Volume 92, №5
NONSTATIONARY CONJUGATE PROBLEM OF HEAT TRANSFER IN SUPERSONIC FLOW PAST BODIES IN A WIDE RANGE OF REYNOLDS NUMBERS
In one of our earlier papers, we considered supersonic, laminar boundary-layer fl ows past bodies made of different materials and examined the possibility of controlling the temperature regime of a body immersed in fl ow. In the present work, for the conditions corresponding to aerodynamic experiments and to long fl ight times, we analyzed such values of deceleration parameters when regions of laminar, transitional, and turbulent regimes of fl ow are realized simultaneously in a boundary layer. The possibility of decreasing the level of maximal temperatures depending on the determining criteria of the problem has been evaluated for bodies made of different materials. The expediency of using simplifi ed approaches is shown, including those for nonstationary conditions based on stationary solutions and on well-studied limiting cases of isothermal and adiabatic surface temperatures and allowing the determination of the temperature regimes in the entire range of thermophysical characteristics In one of our earlier papers, we considered supersonic, laminar boundary-layer fl ows past bodies made of different materials and examined the possibility of controlling the temperature regime of a body immersed in fl ow. In the present work, for the conditions corresponding to aerodynamic experiments and to long fl ight times, we analyzed such values of deceleration parameters when regions of laminar, transitional, and turbulent regimes of fl ow are realized simultaneously in a boundary layer. The possibility of decreasing the level of maximal temperatures depending on the determining criteria of the problem has been evaluated for bodies made of different materials. The expediency of using simplifi ed approaches is shown, including those for nonstationary conditions based on stationary solutions and on well-studied limiting cases of isothermal and adiabatic surface temperatures and allowing the determination of the temperature regimes in the entire range of thermophysical characteristics
Author: V. I. Zinchenko and V. D. Gol′din
Keywords: aerodynamic heating, conjugate heat transfer, thermal-protective materials, turbulent boundary layer, heat fl ow along the surface, thermophysical characteristics of materials
INVERSE TRANSFORMS OF OPERATIONAL IMAGES IN MATHEMATICAL MODELS OF GENERALIZED PROBLEMS FOR HYPERBOLIC-TYPE EQUATIONS
Consideration has been given to a series of operational (after Laplace) nonstandard images whose inverse transforms are absent from the existing operational-calculus handbooks. The indicated images are involved in operational solutions to a wide class of generalized boundary-value problems based on hyperbolic-type equations that take account of the fi nite velocity of propagation of physical-fi eld potentials, and also in solutions to the problems of hydrodynamics, vibration theory, and thermomechanics that have been obtained with account of the relaxation properties of a medium. New equivalent analytical solutions to generalized boundary-value problems for a partially bounded domain have been obtained. The presented relations can be used for constructing mathematical models of diverse external actions on materials
Author: É. M. Kartashov
Keywords: nonstandard operational images, generalized boundary-value problems, hyperbolic-type equations, equivalent analytical solutions
THERMAL STATE OF A POLYMER DIELECTRIC LAYER WITH DIELECTRIC CHARACTERISTICS THAT DEPEND SIGNIFICANTLY ON TEMPERATURE
Based on a constructed mathematical model that describes, at alternating voltage, the steady thermal state of a plane homogeneous layer of a polymer dielectric with a nonmonotonous dependence of dielectric properties on temperature, an integral relation has been obtained that accounts for nonuniform distribution of electric fi eld strength over the layer thickness and for possible change of the thermal conductivity of a dielectric with temperature. A quantitative analysis has been made of the integral relation, intervals have been established that correspond to the existence of stable temperature distribution in the dielectric layer, and a condition was determined under which a state of thermal breakdown of the dielectric occurs
Author: V. S. Zarubin and G. N. Kuvyrkin
Keywords: dielectric, thermal state, mathematical model, integral relation, thermal breakdown of a dielectric
MATHEMATICAL MODELING OF CONTACT THERMAL RESISTANCE FOR ELASTOSTRAINED SOLID BODIES BY THE METHODS OF MULTIPHASE SYSTEMS MECHANICS
A new nonstationary conjugate mathematical model of thermal and stressed-strained state in loaded joints of metal elements in the presence of nonideal thermal contact has been formulated. A one-dimensional approximation of the model in a stationary case has been obtained. A numerical investigation of the approximate mathematical model has been carried out. Satisfactory agreement has been shown between the calculated values of thermal resistance of the contact of plane rough surfaces and the experiential data.
