Volume 97, №3
THREE-LAYER PROBLEM ON HEAT EXCHANGE IN A MEDIUM WITH COUNTERFLOWS
With the use of the asymptotic method, it is shown that the three-layer problem on the conjugate heat exchange
in an anisotropic medium with counterfl ows of liquid, formulated in the zero approximation, is equivalent to the
analogous problem formulated using the Newton law. It was established that in the case where the counterfl ows of
liquid in such a medium have equal strengths, the summary convective heat transfer in the medium is suppressed,
and the medium takes new properties consisting in the appearance of heat fl ow mixed in nature, whose value is
determined by the relation similar to the Fourier heat conduction law. By this meant that in the case where a
temperature gradient is superimposed on a three-layer system of equivalent counterfl ows of liquid, in it there arises
a heat fl ow having a value proportional to the temperature gradient in the medium and propagating in the direction
opposite to the direction of this gradient. The eff ective coeffi cient of heat conductivity of medium, generated in
it by the counterfl ows of liquid, separated by an immovable layer, is proportional to the square of the velocity of
these fl ows. An immovable layer in a medium, separating the counterfl ows of liquid, increases the generation of
heat in the medium, and the heat fl ow generated exceeds substantially the molecular one even in the case where it
has a low velocity. Such processes provide the mass exchange in living organisms and their heat exchange with the
environment.
Author:
A. I. Filippov
Keywords:
heat exchange, counterfl ows, eff ective heat conductivity, temperature gradient
Page:
535
DETERMINING THE EFFICIENCY RATIO OF A HEAT-EXCHANGE APPARATUS
The author has proposed the general approach to determining the effi ciency ratio of heat-exchange apparatuses
with diff erent schemes of motion of the heat-transfer agents on the basis of taking account of their fi nal equilibrium
temperature. A procedure has been developed to calculate this temperature for a cocurrent-fl ow scheme of motion of
the heat-transfer agents. The proposed approach makes it possible to consistently determine and to correctly compare
the effi ciency ratios of heat-exchange apparatuses in counterfl ow, cocurrent fl ow, and crossfl ow of hot and cold
heat-transfer agents. The author has given results of calculating the effi ciency ratios of heat-exchange apparatuses
used in the production of liquefi ed natural gas. It has been shown that the maximum operating effi ciency of a heatexchange apparatus is attained with evaporation of the cold heat-transfer agent (coolant), which is characteristic of
the processes of liquefaction of gases
Author:
O. M. Sokovnin
Keywords:
heat-exchange apparatus, cocurrent fl ow, counterfl ow, crossfl ow, effi ciency ratio, fi nal equilibrium temperature
Page:
545
INFLUENCE OF BOUNDARY CONDITIONS FOR THE RADIAL COMPONENT OF MAGNETIC INDUCTION ON HEAT EXCHANGE OF LIQUID IN A SPHERICAL LAYER
The article presents the results of numerical simulation of unsteady-state heat exchange of an electrically conducting
liquid in a spherical concentric layer with account for the Joule heat dissipation. The infl uence of boundary conditions for the radial component of magnetic induction on the evaluation of heat exchange, hydrodynamics, magnetic
induction, and the Nusselt number distribution at small values of the magnetic Reynolds number was studied. The
values of the magnetic Reynolds number at which a change in the intensity of heat exchange occurs on the liquid
layer surface are determined
Author:
S. V. Solov′yov
Keywords:
mathematical simulation, unsteady-state heat exchange, magnetic hydrodynamics, Joule heat dissipation, spherical layer
Page:
552
COOLING OF ELECTRONIC COMPONENTS BY AN ALUMINUM LOOP THERMOSYPHON CONTAINING TWO EVAPORATORS AND ONE CONDENSER
The article presents the results of studies of the parameters of a new fl at aluminum thermosyphon, the evaporator of
which contains two identical parallely operating panels, each of which has 8 minichannels. The panels are united by
single vapor and liquid collectors. The working fl uid is acetone. A study was carried out to investigate the infl uence
of a thermal load and the degree of thermosyphon fi lling with working fl uid on the heat exchange coeffi cients of the
evaporator and condenser, as well as on the thermal resistance of the thermosyphon
Author:
A. A. Artyukh, D. I. Sadchenko, L. L. Vasiliev
Keywords:
thermosyphon, heat exchange, evaporator, condenser, cooling, minichannels, thermal resistance
Page:
566
PRELIMINARY ASSESSMENT OF THE EFFECTIVENESS OF USING A STEAM TURBINE GENERATOR PLANT AS PART OF A SYSTEM ENSURING A THERMAL REGIME BY USING LOOP HEAT PIPES
The problem of using a steam generator plant, operating on the Rankine cycle, to utilize some of the thermal energy
as part of the system for ensuring the thermal regime of a spacecraft is considered. The thermal energy released by
the instrumentation equipment is removed to external radiators using loop heat pipes, after which it is radiated into
outer space. Part of the heat is converted into electricity to maintain the functioning of on-board radio-electronic
equipment. The work assessed the infl uence of a steam generator plant on thermal systems (with a preliminary
solution of a system of thermohydraulic equations with characteristic initial-boundary conditions of loop heat
pipes), its design parameters, such as the area of external radiators and the mass of the system, and conclusions
are made about the feasibility of its use. This system for ensuring thermal conditions using loop heat pipes can be
useful for energy-consuming unmanned spacecraft with low restrictions on the mass and size characteristics of the
device.
