Volume 91, №1
THE THEORY OF THERMODYNAMIC SYSTEMS WITH INTERNAL VARIABLES OF STATE: NECESSARY AND SUFFICIENT CONDITIONS FOR COMPLIANCE WITH THE SECOND LAW OF THERMODYNAMICS
Based on the entropy-free thermodynamic approach, a generalized theory of thermodynamic systems with internal variables of state is being developed. For the case of nonlinear thermodynamic systems with internal variables of state and linear relaxation, the necessary and suffi cient conditions have been proved for fulfi llment of the second law of thermodynamics in entropy-free formulation which, according to the basic theorem of the theory, are also necessary and suffi cient for the existence of a thermodynamic potential. Moreover, relations of correspondence between thermodynamic systems with memory and systems with internal variables of state have been established, as well as some useful relations in the spaces of states of both types of systems
Author: A. I. Shnip
Keywords: thermodynamics, systems with internal variables, systems with memory, second law of thermodynamics, thermodynamic potential
BOUNDARIES OF THE REALIZABILITY REGION OF MEMBRANE SEPARATION PROCESSES
The region of realizability of membrane separation systems having a constant total membrane area has been determined for a defi nite output of a fi nal product at a defi nite composition of a mixture flow. The law of change in the pressure in the mixture, corresponding to the minimum energy required for its separation, was concretized for media close in properties to ideal gases and solutions.
Author: A. M. Tsirlin and A. A. Akhrenemkov
Keywords: realizability region, membrane separation, mixture
HEAT-FLUX SENSORS INTEGRATED INTO THE STRUCTURE OF THERMAL PROTECTION COATINGS
In designing heat-loaded structural elements of descent modules, information on heat loads (heat fl uxes and surface temperatures) throughout the active stage of fl ight in the atmosphere is primary. When a spacecraft moves with hypersonic velocities, the level of temperature and processes occurring on the thermal-protection surface does not necessarily make it possible to use traditional tools to measure heat loads. In this case an alternative to direct measurements is provided by determining heat loads from the data of temperature measurements at several internal points of the structural elements of the thermal protection. The objective of the present work is to develop and evaluate sensors for measurement of the heat loading of thermal protection coatings of today′s descent modules. In the paper, consideration is given to heat-fl ux sensors for two classes of thermal protection materials: nondestructible fi brous materials and thermally destructible polymers.
Author: O. M. Alifanov, S. A. Budnik, A. V. Morzhukhina, A. V. Nenarokomov, A. V. Netelev, and D. M. Titov
Keywords: heat-fl ux sensors, thermal protection, inverse problems, iterative regularization, heat-insulating materials, decomposable polymer materials
MATHEMATICAL MODEL OF HEAT TRANSFER IN THE CATALYST GRANULE WITH POINT REACTION CENTERS
This paper considers a catalyst granule with a porous ceramic chemically inert base and active point centers, at which an exothermic reaction of synthesis takes place. The rate of a chemical reaction depends on temperature by the Arrhenius law. The heat is removed from the catalyst granule surface to the synthesis products by heat transfer. Based on the idea of self-consistent fi eld, a closed system of equations is constructed for calculating the temperatures of the active centers. As an example, a catalyst granule of the Fischer–Tropsch synthesis with active metallic cobalt particles is considered. The stationary temperatures of the active centers are calculated by the timedependent technique by solving a system of ordinary differential equations. The temperature distribution inside the granule has been found for the local centers located on one diameter of the granule and distributed randomly in the granule′s volume. The existence of the critical temperature inside the reactor has been established, the excess of which leads to substantial superheating of local centers. The temperature distribution with local reaction centers differs qualitatively from the granule temperature calculated in the homogeneous approximation. The results of calculations are given.