Author: O. R. Dornyak, V. M. Popov, and N. A. Anashkina
Keywords: heat conduction, contact thermal resistance, multiphase systems, mathematical modeling
MODELING THE INDUCTION HEATING OF PRESS EQUIPMENT IN AN AUTOMATIC-TEMPERATURE-CONTROL MODE
Consideration has been given to the most widespread three-dimensional formulations of a mathematical model of the process of inducing eddy currents in ferromagnetic materials. Two procedures have been proposed to calculate temperature fi elds of induction heating devices in a mode of automatic proportional-integral-differential temperature control, which makes it possible to considerably reduce the consumption of computer time with ensuring acceptable accuracy. The fi rst procedure provides for a successive conduct of electromagnetic and thermal analyses with the "scaling" of heat releases from the eddy currents at the stage of control. In the case of shortage computational resources it is possible to use the second procedure which involves a thermal model under the assumption of a uniform release of heat in the region of inductors and is only applicable for the inductors placed inside heated bodies. Using the calculation of temperature fi elds in press plates, molds, and vulcanized products as an example, the authors have shown the necessity of taking account of the period of stabilization of a temperature fi eld in developing and operating heating plates.
Author: A. O. Glebov, S. V. Karpov, S. V. Karpushkin, and E. N. Malygin
Keywords: induction heating, press equipment, eddy currents, PID controller, temperature fi eld, fi nite-element analysis
PREHEATING BOILER BLAST AIR WITH EXHAUST GASES IN COOLING THEM BELOW THE DEW POINT
It has been suggested that, before being fed into the boiler′s air heater, blast air be preheated in a condensation surface heat exchanger with natural combustion products cooled below the dew point. A thermal calculation has been made of a condensation heat exchanger installed behind a BKZ-420-140 NGM power boiler, which has made it possible to determine for different values of the temperature of ambient air: the heating power of the heat exchanger, the consumption of exhaust gases for preheating boiler blast air provided they are cooled below the dew point, the share of exhaust gases delivered to the heat exchanger, consumption of the steam condensate from gas fuel combustion products, the temperature, moisture content, and dew point of the exhaust gases on exit from the boiler unit, the increase in the boiler′s combustion effi ciency due to the work of the condensation heat exchanger, the coeffi cient of heat transfer from the gases to the wall and from the wall to the air being heated, and the heat-exchange coeffi cient. It has been established that the share of the exhaust gases supplied to the heat exchanger for preheating the blast air of a BKZ-420-140 NGM boiler with cooling them below the dew point, depending on the ambient air temperature, is 3.9–20.7% and 7.6–24.4% of their amount in heating the air to 20 and 30o C respectively. A calculation has been made of economic effi ciency due to preheating the blast air of the BKZ-420-140 NGM boiler at the Samara Heat and Electric Power Plant of the Samara Branch of the PJSC (Public Joint-Stock Company) "T Plus" in the condensation heat exchanger installed behind it.
