Volume 94, №4
SYNTHESIS OF HEAT-EXCHANGE SYSTEMS WITH FLOWS OF VARIABLE HEAT CAPACITY INTEGRATED IN A TECHNOLOGICAL PROCESS
The conditions of minimum entropy production in a two-fl ow heat exchanger, in which one of the contacting fl ows
has a defi nite temperature, were determined. The simplifi cation of a heat-exchange system with fl ows whose heat
capacity depends on their temperature was considered for the particular case where one of these fl ows changes its
phase state. The thermodynamic equivalence of two-fl ow and multifl ow heat transfer processes was investigated. An
algorithm is proposed for the synthesis of a heat-exchange system, integrated in a technological process, in which
the temperature and heat capacity of all the fl ows or some of them are fi xed and which has a minimum surface of
contact interaction of the fl ows in it. It is shown that this algorithm holds for a heat transfer process of any kinetics
Author:
A. M. Tsirlin, A. I. Balunov, and L. G. Gagarina
Keywords:
multifl ow heat exchange, irreversibility, minimum heat dissipation, thermodynamic equivalence, heat load, integrated systems
Page:
813
OBTAINING ISOTOPICALLY MODIFIED MOLYBDENUM IN ORDINARY AND DOUBLE CASCADES OF GAS CENTRIFUGES
A method has been developed for calculating the parameters of cascades with an assigned number of gas centrifuges in the stages whose separation factors depend on their feed fl ow and the fl ow cut. Based on this method, a computational experiment was conducted on separation of molybdenum hexafl uoride and concentration of 92,98,100Mo isotopes with a low neutron-capture cross section in the outgoing streams of ordinary and double
cascades. The author has determined the features of obtaining isotopically modifi ed molybdenum from waste and
selected products of such cascades, which is suitable for creating reactor materials with improved thermophysical
characteristics. The infl uence of the factors associated with the feed fl ow of cascades and the types of stages, as
far as the number of gas centrifuges is concerned, has been studied. It has been shown that the feed fl ows and the
separation factors of the stages of gas-centrifuge cascades differ signifi cantly from rectangular and rectangularpartitioned cascades.
Author:
V. A. Palkin
Keywords:
separation of isotopes, molybdenum isotopes, separation cascade, gas centrifuge, separation factor
Page:
829
MACROSCOPIC PRESSURE FILTRATION FIELD IN A MEDIUM WITH DOUBLE POROSITY
This article presents a mathematical model of the pressure fi ltration fi eld in a porous medium with a skeleton formed
by two solid phases of identical elemental composition but differing by porosity and permeability, in which the pore
space of solid phases is fi lled by a homogeneous fi ltering liquid. Based on the continuity equations for each of the
phases, equations have been found for the pressure fi eld, and it was shown that the macroscopic averaged fi eld is
described by a nonlinear equation which in the case of a weakly compressible moving phase is reduced to the equation
of piezoconductivity with an effective compressibility parameter. Based on the asymptotic method, expressions have
been constructed for the zero and fi rst coeffi cients of expansion of a nonlinear problem on macroscopic pressure
fi ltration fi eld in the case of one-dimensional axisymmetric radial fi ltration in an oil-bearing gassy bed. An approach
is suggested establishing the correspondence between the pressure fi elds for the linear and radial fl ows. Results of
calculations by the obtained analytical dependences and fi nite-difference algorithms are presented, and the ideas
about the dynamics of the pressure fi ltration fi elds are refi ned
Author:
A. I. Filippov, A. A. Koval′skii, O. V. Akhmetova, M. A. Zelenova, and M. R. Gubaidullin
Keywords:
fi ltration, double porosity, asymptotic expansion, fi nite-difference algorithm, nonlinear piezoconductivity equation
Page:
837
PROPAGATION OF SUBSTANCE IN AN AXISYMMETRIC FILTRATION FLOW
The article considers the propagation of a substance in a cylindrical coordinate system in fi ltration fl ow. A common
assumption is made that the dispersion coeffi cient is proportional to the transport velocity. Examples of exact
solutions have been obtained supplemented with asymptotic representations. The possibility of using simple
expressions to approximate a two-dimensional surface (a series of curves) that refl ects the solution of the problem
is demonstrated.