Author: I. V. Derevich and A. Yu. Fokina
Keywords: Fischer–Tropsch synthesis, catalytic reactions, metallic cobalt, Legendre polynomials, thermal effect of synthesis reaction, synthesis gas, porous granule of a catalyst, thermal explosion
THERMOHYDRAULIC EFFICIENCY OF TUBES WITH INTERNAL SPIRAL FINNING
The authors have presented results of experimental investigation into the hydrodynamics and heat transfer during the water flow in a tube with internal spiral finning at angles of twist from 14 to 87o , and also of visualization of the flow structure from numerical-simulation results
Author: A. N. Skrypnik, A. V. Shchelchkov, I. A. Popov, D. V. Ryzhkov, S. A. Sverchkov, Yu. V. Zhukova, A. D. Chornyi, and N. N. Zubkov
Keywords: enhancement of heat transfer, hydraulic loss, tube with internal spiral finning
HEAT TRANSFER IN AIR FLOW ACROSS A SINGLE-ROW BUNDLE OF TUBES WITH SPIRAL GROOVES
An experimental study has been made of the heat transfer and hydraulic resistance in air flow across a single-row bundle of tubes with spiral grooves on the exterior surface and of a bundle of smooth tubes of the same diameter. Cutting a spiral groove of width 3 mm and depth 2 mm with a pitch of 20 mm on a tube with an outside diameter of 22 mm increased the heat-transfer coefficient in the range of Reynolds numbers 6200–16,000 by 40–53% compared to the smooth-tube bundle. The hydraulic resistance of the tube bundle decreased by 22%. The Reynolds analogy factor increased, on the average, by 41%. Tubes with spiral grooves, in the investigated range of the velocities of flow, have shown a certain increase in the Strouhal number to values of 0.24–0.36. Computer simulation has been carried out of the hydrodynamics of the single-row bundle of smooth-wall tubes and the tubes with spiral grooves. It has been shown that the enhancement of heat transfer and the decrease in the hydraulic resistance alike are attributable to the appearance of nonsymmetric vortex structures induced by the fl ow across the spiral grooves.
Author: A. A. Khalatov, G. V. Kovalenko, and A. Zh. Meiris
Keywords: enhancement of heat transfer, heat transfer, hydraulic resistance, flow across tubes, spiral grooves
CONTROLLING THE INTERNAL HEAT TRANSFER COEFFICIENT BY THE CHARACTERISTICS OF EXTERNAL FLOWS
The engineering-physical fundamentals of substance synthesis in a boiling apparatus are presented. We have modeled a system of automatic stabilization of the maximum internal heat transfer coeffi cient in such an apparatus by the characteristics of external fl ows on the basis of adaptive seeking algorithms. The results of operation of the system in the shop are presented.
Author: V. M. Zhuromskii
Keywords: boiling apparatus, heat transfer coeffi cient, automatic extremum seeking algorithm
ASSESSMENT OF THERMAL PERFORMANCE OF FUNCTIONALLY GRADED MATERIALS IN LONGITUDINAL FINS
Assessment of the thermal characteristics of materials in heat exchangers with longitudinal fi ns is performed in the case where a conventional homogeneous material of a longitudinal fi n is replaced by a functionally graded one, in which the fin material properties, such as the conductivity, are assumed to be graded as linear and power-law functions along the normal axis from the fi n base to the fi n tip. The resulting equations are calculated under two (Dirichlet and Neumann) boundary conditions. The equations are solved by an approximate analytical method with the use of the mean value theorem. The results show that the inhomogeneity index of a functionally graded material plays an important role for the thermal energy characteristics in such heat exchangers. In addition, it is observed that the use of such a material in longitudinal fi ns enhances the rate of heat transfer between the fi n surface and surrounding fl uid. Hopefully, the results obtained in the study will arouse interest of designers in heat exchange industry.