Author: S. K. Ziganshina and A. A. Kudinov
Keywords: boiler, combustion products, heat exchanger, dew point, steam condensate, effi ciency
CONVECTIVE HEAT TRANSFER IN THE FLOW OF A NANOFLUID IN AN INCLINED SQUARE ENCLOSURE
The natural convective heat transfer in an inclined square enclosure fi lled with nanofl uids of different types with nanoparticles having various shapes was investigated numerically using the fi nite-element technique based on the Galerkin weighted residual. The fl ow of a nanofl uid in the enclosure was simulated with regard for the Brownian motion of the nanoparticles in the nanofl uid, the position of a uniform heat source in the enclosure, the intensity of the magnetic fi eld in it, and the orientation of this fi eld. It was established that the rate of heat transfer in the fl uid fl ow in the enclosure depends substantially on the Rayleigh and Hartmann numbers, the volume fraction of the nanoparticles in the base fl uid, the angle of inclination of the enclosure, and the position of a heat source in it. The dependence of the average rate of heat transfer in the enclosure on the position of a heat source in it and on the angle of inclination of the enclosure was calculated for the fi rst time
Author: K. S. Al-Kalbani and M. M. Rahman
Keywords: nanofl uid, natural convection, Brownian motion, heat transfer, inclined magnetic fi eld, fi nite element method
METHODOLOGICAL CHARACTERISTICS OF AN EXPERIMENTAL INVESTIGATION OF THE PROCESS OF EVAPORATION OF SUSPENDED LIQUID DROPLETS
A comparative analysis of the components of a heat fl ux occurring in evaporation of various liquid droplets suspended on fi bers from different materials (polyvinylchloride, asbestos, optical fi ber, and horsehair) blown with dry air is presented. The contribution of free convection, radiated emission, and heat transfer through a fi ber supporting an evaporating liquid droplet to an integral heat fl ux on its surface has been determined. The effect of the droplet size, the temperature and velocity of air fl ow, and the dimensions of suspension and its material on the relationships of the heat fl ux components on the droplet′s surface has been studied
Author: E. M. Bochkareva, M. K. Ley, V. V. Terekhov, and V. I. Terekhov
Keywords: liquid droplets, evaporation, heat and mass transfer, heat fl ux, forced and free convection, conductive heat fl ux, radiation heat transfer
MATHEMATICAL SIMULATION AND OPTIMIZATION OF THE CONTINUOUS DRYING OF THERMOLABILE MATERIALS
A mathematical model of the heat and mass transfer and the phase transformations in colloidal capillary-porous materials and a numerical method for calculating the dynamics of these processes in the indicated materials and the shrinkage of them in their drying in a continuous-belt drier have been developed for the purpose of optimization of the drying process. An energy-effi cient, resource-conserving convective-condensation method of drying thermolabile materials, which makes it possible to decrease the drying time, is presented.
Author: N. N. Sorokovaya, Yu. F. Snezhkin, R. A. Shapar′, and R. Ya. Sorokovoi
Keywords: mathematical simulation, continuous-belt drier, colloidal capillary-porous materials, shrinkage, thermolabile materials
FORMATION OF BI- AND POLYMODAL DISTRIBUTIONS AND THE NON-OSTWALD BEHAVIOR OF DISPERSE SYSTEMS
Consideration has been given to distinctive features of the infl uence of the chemical and phase composition of a dispersed phase, and also of external conditions on equilibrium size distributions of evaporating solution droplets containing a nonvolatile sparingly soluble component. Equilibrium radii of droplets containing a solid phase or a supersaturated solution have been described on the basis of Kelvin and Freundlich equations and Raoult′s law. Conditions have been shown under which the non-Ostwald behavior of the dispersed phase (mass transfer from large drops to small droplets) develops. Using the model distribution as an example, the possibility of the unimodal distribution transforming into a polymodal one has been demonstrated. A maximum separation of the fractions in the distribution is attained if the partial pressure of a volatile component exceeds the pressure of a vapor above a saturated solution.
Author: V. B. Fedoseev and E. N. Fedoseeva
Keywords: disperse system, aerosol, mist, size distribution, supersaturated solution, dimensional effect, evaporation, crystallization
SEPARATION OF DROPLETS IN THE FIELD OF A BOUNDARY LAYER
The movement of a small droplet in the boundary layer of the liquid–vapor fl ow in a horizontal channel with large velocity gradients is considered. The infl uence of the Magnus and Saffman lift forces on this droplet and the distance of its separation from the channel wall was investigated. The velocity components of the droplet and its reach distance were determined from the numerical solution of the system of nonlinear differential equations with the use of the Mathcad program