Author:
A. I. Moshinskii
Keywords:
fi ltration, convective transfer, porous body, fl ow of matter, approximation
Page:
849
SIMULATION OF THERMAL PROCESSES IN A WELL WITH A MULTIBED SYSTEM IN THE EXTRACTION OF LIVE CRUDE
Based on the numerical model describing the nonisothermal motion of a two-phase fl uid in a well with a multibed
system, the problem of the takeoff of a live crude from a well operating on two reservoir beds with the temperature
fi eld formed under the action of the adiabatic effect, Joule–Thomson effect, and of the crude degassing heat, is
considered. The characteristic features of temperature effects in a dual completion well with variation of the Henry
solubility coeffi cient and of the permeability of some of the reservoir beds are considered
Author:
I. V. Kanafi n, R. F. Sharafutdinov, and T. R. Khabirov
Keywords:
thermometry, two-phase fl ow, degassing of oil, degassing heat, well, reservoir bed, multibed system
Page:
860
PROCEDURE FOR PREDICTING THE INDICES OF DEVELOPMENT OF DEEP-SEATED GAS–CONDENSATE RESERVOIRS IN A DEPLETION REGIME FROM WELLHEAD DATA
By simultaneous solution of the equation of infl ow of a gas–condensate mixture in the formation and in the tube and
with account taken of the phase states of the gas–condensate mixture, the author has implemented a calculation
procedure that makes it possible to predict, from wellhead data, the pressure at the wellbore and the formation
pressure, and also other technological indices of development of deep-seated gas–condensate reservoirs in a
depletion regime. Within the limits of the considered initial data, the author has modeled the process of infl ow
of the gas–condensate mixture to a partially penetrating well in a homogeneous anisotropic formation and has
established the regularities of infl uence of the site of drilling-in and the degree of imperfection of the accumulation
of a retrograde condensate in near-wellbore zones with time.
Author:
M. S. Khalilov
Keywords:
depletion regime, homogeneous anisotropic formation, retrograde condensate, partially penetrating well, phase state of a gas–condensate mixture
Page:
870
SIMULATION OF THE INJECTION OF LIQUID CARBON DIOXIDE INTO A GAS-HYDRATE STRATUM OF FINITE EXTENT
Results of numerical investigation of the injection of liquid carbon dioxide into a porous stratum saturated with
methane and its gas hydrate, accompanied by the replacement of methane in the methane gas hydrate by carbon
dioxide, are presented. A round stratum with an impermeable outer boundary of fi nite radius was considered. It
was established that, depending on the duration of the injection of liquid carbon dioxide into such a stratum, the
replacement of methane in the methane gas hydrate by carbon dioxide can proceed with the boiling of carbon dioxide
or without it
Author:
M. K. Khasanova and M. V. Stolpovskii
Keywords:
hydrates, replacement, carbon dioxide, methane
Page:
883
ON A SOLUTION TO THE EQUATION OF FILTRATION OF A LIQUID IN A PERMEABLE MEDIUM
The authors consider nonstationary fl ow of a gas from a screen vacuum thermal insulation into vacuum and discuss
its coupling to the Boussinesq solution of the classical problem on fi ltration of a liquid in a porous medium. A
nonlinear one-dimensional fi ltration equation has been solved numerically, and it has been shown that the outfl ow
from a porous body uniformly fi lled with the gas occurs in two stages. The fi rst stage involves the formation of selfsimilar fl ow, and the second is fully described by the Boussinesq solution
Author:
V. A. Nevrovskii and V. A. Shishkin
Keywords:
porous body, fi ltration equation, screen vacuum insulation, Boussinesq solution, self-similar flow
Page:
892
MACROKINETIC MODELS OF THERMAL DECOMPOSITION OF DOLOMITE FOR ENGINEERING CALCULATIONS
The authors have formulated macrokinetic models of thermal decomposition of dolomite that vary in the number
of the considered effective chemical processes, the mechanism of evacuation of carbon dioxide, the dependent/
independent behavior of chemical reactions, and the number of parameters. The models were used as basic ones