Author: R. Hassanzadeh and M. Bilgili
Keywords: functionally graded material, heat transfer rate enhancement, inhomogeneity index, mean value theorem
NUMERICAL INVESTIGATION OF THE LOW-PRESSURE EVAPORATIVE COOLING OF A SUBSTRATE
A mathematical model for determining the interrelationship between the velocity of motion of the evaporation front and the thermal processes in the substrate has been developed. We have calculated the values of heat fl uxes from the substrate in the process of evaporation of a fi lm of thickness several microns and femtoliter water droplets. It has been shown that the heat fl uxes in the evaporation time are of the order of 1 MW/m2 . The evaporation time does not exceed 10–2 s. Approximated formulas have been obtained for estimating the values of heat fl uxes. It has been established that a decrease in pressure increases the value of the measured heat fl ux due to the decrease in the limiting temperature of the evaporation front.
Author: S. P. Fisenko and Yu. A. Khodyko
Keywords: evaporation front, free-molecular regime, film, pinning-effect, heat flux
EVAPORATION OF WATER DROPLETS MOVING THROUGH HIGH-TEMPERATURE GASES
With the use of high-speed recording and diagnostic facilities, an experimental study has been made of the evaporation of droplets (of characteristic size Rm ≈ 0.05–0.035 mm) of atomized fl ow of water-based suspensions with typical soil impurities (silt and clay) moving in a high-temperature (about 1100 K) gaseous medium (with the example of acetone combustion products). The relative mass concentration of soil components in the suspension was varied over the range of γ = 0–1%. A strong infl uence of the above impurities on the main characteristic of evaporation — the relative change in the droplet radius ΔR — has been established. The infl uence of the initial temperature (varied over the range of Tw = 278–320 K) of the atomized suspension on the evaporation rate of the latter has been determined. It has been shown that the values of integral characteristics of the process of evaporation of suspensions with soil impurities can be much (2–3 times) higher than for water without these components.
Author: G. V. Kuznetsov and P. A. Strizhak
Keywords: droplet, suspension, soil impurities, high-temperature gases, heat transfer, evaporation, high-speed video recording
NUMERICAL STUDY OF MIXING THERMAL CONDUCTIVITY MODELS FOR NANOFLUID HEAT TRANSFER ENHANCEMENT
Researchers have paid attention to nanofl uid applications, since nanofl uids have revealed their potentials as working fl uids in many thermal systems. Numerical studies of convective heat transfer in nanofl uids can be based on considering them as single- and two-phase fl uids. This work is focused on improving the single-phase nanofl uid model performance, since the employment of this model requires less calculation time and it is less complicated due to utilizing the mixing thermal conductivity model, which combines static and dynamic parts used in the simulation domain alternately. The in-house numerical program has been developed to analyze the effects of the grid nodes, effective viscosity model, boundary-layer thickness, and of the mixing thermal conductivity model on the nanofl uid heat transfer enhancement. CuO–water, Al2O3–water, and Cu–water nanofl uids are chosen, and their laminar fully developed fl ows through a rectangular channel are considered. The infl uence of the effective viscosity model on the nanofl uid heat transfer enhancement is estimated through the average differences between the numerical and experimental results for the nanofl uids mentioned. The nanofl uid heat transfer enhancement results show that the mixing thermal conductivity model consisting of the Maxwell model as the static part and the Yu and Choi model as the dynamic part, being applied to all three nanofl uids, brings the numerical results closer to the experimental ones. The average differences between those results for CuO–water, Al2O3–water, and CuO–water nanofl uid fl ows are 3.25, 2.74, and 3.02%, respectively. The mixing thermal conductivity model has been proved to increase the accuracy of the single-phase nanofl uid simulation and to reveal its potentials in the single-phase nanofl uid numerical studies
Author: A. Pramuanjaroenkij, A. Tongkratoke, and S. Kakaç
Keywords: nanofl uid, mixing thermal conductivity model, single phase, boundary layer
INFLUENCE OF AGGLOMERATION ON THE VISCOSITY OF NANOFLUIDS
A model of the associated layer on the surface of nanoparticles in a fl uid, which makes up mechanically integrated inclusions with them, has been proposed. Such inclusions can primarily be considered as solid particles with a diameter larger than their nucleus. This can be interpreted as the effective increase in the volume concentration of primary particles, which makes it possible to adapt the existing Batchelor formula to describe the results of measurements of the nanofl uid viscosity. The inevitability of the agglomeration of nanoparticles in view of the associated fl uid layer being present on their surface has also been demonstrated. It has been shown that the effective volume concentration depends on the size of primary nanoparticles and the degree of their agglomeration. Furthermore, data have been presented according to which the associated-layer thickness for particles with a diameter under 20 mm becomes dependent on the nanoparticle size.