Author:
N. O. Borshchev
Keywords:
thermal control system, steam generator plant, Carnot cycle, area of the external radiator-emitter, Rankine cycle
Page:
575
THE PROSPECT OF USING MEMBRANE DEVICES FOR COLD PRODUCTION AS AN ALTERNATIVE TO THE ABSORPTION REFRIGERATING INSTALLATION
The papers considers the problems relating to the use of separation processes in membrane apparatuses for the
production of cold in mix refrigerating machines as an alternative to absorption refrigerating machines, which will
ensure a more stable process for obtaining a refrigerant from the mixture, reduce material costs for the production of
a refrigerating installation, and increase the energy effi ciency of the refrigerating installation operating on mixture
components. An analysis of the use of traditional absorption and membrane refrigerating machines was carried out
from the point of view of energy effi ciency and the number of working elements. The primary method for calculating
the process of separation of an absorbent–refrigerant mixture based on reverse osmosis processes is presented
Author:
M. V. Shamarov
Keywords:
refrigerating installation, absorption, separating membrane, selectivity, separation area, absorbent, refrigerant
Page:
585
SCHWARZ PRIMITIVE SURFACE-BASED HEAT EXCHANGERS ADAPTED FOR ADDITIVE MANUFACTURE
The introduction of additive technologies may require an update in the methods of developing heat exchangers (HE).
A variant of the methodology of HE parametric design has been demonstrated on a Schwarz P-surface. A 3D-calculaiton of a row-by-row representative HE model has been used to obtain data for deriving empirical criterial dependences suited for a fast engineering calculation of HE thermohydraulic characteristics. Within the framework of the
technological testing and approval of HE manufacture on Schwarz P-surfaces, possibilities have been demonstrated
for their scaling and for a reduction in roughness in the course of postprocessing for diff erent materials
Author:
A. L. Svetlakov, I. A. Gulimovskii, I. S. Verbanov, D. V. Maslova
Keywords:
heat exchanger, Schwarz P-surface, thermohydraulic criterial dependences, additive manufacture, technological testing
Page:
593
COEFFICIENT OF HEAT TRANSFER OF A CYLINDRICAL PIPE WITH A CONSTANT TEMPERATURE AT LARGE TIMES
The author has given a solution to the problem on the distribution of heat around a cylindrical rod of infi nitely small
radius and with a constant temperature. The obtained solution belongs to a novel class of self-similar problems
with an arbitrary positive parameter approaching zero as close as is wished. Based on the obtained results, an
asymptotic (at large times) expression has been found for the coeffi cient of heat transfer of a cylindrical pipe with a
heat-insulation shell
Author:
K. O. Sabdenov
Keywords:
heat-transfer coeffi cient, heat loss, pipe with heat insulation, self-similar problem
Page:
604
BROWNIAN DIFFUSION OF NANOPARTICLES IN A LIQUID AND A "LASER MILL"
A description is given of the operating principle of the so-called "laser mill" making it possible to obtain assemblies
of virtually monodisperse spherical metal nanoparticles from a colloidal solution of nanoparticles of various size.
A laser mill occurs as a result of exposure of such a solution to a powerful pulse-periodic laser radiation, with the
characteristic dimension of the forming monodisperse nanoparticles being much smaller than the laser radiation
wavelength
Author:
S. P. Fisenko
Keywords:
absorption coeffi cient, heat of evaporation, radiation wavelength, laser bean energy
Page:
613
NANOGRANULAR NATURE OF CSH: EXPERIMENTAL CONFIRMATION BY NANOINDENTATION
Hydration of cement materials is accompanied by the formation of calcium silicate hydrates (CSH). Accordingly,
the hydration process is completed in the early, middle, and late periods, leading to the formation of two types of
CSH phases: of low density (LD) and high density (HD). Usually, under normal conditions, LD CSH is formed in
the middle period, while the formation of HD CSH predominates in the later stage. In using the nanoindentation
method, it becomes possible to explain the nanogranular nature of the CSH gel, which is characterized by the
contact forces of the CSH gel particles for these phases. Studies of cement stone samples at W/C = 0.21 and at
the content of hydrothermal SiO2 nanoparticles in the combined additive 0.000006 wt.% and multilayer carbon
nanotubes (MCNT) 0.00004 wt.% for cement showed that the eff ect of nanoparticles on the structure of the CSH
gel becomes more pronounced, since the volume fraction of the LD phase of the CSH gel with a low packing density
of nanogranules becomes signifi cantly lower than the fraction of the HD phase with increased hexagonal packing
density of nanogranules.