for approximating experimental data on the thermal decomposition of dolomite. The experiments on dolomite
decomposition were conducted with a Q-1000 derivatograph of the MOM Company at a rate of heating of the
samples of 5, 10, and 20 K/min, and also in a quasi-thermal regime. Based on the array of experimental data, the
authors have determined the parameters of dolomite-decomposition models. An analysis of the adequacy of the
models to the experimental data has been made. It has been shown that taking account of the series character of
decomposition of dolomite and calcite in two reactions does not result in the improvement of the approximation
accuracy of experimental data. The approximation accuracy of experimental data corresponds to the accuracy of
approximated experimental data, with the models with 5 to 7 parameters exhibiting no noticeable advantages over
3- and 4-parametric models. However, the model with 2 parameters shows much lower accuracy. The models whose
parameters were set according to the dynamic dolomite-decomposition data satisfactorily describe quasi-isothermal
decomposition regime too; however, in modeling the latter, it is expedient to set the model′s parameters according to
the data of quasi-isothermal experiments.
Author:
K. V. Dobrego, I. A. Koznacheev, E. S. Shmelev, M. V. Mal′ko, and S. V. Vasilevich
Keywords:
dolomite, kinetics, thermogravimetry, modeling
A MODEL OF POLYDISPERSE VAPOR–DROPLET MIXTURE FLOW IN A VORTEX CHAMBER
A thermo- and hydrodynamic model of polydisperse vapor–droplet mixture fl ow in a vortex evaporation chamber
has been described. The motion of the mixture can be accompanied by fragmentation, coagulation, and evaporation
of droplets and by vapor condensation. The model involves the system of equations of motion of the carrying
medium and the systems of the equations of motion of a number of disperse fractions. To describe the motion of
the carrying medium a system of equations of motion of a viscous compressible heat-conducting gas is used with
account for the mass, momentum, and energy exchange with the despersed phase fractions. The disperse dropping
liquid fractions are described by systems of equations of gas-dynamic type with account for interphase exchange
by mass, momentum, and energy with the carrying medium. The system of equations of the vapor–droplet mixture
is represented in generalized curvilinear coordinates and is solved by explicit McCormack's method with splitting
of the spatial operator in directions and with the scheme of nonlinear correction at each time step. The model is
supplemented by the mechanisms of fragmentation, coagulation, evaporation of droplets and vapor condensation
with subsequent correction of hydro- and thermodynamic parameters of the mixture. Based on the model presented,
the fl ow of polydisperse single-component vapor–droplet methane mixture in a vortex evaporation chamber has been
calculated.
Author:
A. L. Tukmakov and N. A. Tukmakova
Keywords:
vapor–droplet mixture, carrying medium, polydispersity, fractions of droplets, Navier–Stokes equations, McCormack′s explicit scheme, fragmentation coagulation, evaporation, condensation
Page:
910
ROLE OF VISCOSITY AND TEMPERATURE FACTORS IN THE MAGNETOPHORESIS OF DISPERSED PHASE OF DIFFERENT LIQUID MEDIA
The role of rheological properties of a liquid dispersion medium, in particular, its dynamic viscosity determined by
the temperature of the medium, in its magnetophoretic separation was investigated. The temperature dependences
of the viscosity of a water and other liquids as well as their phenomenological approximations by logarithmic,
exponential, and power functions in the working temperature ranges of these liquids are presented. The defi nition
of the effi ciency of separation of a liquid dispersion medium with the use of magnetic fi lters by one of the indicated
functions (a logarithmic one) and its testing by the corresponding experimental temperature dependence obtained
for a low-concentration aqueous suspension, whose continuous medium is a water or an industrial condensate and
disperse phase is formed by particles of a synthetic magnetite or ferroparticles, are considered.