Author: O. Dolna and J. Mikielewicz
Keywords: droplet, separation, Magnus and Saffman lift forces
ON FILTRATION OF WATER IN A SCREENED RECTANGULAR BARRIER IN THE PRESENCE OF EVAPORATION FROM THE FREE WATER SURFACE
Plane steady-state fi ltration of groundwater in a rectangular barrier with a partially impermeable vertical wall in a bed in the presence of evaporation from the free water surface is considered. To study water fl ow by PolubarinovaKochina′s method, a mixed multiparametric boundary-value problem of the theory of analytical functions has been formulated and solved. Based on the results of the solution of this problem, an algorithm of calculating fi ltration characteristics of water fl ow through the indicated barrier has been developed, and an analysis of the effect exerted by the physical parameters of the system on the hydrodynamic fl ow pattern has been made
Author: É. N. Bereslavskii and L. M. Dudina
Keywords: fi ltration, groundwater, barrier, screen, free surface, evaporation, conformal mappings, PolubarinovaKochina′s method
NUMERICAL MODELING OF THE WATER–GAS STIMULATION OF A GAS–CONDENSATE STRATUM IN THE FINAL STAGE OF DEVELOPMENT
On the basis of a three-phase multicomponent model of fi ltration of fl uids, the authors have modeled the displacement of a gas–condensate mixture by water with addition of a gas phase with account taken of all the physiochemical processes. A study has been made of the possibilities of raising the condensate recovery ratio at the fi nal stage of development with water–gas stimulation
Author: Kh. A. Feizullaeva and M. S. Khalilovb
Keywords: pressure, fl uid, phase-state equation, thermodynamic equilibrium, gas–condensate mixture, water–gas stimulation
TOWARDS THE THEORY OF WASHING-OUT SALT FROM WATER–OIL EMULSIONS
The fl ow of oil containing admixtures of mineralized water droplets and meeting the counterfl owing fresh water droplets of larger radius in the working zone of the mixing chamber of a jet hydraulic mixer is investigated. A mathematical model of coalescence of the mineralized and fresh water droplets has been developed. Based on empirical data, estimates of the hydrodynamic parameters of such a fl ow have been performed. Assumptions are made that mineralized and fresh water droplets are spherical particles, whose coagulation (coalescence) takes place when the trajectory of the mineralized water droplet crosses the fresh water droplet boundary. Calculation results are presented illustrating the infl uence of the radius and velocity of a fresh water droplet and also of oil velocity on the process of coalescence of these droplets
Author: V. Sh. Shagapov, É. V. Galiakbarova, and I. K. Gimaltdinov
Keywords: particle motion, inertia, adhesion, coagulation
ENERGY-EFFICIENT MODES OF DRYING OF COLLOIDAL CAPILLARY-POROUS MATERIALS
Drying is one effi cient technological method to preserve and process vegetable raw material. This is a thermotechnical process with a high expenditure of the energy carrier, which is accompanied by irreversible phenomena. Therefore, it is of fi rst importance to carry out investigations on selecting an optimum drying mode to ensure a maximum expenditure of the energy carrier and a maximum rate of removal of moisture, and also to retain all the physicomechanical and biochemical properties of the dried material
Author: Zh. A. Petrova and E. S. Slobodyanyuk
Keywords: drying, heat technology, carotenoids, phytoestrogens, rate of drying
EXPERIMENTAL INVESTIGATION OF MAGNETIC PARTICLE TRANSPORT IN A CIRCULAR MINICHANNEL IN A CONSTANT MAGNETIC FIELD
Experimental investigation of the deposition of nanoparticles in a circular channel in a constant magnetic fi eld has been carried out. The dynamics of growth of nanoparticles deposits on the channel walls depending on the Reynolds number and magnetic fi eld strength has been studied in the experiments. The infl uence of magnetic fi eld on pressure drop at different Reynolds numbers has been investigated. Characteristic profi les of the zones of nanoparticles depositions have been obtained for the fi rst time; the sizes of the deposition areas and the rates of their formation depending on the Reynolds numbers, magnetic fi eld strength and time have been determined
Author: A. V. Minakov, D. V. Guzei, V. A. Zhigarev, M. I. Pryazhnikov, and A. A. Shebeleva
Keywords: magnetic nanoparticles, magnetic separation, pressure drop, targeting delivery, nanoparticle transport, magnetic field
GROWING OF CARBON NANOTUBES FROM HYDROCARBONS IN AN ARC PLASMA
A new method of synthesis of multilayer carbon nanotubes from liquid hydrocarbons is proposed. The interaction of an electric arc, fi ring between an anode and a cathode submerged in a thick layer of a heavy-hydrocarbon liquid, with hydrocarbon molecules was investigated for the purpose of obtaining new light fractions of oil and an atomic carbon. The carbonaceous substance deposited on the cathode was analyzed on an electron microscope. Chromatographic investigations of the products of the plasmachemical decomposition of heavy hydrocarbons have been performed. It was established that carbon nanotubes are present in a large amount in the deposit on the cathode and that the volatile oil fractions include gasoline fractions, acetylene, methane, ethane, and other substanc