Author: A. P. Zav′yalov, V. V. Syzrantsev, K. V. Zobov, and S. P. Bardakhanov
Keywords: nanofl uid, viscosity, agglomeration, porosity
STUDY OF THE MIXING REGIMES OF A FLUID AND A NANOFLUID IN A T-SHAPED MICROMIXER
In the present paper, the regimes of fl ow and mixing of water and a nanofl uid with aluminum oxide nanoparticles in a T-shaped microchannel have been studied numerically. The Reynolds number was varied from 10 to 400, and the volume concentration of nanoparticles was varied from 0 to 10%. Nanofl uids with mean sizes of particles from 50 to 150 nm were considered. The viscosity coeffi cient of the nanofl uid was taken from experimental data. In all cases, it exceeded the viscosity coeffi cient of water and depended on not only the concentration of nanoparticles, but also on their sizes, and the viscosity of the nanofl uid with smaller particles was higher than the viscosity of the nanofl uid with large particles. It has been established that there exist regimes of steady irrotational fl ow, steady vortex fl ow with two horseshoe vortices, and steady fl ow with two vortices in the mixing channel. It has been shown that when the fl ow goes from the regime with horseshoe vortices to the fl ow conditions with two single vortices, the mixing effi ciency increases several times. It has been established that the fl ow conditions and the mixing effi ciency largely depend on the volume concentration of particles and their sizes.
Author: A. S. Lobasov, A. V. Minakov, and V. Ya. Rudyak
Keywords: hydrodynamics, numerical simulation, T-shaped micromixer, micromixer, mixing, viscosity, nanofl uid, nanoparticles, pressure drop
SIMULATION OF THE DYNAMICS OF ISOTHERMAL GROWTH OF SINGLE-LAYER GRAPHENE ON A COPPER CATALYST IN THE PROCESS OF CHEMICAL VAPOR DEPOSITION OF HYDROCARBONS
A new kinetic model of isothermal growth of single-layer graphene on a copper catalyst as a result of the chemical vapor deposition of hydrocarbons on it at a low pressure has been developed on the basis of in situ measurements of the growth of graphene in the process of its synthesis. This model defi nes the synthesis of graphene with regard for the chemisorption and catalytic decomposition of ethylene on the surface of a copper catalyst, the diffusion of carbon atoms in the radial direction to the nucleation centers within the thin melted near-surface copper layer, and the nucleation and autocatalytic growth of graphene domains. It is shown that the time dependence of the rate of growth of a graphene domain has a characteristic asymmetrical bell-like shape. The dependences of the surface area and size of a graphene domain and the rate of its growth on the time at different synthesis temperatures and ethylene concentrations have been obtained. Time characteristics of the growth of graphene domains depending on the parameters of their synthesis were calculated. The results obtained can be used for determining optimum regimes of synthesis of graphene in the process of chemical vapor deposition of hydrocarbons on different catalysts with a low solubility of carbon.
Author: S. I. Futko, B. G. Shulitskii, V. A. Labunov, and E. M. Ermolaeva
Keywords: graphene, carbon allotropes, in situ graphene growth dynamics, chemical vapor deposition, copper catalyst, heterogeneous catalyst, transition metals, hydrocarbons
RHEOLOGICAL PROPERTIES OF RUBBER COMPOUNDS WITH FINELY DIVIDED CARBON ADDITIVES
A study has been made of the infl uence of three different nanomaterials: of the starting material, and also of those functionalized by amine and oxygen-containing groups, on the properties of elastomer compositions based on rubbers for special purposes. As the elastomer matrix, use was made in one case of a rubber compound based on BNKS-18 butadiene-nitrile rubber and in the other, of a combination of two grades of butadiene-nitrile rubber (BNKS-18 + BNKS-28 in a 50:50 ratio), which differed by the amount of the bound nitrile of acrylic acid. To determine the degree of interaction between the additives and the elastomer matrix, the authors carried out multiple tests of the rubber compounds. The indices of plastoelastic properties of the rubber compounds and the qualitative characteristics of distribution of the fi ller (elastic modulus at small deformation amplitudes and the shear modulus under large deformation) and the difference in these indices (complex dynamic modulus) alike have been determined.