Author:
A. V. Sandulyak, D. A. Sandulyak, M. N. Polismakova, A. A. Sandulyak, and V. A. Ershova
Keywords:
magnetophoretic drift, particles, Stokes force, dynamic viscosity, separation, temperature
Page:
919
ON STARTUP OF A BOILER WITH A LOW-POWER FLUIDIZED BED
An investigation has been made into the process of heating up the granular bed in two regimes: heating up a roomtemperature fl uidized bed and heating it in conditions of thermal fl uidization
Author:
Yu. S. Teplitskii, E. A. Pitsukha, A. R. Roslik, and É. K. Buchilko
Keywords:
fi xed granular bed, fl uidized bed, burning waste wood bed, boiler startup
Page:
927
HYDROMAGNETIC NATURAL CONVECTION FROM A HORIZONTAL POROUS ANNULUS WITH HEAT GENERATION OR ABSORPTION
This paper deals with a numerical study of free convection in a horizontal cylindrical annulus fi lled with a fl uidsaturated porous medium in the presence of a transverse magnetic fi eld and the heat generation or absorption effect.
It is assumed that the inner and outer walls of the cylindrical annulus are maintained at constant temperatures Ti
and To , respectively, as Ti > To . In addition to the heat equation, the model consists of the equation of motion under
the Darcy law and Boussinesq approximation. The system of equations is solved numerically by the alternatingdirection implicit fi nite difference method. This investigation concerns the effects of the magnetic fi eld inclination
angle, Hartmann number, and the heat generation or absorption coeffi cient on heat transfer and the fl ow pattern.
The results demonstrate that the heat transfer rate and fl ow regime depend mainly on the characteristics mentioned.
The obtained data are presented graphically in terms of the streamlines and isotherms
Author:
J. Belabid
Keywords:
free convection, inclined magnetic fi eld, heat generation/absorption, heat transfer, porous medium
Page:
934
MICROSTRUCTURE OF THIN FILMS OF TANTALUM AND ITS COMPOUNDS
By the atomic-force-microscopy method, the authors have studied the microstructure of coatings from tantalum
and its compounds, which were formed on the surface of substrates from stainless steel and microscope slide by
reactive magnetron sputtering. It has been established that nanostructured tantalum fi lms are characterized by
the cellular structure the size of whose cells depends on the material and the physicochemical properties of the
substrate surface
Author:
A. S. Petrovskaya, V. A. Lapitskaya, G. B. Mel′nikova, T. A. Kuznetsova, S. A. Chizhik, A. V. Zykova, and V. I. Safonov
Keywords:
tantalum fi lm, magnetron sputtering, atomic-force microscopy, microstructure, roughness
Page:
942
MATHEMATICAL SIMULATION OF IGNITION OF AN ORGANIC COAL–WATER FUEL DROPLET
A mathematical model affording satisfactory representation of experimental values for the characteristics of the
ignition of organic coal–water fuel droplets has been developed. Numerical investigations of the processes of
ignition of droplets of the fuels based on typical wastes from dressing hard coals, enriching industrial oils, and
water have been carried out. The delay times in ignition of organic coal–water fuel droplets with their radii varying
from 0.25 to 1.5 mm, at oxidant fl ow velocity varying from 0.5 to 3 m/s and of its temperature varying from 700 to
1000 K, have been established. A satisfactory correspondence of the results of mathematical simulation to the familiar
experimental data has been obtained. The possibility of using the ANSYS Fluent package for numerical simulation
of the ignition of organic coal–water fuel droplets has been substantiated. The temperature fi elds of such droplets
on ignition, as well as the coordinates of the zones of their intense chemical transformations, have been calculated.