Author: B. A. Timerkaev, G. R. Ganieva, A. A. Kaleeva, Z. Kh. Israfilov, and A. O. Sofronitskii
Keywords: arc discharge, submerged arc, plasma chemistry, liquid hydrocarbon material, multilayer carbon nanotubes
USE OF NANOPARTICLES OF A FINELY DISPERSED SILICON CARBIDE OBTAINED IN AN ELECTROTHERMAL BOILING BED AS A STRUCTURAL MODIFIER OF THERMOPLASTIC POLYMERS
Porous powders of a fi nely dispersed silicon carbide obtained as a result of the carbothermal reduction of silica in an electrothermal boiling-bed reactor were investigated. It was established that such a powder comprises siliconcarbide nanoparticles of size ~50–70 nm and fi lametry formations of these nanoparticles with an aspect ratio of ~5–15. It is shown that the silicon-carbide nanoparticles introduced in a thermoplastic polymer interact with its matrix and, in so doing, change the polymer structure, with the result that a composite material is formed. Such thermoplastic polymer composites possess enhanced physical, mechanical thermal, and thermophysical properties. New heat-conducting polymer composite materials having a high wear resistance and good antifriction properties have been developed. These materials can be used in machine building as protective coatings, members, and units of facilities operating in the regime of abrasive wear, in power and electrical engineering, and in microelectronics where there is a need for heat-conducting thermoplastic polymer materials
Author: V. I. Dubkova, V. A. Borodulya, L. M. Vinogradov, S. M. Danilova-Tret′yak, L. E. Evseeva, and T. I. Pinchuk
Keywords: fi nely dispersed silicon carbide, silicon-carbide nanoparticles, composite materials, physiochemical interaction, structure, properties
THERMAL PROPERTIES OF COMPOSITE MATERIALS BASED ON THE POWDER SYSTEMS "COPPER–CNTs"
The infl uence of the metal matrix fi lling with carbon nanotubes on the thermal properties of copper-based powder composite materials has been studied. It has been revealed that the powder systems ″copper–CNTs″ obtained according to the powder-metallurgy technology by electric-contact sintering possess anisotropic thermal conductivity under certain conditions. It has been found that during uniaxial molding, in the process of electric-contact sintering, CNTs are oriented in one direction, which leads to a rise in the values of the thermal-conductivity coeffi cient in this direction. It has been established that at a CNT concentration below the percolation threshold, experimental values of the thermal-conductivity coeffi cient of the composite materials are in good correlation with the values obtained with the Maxwell–Garnett theoretical model. It was noted for the fi rst time that the Maxwell–Garnett theoretical model can be used to assess the distribution of a nanosize fi ller in a metal matrix.
Author: V. N. Pasovets, V. A. Kovtun, M. Mihovski, and Yu. M. Pleskachevskii
Keywords: power metallurgy, electric-contact sintering, composite materials, carbon nanotubes, thermalconductivity coeffi cient
INFLUENCE OF THE HIGH-TEMPERATURE EFFECTS IN A NOZZLE WITH A NONSTATIONARY LOCAL POWER SUPPLY ON THE GAS FLOW IN IT
A simulation of a high-temperature air fl ow in a nozzle with a nonstationary local power supply has been performed. The thermodynamic processes in this fl ow were simulated using an approximate model of equilibrium air thermodynamics. Results of a numerical simulation of one-dimensional fl ows in nozzles with a moving powersupply zone, used in alternating-current plasma generators, are presented. On the basis of the numerical-simulation data obtained, the qualitative patterns of the gasdynamic and thermal processes proceeding in such a nozzle with a nonstationary power supply were analyzed. The results of calculations performed on the basis of the ideal-gas and real-gas models with regard for the physicochemical processes occurring in a real gas at a high temperature were compared
Author: N. A. Brykov, K. N. Volkov, V. N. Emel′yanov, and I. V. Teterina
Keywords: nozzle, plasma generator, power supply, computational gas dynamics, fi nite-volume method, gas-fl ow rate, compression shock
VELOCITY FIELD OF GAS FLOW IN THE EXTERNAL WAVE FIELD NEAR AN OPEN END OF A TUBE IN TRANSITION THROUGH A RESONANCE FREQUENCY
The velocity fi eld of gas fl ow fi eld has been studied under forced longitudinal oscillations of homogeneous gas in an open tube near the fi rst natural frequency. Dependences of gas velocity in the axial direction in the external wave fi eld at different distances from the open end of the tube have been obtained. Experimental results have been compared to theoretical calculations.