Author: Zh. S. Shashok, N. R. Prokopchuk, K. V. Vishnevskii, A. V. Krauklis,b K. O. Borisevich, and I. O. Borisevich
Keywords: butadiene-nitrile rubber, elastic modulus, shear modulus, complex dynamic modulus, Mooney viscosity, carbon nanomaterials, nanotubes, nanofi bers, functionalization
EXCITATION OF SHOCK WAVES IN THE PASSAGE OF DETONATION THROUGH THE REGION OF MIXING OF REACTING AND INERT GASES
A nonstationary problem on the excitation of a plane shock wave as a result of the passage of detonation through the region of mixing of a reacting and an inert gases has been formulated and solved numerically. The formulation of this problem is based on the approximate model defi ning, with a high accuracy, the change in the molar mass and specifi c internal energy of the combustion products of hydrocarbons caused by a shift of them from their chemicalequilibrium position. A situation in which, in the region of mixing of the reacting and inert gases, their concentrations change linearly was considered. The infl uence of the width of the mixing region on the intensity of the excited shock waves and the law of their attenuation was investigated.
Author: E. S. Prokhorov
Keywords: gas detonation, reacting and inert gases, detonation products, chemical equilibrium, shock wave
NUMERICAL INVESTIGATION OF THE INFLUENCE OF THE CONFIGURATION PARAMETERS OF A SUPERSONIC PASSENGER AIRCRAFT ON THE INTENSITY OF SONIC BOOM
Results of calculations of the sonic boom produced by a supersonic passenger aircraft in a cruising regime of fl ight at the Mach number M = 2.03 are presented. Consideration is given to the infl uence of the lateral dihedral of the wings and the angle of their setting, and also of different locations of the aircraft engine nacelles on the wing. An analysis of parametric calculations has shown that the intensities of sonic boom generated by a confi guration with a dihedral rear wing and by a confi guration with set wings remain constant, in practice, and correspond to the intensity level created by the optimum confi guration. Comparative assessments of sonic boom for tandem confi gurations with different locations of the engine nacelles on the wing surface have shown that the intensity of sonic boom generated by the confi guration with an engine nacelle on the windward side can be reduced by ~14% compared to the confi guration without engine nacelles. In the case of the confi guration with engine nacelles on the leeward size of the wing, the profi le of the sonic-boom wave degenerates into an N-wave, in which the intensity of the bow shock is signifi cantly reduced.
Author: V. F. Volkov and I. I. Mazhul′
Keywords: supersonic fl ow, sonic boom, monoplane, tandem confi guration, dihedral of the wing, engine nacelles
AN EXPERIMENTAL MODEL FOR INVESTIGATING THE DYNAMICS OF MAGNETIC DISPERSIONS IN A GRADIENT MAGNETIC FIELD
An experimental model is suggested for investigating the motion of magnetic dispersions under the action of mechanical and volumetric magnetic surface forces created respectively by a rotating cylinder and by the inhomogeneous fi eld of a transversely polarized cylindrical magnet. Using as an example a single magnetic ball, the characteristic features of motion attributable to the competition among the surface, magnetic, and inertial forces in the ″cylindrical magnet–rotating cylinder–quiescent cylinder″ system have been studied, including the critical frequency of the inertial slipping of dispersion from the rotating surface and the dynamic equilibrium of dispersion under the conditions of competition between the centrifugal slipping and magnetic capture.