Prediction of the limiting conditions of stable ignition of organic coal–water fuels on relatively low-temperature
heating has been made.
Author:
D. V. Antonov, K. Yu. Vershinina, G. V. Kuznetsov and P. A. Strizhak
Keywords:
organic coal–water fuel, droplet, ignition delay time, mathematical simulation
Page:
949
OBTAINING HYDROGEN FLUORIDE DURING THE INTERACTION OF URANIUM HEXAFLUORIDE WITH HYDROGEN AND OXYGEN IN A COMBUSTION REGIME. THERMODYNAMIC ANALYSIS
The objective of the work was to thermodynamically substantiate the method of obtaining hydrogen fl uoride from
uranium hexafl uoride by its treatment in the fl ame of a hydrogen-containing fuel and an oxygen-containing oxidant.
It was shown by calculations that in the system of elements U–F–H–O when the number of hydrogen atoms is larger
or equal to the number of fl uorine atoms and the number of oxygen atoms is twice as large as the number of uranium
atoms, the major uranium-bearing compounds in the thermodynamically equilibrium mixture of substances at a
temperature above 1100 K are uranium oxides, and the only, in practice, fl uorine-containing compound is hydrogen
fl uoride. The indicated temperature can be reached in the case of interaction of uranium hexafl uoride with hydrogencontaining and oxygen-containing substances in a combustion regime, e.g., with hydrogen and oxygen. The obtained
results may become a basis for experimental investigation into the production of hydrogen fl uoride from uranium
hexafl uoride in a combustion regime.
Author:
D. S. Pashkevich, A. R. Zimin, V. V. Kapustin, and V. B. Petrov
Keywords:
hydrogen fl uoride, depleted uranium hexafl uoride, uranium dioxide, thermodynamic equilibrium, Gibbs energy, combustion
Page:
963
DIGITAL TWIN OF A HIGH-ENERGY SYSTEM USING ALUMINUM HYDRIDE AS A FUEL
Numerical modeling of the fl ow of combustion products of the propellant containing an aluminum hydride admixture
in the nozzle of a solid-propellant rocket engine has been carried out. The advantage of aluminum hydride over
aluminum when used in composite solid propellants has been shown.
Author:
A. B. Vorozhtsov and N. N. D′yachenko
Keywords:
two-phase fl ow, polydisperse ensemble of particles, specifi c momentum
Page:
972
SIMULATING ASSOCIATED GAS FLARING IN A RECOVERY COMBUSTION CHAMBER
Using ANSYS Fluent software, numerical simulation has been conducted for fl ow and burning processes in
combustion chambers of gas-turbine power plants designed to recover oil-associated (casing-head) gas. The working
process equations are considered in the Euler approach. The system of partial differential equations describing a threedimensional burning turbulent fl ow contains the laws of conservation of total mass, the mass of separate combustion
product components, the combustion product momentum, the combustion product energy, the law of conservation of
fuel composition elements, mixture fraction, turbulence kinetic energy. and dissipation of turbulence kinetic energy. The
introduction of mixture fraction simplifi es substantially the solution of the problem of turbulent mixing of the oxidizing
agent and the fuel. Scalar quantities (density, temperature, and mass concentrations of components) are determined
using the probability density function in accounting for the fi nal chemical reaction rate of an unpremixed mixture. The
fl ow velocity fi eld is calculated using the "realizable" k–ε turbulence model. The results have been obtained for different
schemes of component supply into the combustion chamber. A comparison of calculated and experimental data is given
Author:
N. L. Bachev, O. O. Matyunin, A. A. Shilova, R. V. Bul′bovich
Keywords:
numerical simulation, working process equations, hybrid model, verifi cation of results
Page:
977
EXPERIMENTAL INVESTIGATIONS OF A GAS BURNER WITH A HEAT-TRANSFER INTENSIFIER IN THE FORM OF A ROD WITH TAPERED-SCREW FINS
Experimental investigations of a new burner for gas ranges have been conducted. We present a modifi ed construction
