve and the Rayleigh number ranging from 103 to 2.5·103. The regression equation for the average Nusselt number is based on experimental data obtained as a function of the parameters mentioned. The cost function is optimized using the GA. The results indicate that the proposed algorithm is effi cient enough to be used for optimizing the cost function.
Keywords: free convection, elliptic cylinder, v ertical array, optimization, g enetic algorithm (GA).
MASS TRANSFER EFFECTS ON THE UNSTEADY MHD RADIATIVE– CONVECTIVE
FLOW OF A MICROPOLAR FLUID PAST A VERTICAL POROUS PLATE
WITH VARIABLE HEAT AND MASS FLUXES
M. Gnaneswara Reddy
The problem of unsteady two-dimensional laminar fl ow of a viscous incompressible micropolar fl uid past a vertical porous plate in the presence of a transverse magnetic fi eld and thermal radiation with variable heat and mass fl uxes is considered. The free stream velocity is subjected to exponentially increasing or decreasing small perturbations.
A uniform magnetic fi eld acts perpendicularly to a porous surface where a micropolar fl uid is absorbed with a suction velocity varying with time. The Rosseland approximation is used to describe radiative heat transfer in the limit of optically thick fl uids. The effects of the fl ow parameters and thermophysical properties on the velocity and temperature fi elds across the boundary layer are investigated. The effects of various parameters on the velocity, microrotation velocity, temperature, and concentration profi les are given graphically, and the values of the skin friction and couple stress coeffi cients are presented.
Keywords: unsteady flow, micropolar fl uid, mixed convection, MHD, radiation, mass transfer.
ON THE MOTION OF A CYLINDRICAL CONTAINER IN A CIRCULAR PIPE
UNDER THE ACTION OF A LIQUID FLOW
V. A. Babkin
From the viewpoint of the anisotropic near-wall turbulence model an analytical solution of the problem of axially symmetric motion of a cylindrical container of neutral buoyancy caused by an incompressible turbulent fl ow in a straight circular pipe has been obtained. This analytical solution agrees with experiments. It establishes the relations between the mean velocity in the pipe and the container velocity and between the velocity gradient in the pipe and the velocity gradient in the gap between the pipe wall and the side wall of the container.
Keywords: enforced flow, near-wall turbulence, two-layer velocity profi le, relative velocity of the container.
HEAT CONDUCTION AND HEAT TRANSFER IN TECHNOLOGICAL PROCESSES
ANALYTICAL SOLUTION OF NONSTATIONARY HEAT CONDUCTION PROBLEM
FOR A HALF-SPACE WITH A MULTILAYER COATING
V. A. Shevchuk
Based on the use of generalized boundary conditions, an analytical solution of the one-dimensional nonstationary heat conduction problem has been obtained by the method of integral Laplace transform for a half-space with a multilayer coating. Investigation was carried out and the laws governing the progress of the thermal process in the solid body and coating heated convectively by the external medium have been derived.
Keywords: heat conduction, half-space, multilayer coating, generalized boundary conditions.
ANALYTICAL EQUATION FOR CALCULATING THE ADIABATIC TEMPERATURE
OF THE WET-BULB THERMOMETER
A. P. Baskakov and O. A. Rakov
A formula for calculating the adiabatic temperature of the wet-bulb thermometer has been obtained analytically without using the analogy between the heat and mass transfer processes. A comparison of the results of calculations with the use of this formula and formulas of other authors used in the technical literature has been made.
Keywords: adiabatic temperature, wet-bulb thermometer.
DETERMINATION OF THERMAL DIFFUSIVITY AND NONLOCALIZATION PARAMETERS FROM EXPERIMENTAL DATA
M. R. Shabanova
Based on the solution of the nonlocal heat conduction equation in fractional calculus and on experimental data for nonstationary methods of determining temperature distribution, a method of determining the thermal diffusivity and parameters of nonlocalization in time and space has been developed.
Keywords: thermal diffusivity, parameters of nonlocalization in time and space, nonstationary method of determining
MISCELLANEA GEOMETRICALLY NONLINEAR PARAMETRIC VIBRATIONS OF A TRANSVERSELY STRAIGHTENED CYLINDRICAL SHELL IN THE PROCESS OF ITS DYNAMIC INTERACTION WITH A MEDIUM
F. S. Latifov, F. A. Seifullaev, and A. O. Yuzbashieva
The problem on the parametric vibrations of a transversely straightened cylindrical shell contacting with a viscoelastic medium under the action of the internal pressure was solved on the basis of the variation principle in the geometrical nonlinear formulation. The infl uence of the environment on the indicated vibrations was estimated with the use of the Pasternak dynamic model.
Keywords: vibrations, cylindrical shell, Pasternak model, transversal rod; critical force.
SWITCHING AND VALVE-LIKE PROPERTIES
OF AN AL−AL2O3−AG2SE−AG MOS STRUCTURE
G. S. Gadzhieva, I. A. Akhmedov, and N. N. Abdul-zade
In investigating the volt-ampere characteristic of an Al−Al2O3−Ag2Se−Ag (metal−oxide−semiconductor) structure, it has been found that polarity-dependent effects of switchover and memory are stably observed in it in a wide temperature range (77−400 K). In the region of phase transition of argentum selenide (400−406 K), there are manifested valve-like properties, with the result that electrical conductivity decreases by three to four orders of magnitude.
Keywords: switching element, valve-like element, thermal relay, multifunctional commutator.