Author: R. G. Zaripov, L. A. Tkachenko, and L. R. Shaidullin
Keywords: forced longitudinal oscillations, resonance, velocity, external wave fi eld.
TAYLOR INSTABILITY OF MAGNETIC LIQUID FLOW IN AN AXIAL MAGNETIC FIELD
The results of investigation of the Taylor instability of magnetic liquid fl ow in a homogeneous magnetic fi eld between rotating cylinders in the narrow gap approximation are presented. It has been established that the nonisothermicity of fl ow leads to a substantial decrease in the instability threshold, as in an ordinary liquid. On the other hand, the infl uence of the magnetic fi eld is reduced to the instability threshold of an ordinary liquid by means of viscosity renormalization, i.e., the redetermination of viscosity in terms of anisotropic components. Apart from the results obtained, the work is of interest in the context of the methods of numerical solution of such class of problems.
Author: V. A. Novikov
Keywords: magnetic liquid, Taylor vortices, Reynolds number, Prandtl number, Brinkman parameter, rotational viscosity, narrow gap, Newton method, Hemming method
ON HYPERBOLIZATION OF A NUMBER OF CONTINUUM MECHANICS MODELS
By using the Maxwell–Cattaneo approach, the equations of motion of a viscous heat conducting gas and of a heterogeneous medium are hyperbolized in one- and multivelocity approximations with relaxation laws of viscosity and thermal conductivity. The modifi ed Godunov method with a linearized Riemann solver intended for integration of nondivergent systems is described.
Author: V. S. Surov
Keywords: one- and multivelocity multicomponent mixtures, relaxation viscosity and thermal conductivity, hyperbolic systems of equations, Godunov′s method
NUMERICAL STUDY OF ELECTROCONVECTION IN A DIELECTRIC LAYER BETWEEN TWO COFOCAL ELLIPTICAL CYLINDERS SUBJECTED TO UNIPOLAR INJECTION
The problem of electroconvection in an annular space between two elliptical concentric cylinders fi lled with a dielectric liquid and subjected to internal unipolar injection is considered. A fi nite volume method is used to solve the governing equations, including the Navier–Stokes ones and a simplifi ed set of the Maxwell equations. For the fi rst time the whole set of these coupled equations is solved, using the elliptical-cylindrical coordinates. We fi rst validate numerical simulation in this fi eld by comparing the results obtained with those available in the literature. The numerical solution of the electroconvection problem is then followed by a detailed analysis of the fl ow structure and electric charge distribution. It is shown that the multicellular convective pattern is observed. It is noticed that unipolar charge injection from the internal electrode signifi cantly changes the topology of the fl uid fl ow. Finally, the infl uence of various system parameters, such as the injection level and electric Rayleigh number, is also investigated.
Author: M. I. Elkhazen, W. Hassen, R. Gannoun, A. K. Hussein, and M. N. Borjini
Keywords: electroconvection, elliptical cylinders, dielectric liquid, numerical simulation
SIMULATION OF HYDRODYNAMICS AND HEAT TRANSFER OF A GRANULATED MEDIUM IN A CIRCULAR BUNKER
Numerical simulation of the hydrodynamics and heat transfer of a dense layer of a highly loose high-concentration granulated medium in a circular bunker on the basis of a non-Newtonian medium with application of the ″power-law liquid″ model and boundary slipping conditions on solid walls is presented. The infl uence of regime and geometric parameters on the dynamics and heat transfer of a high-concentration granulated medium is investigated. The validity of the results obtained is confi rmed by comparison of the numerical results with well-known experimental and analytical data. The results of the investigation carried out can be used in powder technology apparatuses in the processes of drying, mixing, homogenization, batching, and transportation of granulated materials.