diagram of a burner with a new heat-transfer intensifi er in the form of tapered-screw fi ns on the surface of a metal
rod that has shown its effi ciency and made it possible to raise the cost effectiveness of natural gas combustion
compared to a base burner
Author:
K. V. Altunina, F. A. Kadyamov
Keywords:
natural gas, gas burner, heat-transfer intensifi er
Page:
986
MODELING AND IMPLEMENTATION OF ELECTROCONTACT WELDING DEPOSITION OF POWDERS OF SELF-FLUXING ALLOYS
An analysis of the regularities of electrocontact welding deposition of powders of self-fl uxing alloys has been made. A model and an implementation technology for this process have been developed. Results of metallographic investigations and tribotechnical tests of the obtained coatings have been given. The adequacy of the developed model has been shown when using it in calculations of the regimes of electrocontact welding deposition of powder materials. It has been established that the structures of the obtained coatings correspond to the structures of wearresistant antifriction coatings produced from melts with an initial temperature no more than 50–100o C higher than
the melting point of the material of powder particles. Crystallization of these melts under forging conditions ensures
the formation of fi ne graininess in the materials of coatings obtained from them, with the grains having somewhat
smeared boundaries within which the hereditary structure of the material of the original powder may be preserved
Author:
O. O. Kuznechik,a E. G. Grigor′ev, A. V. Sosnovskii
Keywords:
electric-current sintering, metallographic investigations, tribotechnical tests, electrocontact welding deposition, self-fl uxing alloys
Page:
995
HYBRID APPROACH TO MODELING THE PROCESS OF CONVECTIVE RADIATIVE HEAT AND MASS TRANSFER IN CLOSED DIFFERENTIALLY HEATED CAVITIES
A hybrid model has been developed for the analysis of the process of combined mass and heat transfer in closed
rectangular cavities under the conditions of volumetric radiation of a medium. Within the framework of the
formulated method, hydrodynamics is described by the mesoscopic lattice Boltzmann method, and the macroscopic
equations of energy and concentration are described by the method of fi nite differences. To calculate the radiation
fl ux, use was made of approximation of an optically thick layer. Based on the results of mathematical modeling,
it has been established that accounting for radiation heat transfer results in an increase of the incidence angle of
thermal stratifi cation and the formation of external secondary fl ows. The convective Nusselt number decreases as the
radiation parameter rises. On the other hand, it has little effect on the mass transfer rate
Author:
A. É. Nee
Keywords:
lattice Boltzmann equations, hybrid model, method of fi nite differences, Rosseland model, natural convection
Page:
1008
CALCULATION OF THE PRESSURE PULSATIONS IN AN EXPANSION JOINT OF A PIPELINE THROUGH WHICH A LIQUID IS PASSED
The pressure pulsations in a working liquid fl owing through an expansion joint of a pipeline in a power installation
were calculated. The vibration of the path of such an installation and the nonstationary fl ow of a compressible
liquid in it were simulated with the use of original methods of the computational fl uid dynamics and moving meshes.
The calculation data obtained are in good agreement with the corresponding results of a natural experiment and
numerical predictions made on the basis of a simplifi ed analytical model.
Author:
A. V. Kiryukhin, O. O. Mil′man, S. A. Isaev, A. V. Minakov, A. B. Shebelev
Keywords:
vibration, vibrational stiffness, dynamic force, pressure pulsations, numerical simulation, experiment
Page:
1020
COMPUTATION OF COMPRESSIBLE GAS FLOW USING GENERAL-PURPOSE GRAPHICS PROCESSING UNIT
Possibilities for using general-purpose graphics processing units to simulate compressible gas fl ows are discussed.