Author: S. B. Kashevskii, B. É. Kashevskii,* and A. L. Khudolei
Keywords: magnetic disperse systems, motion in an inhomogeneous magnetic fi eld, experimental model, dynamics of a magnetic ball
ON CALCULATION OF INTENSE DESCENDING CONVECTION ABOVE A "COLD SPOT" ON A HORIZONTAL SURFACE
The author presents results of theoretical assessments referring to the convection that appears above a "cold spot" on a horizontal surface. Consideration is given to the case of thermal inhomogeneities with a fairly large amplitude where one cannot restrict oneself to a linear approximation. An analog of the Rayleigh number proportional to the amplitude of the temperature deviation and to the cube of the horizontal scale of the thermal inhomogeneity is a dimensionless criterion. From simple physical considerations and the scaling analysis, the author has obtained explicit analytical expressions for the depth (height) of penetration of thermal perturbations into a medium and for the amplitudes of convection-velocity components. These results are in good agreement with the experimental data available in the literature. The Nusselt number is proportional to the analog of the Rayleigh number to power 1/5; here, from a comparison with the experimental results, it follows that the proportionality factor is of the order of unity. The infl uence of the convection in question on the transfer of a passive impurity has been determined.
Author: L. Kh. Ingel′
Keywords: convection, nonuniform cooling from below, nonlinear model, scaling analysis, Nusselt number, transfer of an impurity
CONCENTRATION DISTRIBUTION OF SOLID PARTICLES IN THE COMPLETELY DEVELOPED TURBULENT FLOW IN A CHANNEL
The formation of regions with a higher concentration of solid particles in the completely developed turbulent flow in a channel with impermeable walls was investigated. A gas fl ow was simulated on the basis of nonstationary three-dimensional Navier–Stokes equations. The discrete-trajectory approach was used for simulation of the movement of particles. On the basis of the data of a direct numerical simulation, the distributions of the average and pulsating characteristics of the flow in the channel and the concentration distribution of the dispersed phase in it were determined. It was established that the formation of regions with a higher concentration of solid particles in the channel is due to the instantaneous redistribution of vorticity near its walls. The numerical-simulation data obtained are in qualitative and quantitative agreement with the corresponding results of physical and computational experiments.
Author: K. N. Volkov and V. N. Emel′yanov
Keywords: completely developed turbulent fl ow, solid particles, channel with impermeable walls, direct numerical simulation
VAPOR BUBBLE DYNAMICS IN DEUTERATED ACETONE
The results of numerical calculations of the vapor bubble dynamics in deuterated acetone are given.
Author: R. N. Khabeev and N. S. Khabeev
Keywords: small vapor bubble, deuterated acetone, radial vibrations, collapse
ATTENUATION OF THE ACOUSTIC SIGNAL PROPAGATING THROUGH A BUBBLY LIQUID LAYER
The acoustic signal dynamics in a fi ve-layer medium containing two liquid layers with polydisperse gas bubbles has been investigated. Calculations have been made for the interaction between the pulse perturbation of smallamplitude pressure and a multilayer sample containing two layers of industrial gel with polydisperse air bubbles. It has been shown that a small content of bubbles (about 0.1 vol. %) in a thin gel layer decreases tenfold or more the amplitude of acoustic waves with frequencies close to the resonance frequency of natural oscillations of bubbles. There are frequency ranges thereby where the infl uence of the bubbly layer is insignifi cant.
Author: D. A. Gubaidullin and A. A. Nikiforov
Keywords: bubbly liquid, acoustic waves, interphase heat and mass transfer, dispersion relation, polydispersity
EFFECT OF DISPERSED PHASE DISTRIBUTION ON THE SHOCK WAVE PARAMETERS IN A GAS SUSPENSION
The process of shock wave motion in an inhomogeneous medium is being studied numerically depending on the spatial distribution of the mean density of dispersed phase, that is, during the propagation of a shock wave from a pure gas into a gas suspension and from a gas suspension into a pure gas. The regularities have been revealed that affect the velocity and profi le of the shock wave moving in an inhomogeneous medium.