Author: A. V. Shvab and E. A. D′yakov
Keywords: rheology, granulated medium, power-law model, circular bunker, slipping conditions, stress tensor
MATHEMATICAL MODEL AND CALCULATION OF THE RATE OF COMBUSTION OF A FROZEN AQUEOUS SUSPENSION OF A NANODISPERSE ALUMINUM
A mathematical model of combustion of a frozen aqueous suspension of a nanodisperse aluminum, making possible the determination of the parameters of this process with account of the dependence of the specifi c heat, evaporation heat, and boiling point of water on the pressure at the vaporization surface of the suspension without the predetermination of the ignition temperature of aluminum particles, is presented
Author: A. Yu. Krainov and V. A. Poryazov
Keywords: frozen aqueous suspension, nanodisperse aluminum, combustion, mathematical simulation
INFLUENCE OF THE TREATMENT OF SURFACES OF MATERIALS IN A DIELECTRIC-BARRIER-DISCHARGE PLASMA ON THEIR MORPHOLOGY AND HYDROPHILIC PROPERTIES
Investigations of the morphology of surfaces of glass, titanium, and polymer fi lms in the initial state and after treatment in the plasma of a dielectric barrier discharge by atomic force microscopy have been carried out. The change in the topography of these materials′ surface and in its roughness and hydrophilic-hydrophobic properties has been established after the treatment in the dielectric-barrier-discharge plasma.
Author: V. A. Lapitskaya, T. A. Kuznetsova, A. A. Rogachev, G. B. Mel′nikova,a S. A. Chizhik, and D. A. Kotov
Keywords: plasma, dielectric barrier discharge, surface, hydrophilic-hydrophobic properties, atomic force microscopy, roughness
THERMOPHYSICAL AND THERMOKINETIC CHARACTERISTICS OF FOREST COMBUSTIBLE MATERIALS
Experiments on determination of main thermophysical parameters (heat conductivity, heat capacity, thermal diffusivity) and thermokinetic characteristics (activation energy of pyrolysis and fl aming) of typical forest combustible materials and their mixtures, taken from the Siberian, Central, Southern, and Far Eastern Federal Districts of Russia, have been performed in the wide temperature range 298–423 K corresponding to the initiation of thermal decomposition and subsequent fl aming of forest combustible materials. Results of these experiments were compared with experimental data obtained by other researchers. A database, which can be used in the mathematical simulation of the thermal decomposition and fl aming of forest combustible materials as well as in the determination of conditions necessary for the localization and suppression of a forest fi re, has been developed.
Author: A. O. Zhdanova, S. S. Kralinova, G. V. Kuznetsov, and P. A. Strizhak
Keywords: forest combustible material, thermophysical and thermokinetic characteristics, thermal decomposition, oxidation, fl aming
INFLUENCE OF ULTRASONIC FIELD ON KINETIC COEFFICIENTS IN THE PROCESS OF EXTRACTION
Quantitative estimate of the effect of an ultrasonic fi eld on kinetic coeffi cients in the process of extraction of a technological pollution from a typical cotton cloth of mean density is presented. It has been established that the kinetic coeffi cients of mass transfer and of mass conductivity increase on exposure of a fl ushing solution to ultrasound. The results obtained can be applied in kinetic calculations of the process of fl ushing cotton fabrics of mean density.
Author: M. K. Kosheleva and S. P. Rudobashta
Keywords: extraction, ultrasonic fi eld, chemical technology of fi nishing, kinetics, fi brous material, mass conductivity, mass transfer
NONDESTRUCTIVE CONTROL OF DIFFUSIVITY IN UNIAXIALLY REINFORCED POROUS-MATERIAL PRODUCTS
A modifi cation is considered of the pulse method of nondestructive control of diffusivity to ensure the possibility of its use to investigate uniaxially reinforced porous material products that are characterized by signifi cant anisotropy of properties. Results are presented of the selection of design parameters of a measuring device and operating conditions of the process of measuring the required diffusivity that ensure an increase in the effi ciency and accuracy of the applied method of nondestructive control.
Author: V. P. Belyaev, S. V. Mishchenko, and P. S. Belyaev
Keywords: nondestructive control, uniaxially reinforced products, porous material, diffusivity, anisotropy