Consideration is given to different schemes of computation of fl ows through the faces of the fl ow control volume and
to the features of their implementation on graphics processing units. A solution of a number of model problems of
gas dynamics on graphics processing units is presented and consideration is given to approaches to optimization of
the program code connected with the use of different types of memory. A comparison is made between the rates of
counting on a graphics processing unit and a central processor using grids having different resolution capabilities
and various difference schemes of computation of fl ows.
Author:
K. N. Volkov, V. N. Emel′yanov, A. G. Karpenko
Keywords:
graphics processing unit, parallel algorithm, gas dynamics, method of fi nite volumes, unstructured grid
Page:
1031
COMPUTATIONAL AND EXPERIMENTAL INVESTIGATION OF PATTERNS OF COOLANT FLOW IN THE MIXED CORE OF A VVER REACTOR
The paper presents the results of investigations into the hydrodynamics of a three-dimensional coolant fl ow motion
in the mixed core of a VVER (a.k.a. WWER or PWR) reactor. The experiments were conducted on an aerodynamic
research facility test bench with scaled models of core fragments. An investigation has been made into the patterns
of the coolant fl ow motion by experimental fi nding of the velocity vector. Measurement of the fl ow pressure fi eld was
conducted with a fi ve-channel pneumometric (pressure-tube) probe and was then recalculated and converted into the
direction and value of the velocity. To obtain a detailed pattern of a three-dimensional coolant fl ow motion, the most
representative region of the models′ cross section including the space between the fuel (fuel rod bundles) and four
rows of fuel elements of each of the adjacent fuel assemblies was identifi ed and investigated. The general pattern of
the coolant fl ow is represented by plots of transverse velocity distribution as a function of a relative coordinate and
by cartograms of axial velocity distribution. An analysis of the spatial distribution of the fl ow velocity projections in
characteristic regions of the model made it possible to identify the patterns of the coolant fl ow around hydraulically
nonidentical intensifi er grids
Author:
S. M. Dmitriev, A. A. Dobrov, D. V. Doronkov, D. S. Doronkova, M. A. Legchanov, A. N. Pronin, E. V. Rubtsova, A. V. Ryazanov, A. E. Khrobostov, Yu. K. Shvetsov, D. L. Shipov
Keywords:
reactor core, fuel assembly, separation (spacer) grids, intensifi er grids, fl ow defl ectors, coolant hydrodynamics
Page:
1042
THERMOPHYSICAL CHARACTERISTICS OF FIBROUS THERMOPROTECTIVE MATERIALS AT HIGH TEMPERATURES
The present work is devoted to verifi cation of the procedure of determining the thermophysical characteristics of
highly porous fi brous thermoprotective materials under conditions resembling real ones. For creating conditions
close to operational ones, temperature regimes of heating from 300 to 1200 K in vacuum at a pressure within the
range 7.0·10–5–9.0·10–5 bar were realized in the process of experiment. The thermophysical characteristics were
calculated using the data of temperature measurements at the internal points of thermoprotective material samples.
A comparative analysis of the results obtained with the use of different quantities of thermocouples mounted in the
samples is given. The computational algorithm for processing experimental data is based on the solution of the
inverse heat transfer problem by the method of iteration regularization.
Author:
O. M. Alifanov, S. A. Budnik, A. V. Nenarokomov, A. V. Netelev, A. S. Okhapkin
Keywords:
highly porous fi brous thermoprotective materials, method of iteration regularization, thermovacuum test rig
Page:
1052
THERMO-STRESSED STATE OF A HOLLOW POLYMER DIELECTRIC CYLINDER
The paper presents a mathematical model describing the distribution of stresses in a hollow cylinder caused by a
one-dimensional steady temperature fi eld occurring at an assigned fi xed difference of electrical potentials on the
surfaces of a cylinder made of polymer dielectric. A quantitative analysis of the model makes it possible to identify
the effects of temperature dependences of the specifi c electrical resistivity, thermal conductivity coeffi cient, and
mechanical characteristics of the dielectric material on the thermo-stressed state of the cylinder. The model refl ects
the conditions of work of the dielectric layer of a single fi ber high DC-voltage cable. Estimates are given of the
conditions for the occurrence of a thermal breakdown of a dielectric cylindrical layer and of the cylinder′s boundary
state of stress which occurs in the case of planned or emergency nullifi cation of electric potential difference. The
results of such analysis can be useful for identifying possible areas of application of polymer dielectrics in various
electrical devices.