Author: D. A. Tukmakova, and N. A. Tukmakova
Keywords: gas suspension, shock wave, numerical simulation, interphase interaction
MATHEMATICAL MODELING OF MULTIPHASE FILTRATION IN POROUS MEDIA WITH A CHEMICALLY ACTIVE SKELETON
The authors propose a mathematical model of two-phase fi ltration that occurs under the conditions of dissolution of a porous medium. The model can be used for joint description of complex chemical-hydrogeomechanical processes that are of frequent occurrence in the oil-and-gas producing and nature conservation practice. As an example, consideration is given to the acidizing of the bottom zone of the injection well of an oil reservoir. Enclosing rocks are represented by carbonates. The phases of the process are an aqueous solution of hydrochloric acid and oil. A software product for computational experiments is developed. For the numerical experiments, use is made of the data on the wells of an actual oil fi eld. Good agreement is obtained between the fi eld data and the calculated data. Numerical experiments with different confi gurations of the permeability of an oil stratum are conducted.
Author: M. G. Khramchenkov and É. M. Khramchenkov
Keywords: mathematical model, two-phase fi ltration, deformable porous medium, chemically active fl uid, skin factor
ON THE PROBLEM OF FILTRATION TO AN IMPERFECT GALLERY IN A PRESSURELESS BED
The problem of plane steady-state fi ltration in a pressureless bed to an imperfect gallery in the presence of evaporation from the fl ow free surface is considered. To study such type of fl ow, a mixed boundary-value problem of the theory of analytical functions is formulated and solved with application of the Polubarinova-Kochina method. Based on the model suggested, an algorithm for computing the discharge of the gallery and the ordinate of free surface emergence to the impermeable screen is developed. A detailed hydrodynamic analysis of the infl uence of all physical parameters of the model on the desired fi ltration characteristics is given.
Author: É. N. Bereslavskii and L. M. Dudina
Keywords: fi ltration, pressureless bed, imperfect gallery, groundwater, free surface, evaporation, complex velocity, conformal mappings, Polubarinova-Kochina method
HEAT AND MASS TRANSFER IN THE DRYING OF A CYLINDRICAL BODY IN AN OSCILLATING MAGNETIC FIELD
A problem on the heating of a cylindrical body of infi nite length in an oscillating electromagnetic fi eld in the process of its drying has been formulated and solved analytically with account of the intermittence of irradiation of the body defi ned by the Heaviside unit function, the exponential-law absorption of electromagnetic energy by it, and the convective heat and mass exchange between the surface of the body and the environment having constant parameters. The intensity of evaporation of moisture from the surface of the body was determined on the basis of analytical solution of the problem on the mass transfer (moisture diffusion) in it on the assumption that the phase transformations of the body proceed near its surface. Solutions of the problem on the heating of the cylindrical body have been obtained for the cases of nonuniform and uniform distributions of its local temperature, the temperature of the body averaged over its volume, and the temperature gradient near the surface of the body. The "serviceability" of these solutions was verifi ed on the basis of numerical simulation, with them, of the drying of a seed shaped as a cylinder under the action of an oscillating infrared radiation. As a result of the numerical simulation performed, a technological regime of drying of seeds at minimum and maximum temperatures of their heating by on oscillating infrared radiation for a defi nite period of time in a cycle, providing not only the drying of the seeds but also substantial improvement of their sowing properties (the sprouting energy and the germination power), has been found. It is shown that the oscillating infrared heating of seeds can be used for their drying in pseudofl uidized and vibrofl uidized beds.
Author: S. P. Rudobashta, G. A. Zueva, and É. M. Kartashov
Keywords: electromagnetic heating, drying, convective heat and mass transfer, intermittent irradiation, thermolabile materials
INVESTIGATION OF REGULARITIES IN THE ENTRAINMENT OF PARTICLES FROM A CYCLONE-BED CHAMBER
Experimental investigation of the entrainment of quartz and olivine sand particles from a cyclone-bed chamber has been carried out. A generalized characteristic of the chamber is introduced that allows one to identify three different mechanisms of the entrainment.
Author: E. A. Pitsukha, Yu. S. Teplitskii, and É. K. Buchilko
Keywords: fl uidized bed, cyclone-bed chamber, entrainment of particles, Stokes number
QUASI-CAPILLARY EFFECT IN A FIXED AERATED GRANULAR BED
The phenomenon of spontaneous rise of solid particles in a narrow tube immersed in a fi xed aerated granular bed has been investigated experimentally. This phenomenon was called by us the quasi-capillary effect. It has been established that if a tube is immersed in a fi xed aerated granular bed, conditions are created inside the tube for intense motion of the solid phase, as a result of which the height to which the disperse medium rises inside the tube exceeds the height of the bulk granular bed. It is shown that the height of the solid phase rise and the character of the particle motion depend directly on the ratio of the inner tube diameter to the size of particles, as well as on the depth of tube immersion in the granular bed. The physical interpretation of this effect is given.
Author: V. N. Korolev, V. A. Markov, S. A. Nagornov, and I. S. Paryshev
Keywords: narrow tube, particle size, fi xed granular bed, solid particles, disperse medium
ON THE THEORY OF ACCUMULATION OF HYDROCARBONS IN A DOME USED TO ELIMINATE A TECHNOGENIC SPILL AT THE BOTTOM OF THE OCEAN
Consideration is given to the operation of a dome separator installed at the bottom of the World Ocean and intended to eliminate the effects of technogenic spill of hydrocarbons. It is assumed that oil and gas (methane) escape from the damaged well on the ocean fl oor. Under the conditions of stable existence of a hydrate, a hydration sheath is formed on the surface of methane bubbles. To collect the entering hydrocarbons, a dome from a soft polyurethane shell is installed above the spill site, inside which the hydrocarbons are accumulated. In the regime of steady-state operation of the dome, provision is made for pumping out of hydrocarbons for transportation and further utilization. In the work, temperature fi elds of the hydrocarbon layers accumulated in the dome are investigated.
Author: I. K. Gimaltdinov and S. R. Kil′dibaeva
Keywords: dome, hydrocarbon spill, shelf, oil, gas hydrates
SIMULATION OF THE PROCESSES OF FORMATION OF A DUST CLOUD IN A VACUUM AND IN THE ABSENCE OF GRAVITATION
This article is devoted to the simulation of the processes of formation of dust clouds in the absence of gravitation, which is necessary for understanding the processes proceeding in dust clusters in outer space, upper planetary atmosphere, and on the surface of space objects, as well as for evaluating the possibilities of creating disperse structures with given properties. The chief aim of the simulation is to determine the general laws of the dynamics of the dust cloud at the initial stage of its formation. With the use of the original approach based on the particle-in-cell method that permits investigating the mechanics of large ensembles of particles on contemporary computational platforms, we consider the mechanics of a dusty medium in the process of its excitation in a closed container due to the vibration of the walls, and then in the process of particle scattering when the container opens in outer space. The main formation mechanisms of a dust formation have been elucidated, and the possibilities of mathematical simulation for predicting spatial and time characteristics of disperse structures have been shown.
Author: A. V. Avdeev, A. S. Boreisho, S. V. Ivakin,c A. A. Moiseev,d A. V. Savin, E. I. Sokolov, and P. G. Smirnov
Keywords: dust cloud, particle-in-cell method, disperse structures, mathematical simulation, parallel calculations, Maxwell distribution
FLUCTUATION–DISSIPATION MODEL OF THE OPTICAL INFORMATION TRANSMISSION SYSTEM
The basic mechanisms underlying the fundamental fl uctuation losses in optical information-transmission systems have been studied. Account for these losses is of basic importance in analyzing light propagation to large distances.
Author: V. L. Kolpashchikov
Keywords: fl uctuation–dissipation model, optical information–transmission system, stochastic equations, temperature fl uctuations, fl uctuation losses