Author:
V. S. Zarubin, V. N. Zimin, A. N. Kuvyrkin, I. Yu. Savel′eva
Keywords:
nonlinear mathematical model, polymer dielectric, one-dimensional temperature distribution, integral relations
Page:
1063
TEMPERATURE FIELD OF A METHANE HYDRATE IN THE PROCESS OF ITS DECOMPOSITION AT A CLOSED-ROOM TEMPERATURE
The temperature fi eld of a methane hydrate in the process of its decomposition at a closed-room temperature was
investigated with the use of a special-purpose experimental setup. The results obtained are expected to be useful for
the storage and transportation of gas hydrates.
Author:
W. S. Chen, C. H. Liu, H. L. Wang, F. C. Hou, Q. Wu
Keywords:
methane hydrate, dissociation, temperature fi eld
Page:
1072
EXPERIMENTAL INVESTIGATION OF A NONSTANDARD LAYOUT OF A MULTIROW HORIZONTAL FINNED-TUBE BUNDLE WITH AN EXHAUST SHAFT
In view of the fact that heat exchangers made of bimetallic fi nned tubes have found wide application in contemporary
technology for the regime of natural convection, it became necessary to take into account the radiative component
that may be appreciable in the total heat fl ux and that depends on the geometric parameters of the bundle and
characteristics of the surface studied. It is suggested in the article to raise the heat power of a multirow fi nned bundle
by applying a nonstandard layout of tubes by placing their upper row above the exhaust shaft, with the remaining
ones under the shaft. From the results of experimental investigations and of a comparative analysis of heat transfer
by radiation and convection of a multirow fi nned-tube heat transfer bundle with an exhaust shaft and different
layouts of tubes, it is shown that the nonstandard layout of fi nned tubes of a multirow heat exchanging bundle makes
it possible to increase the radiant heat fl ux by 1.4–1.5 times. In this case, the total heat transfer rate of the bundle
with the use of a nonstandard layout is increased approximately by 5%. It is shown that it is worthwhile to optimize
the layout of the bundle when the fraction of the radiant fl ux in the total heat fl ow exceeds 10%.
Author:
A. B. Sukhotskii, E. S. Danil′chik, and G. S. Marshalova
Keywords:
fi nned tube, exhaust shaft, zone method of calculation of a radiant heat fl ux, natural convection of air
Page:
1079
DESIGN OF A NEW METHOD FOR OBTAINING THERMAL INSULATION BLOCKS FROM HYDROSILICATE
Design of thermal insulation from porous materials based on hydrosilicates is a promising area of researches. In this paper, the formation of pores is analyzed and the advent of new highly porous heat-insulating materials on the basis of hydrosilicates is proposed. The determination of the thermophysical properties of the studied highly porous materials is based on empirical laboratory investigations of the samples obtained. An analytical study of the formation of pores is carried out. The results of the research on the preparation of a new highly porous heatinsulating material on the hydrosilicate basis are presented. The thermal conductivity of this thermal insulation was found to be equal to 0.114–0.119 W/(m·K), and its specifi c heat at 22oС, to 1.33–1.41 kJ/(kg·K ). The obtained results
confi rm that the developed heat-insulating material meets the requirements upon materials of this kind. From the
proposed hydrosilicates, thermal insulation has been created that is used at JSC Motor Sich for special conditions of
the operation, which confi rms the practicality of the present researches.
Author:
A. M. Pavlenko, A. O. Cheilytko, S. V. Ilin
Keywords:
highly porous material, heat-insulating material, hydrosilicates, pore
Page:
1085