Author:
E. N. Polonina, S. N. Leonovich, S. A. Zhdanok
Keywords:
nanoparticles, nanoindentation, nanogranules, packing density
Page:
617
MATHEMATICAL MODELING OF SiO2 NANOPARTICLE CONDENSATION UNDER LOW-TEMPERATURE PLASMA CONDITIONS
A model has been proposed that describes the processes of nucleation and growth of SiO2 nanoparticles from the
gas phase formed in a plasma-chemical arc-discharge reactor. The value of the median diameter at a temperature
T > 1500 K is determined by the rate of nucleation, deposition of molecules onto the particles formed, and by the
rate of coagulation of formed particles. The main processes determining the change in the median diameter at
temperatures 1000 < T < 1500 K are precipitation and coagulation. At a low temperature, T < 1000 K, a change in
the median diameter occurs due to the deposition of molecules from the gas phase on the formed particles
Author:
O. V. Matvienko, V. V. Shekhovtsov
Keywords:
silicon dioxide nanopowder, nucleation, condensation, coagulation, numerical simulation
Page:
625
MATHEMATICAL MODELING OF SiO2 NANOPARTICLE CONDENSATION UNDER LOW-TEMPERATURE PLASMA CONDITIONS
A model has been proposed that describes the processes of nucleation and growth of SiO2 nanoparticles from the
gas phase formed in a plasma-chemical arc-discharge reactor. The value of the median diameter at a temperature
T > 1500 K is determined by the rate of nucleation, deposition of molecules onto the particles formed, and by the
rate of coagulation of formed particles. The main processes determining the change in the median diameter at
temperatures 1000 < T < 1500 K are precipitation and coagulation. At a low temperature, T < 1000 K, a change in
the median diameter occurs due to the deposition of molecules from the gas phase on the formed particles
Author:
O. V. Matvienko, V. V. Shekhovtsov
Keywords:
silicon dioxide nanopowder, nucleation, condensation, coagulation, numerical simulation
Page:
625
THERMAL CONDUCTIVITY OF MIXED REFRIGERANTS R-125/R-134A AND R-32/R-125
The results of measurements of the thermal conductivity carried out in a gas phase for six binary mixed refrigerants,
consisting of hydrofl uorocarbons R-125, R-134a, and R32, are analyzed. For each mixture, an equation is given for
calculating its thermal conductivity depending on temperature and pressure. The previously proposed model for
predicting the thermal conductivity of vapors of mixed refrigerants in a wide range of state parameters has been
refi ned in application to the R-125/R-134a and R32/R-125 systems
Author:
E. P. Raschektaeva, S. V. Stankus
Keywords:
thermal conductivity of vapors, experimental data, refrigerant mixtures, forecasting
Page:
636
TOWARD QUANTITATIVE INTERPRETATION OF THERMOGRAMS OVER THE WELLBORE ON OIL DEGASSING WITH REGARD TO THERMOHYDRODYNAMIC HEAT SOURCES
Based on numerical modeling of thermohydrodynamic processes in the wellbore under conditions of oil degassing,
the possibility of estimating the coeffi cient of gas solubility in oil and the well fl ow rate is investigated based on an
analysis of temperature distribution along the wellbore. It is shown that degassing of oil in the wellbore or in a bed
leads to the formation of temperature cooling anomalies, which can be used to solve certain oilfi eld problems. The
results obtained can be used in planning fi eld-geophysical studies and interpreting the results of temperature studies
of wells during the production of live crude
Author:
I. V. Kanafi n, R. F. Sharafutdinov, R. A. Valiullin, F. F. Davletshin
Keywords:
thermometry, two-phase fl ow, oil degassing, heat of oil degassing, well
Page:
641
MODELING THE PROCESSES OF EXTRACTION OF RETROGRADE CONDENSATE FROM DEPLETED GAS CONDENSATE RESERVOIRS USING HORIZONTAL WELLS
Based on mathematical modeling, an investigation has been made into the processes of segregational separation of
hydrocarbon phases in the regime of depletion and extraction of retrograde condensate from depleted gas condensate
reservoirs. It has been established that the occurrence of segregation processes in the case of depletion of gas
condensate reservoirs results in the formation of a man-made condensate bank near the gas–water contact. An
effi cient method of extraction of retrograde condensate from man-made condensate banks is waterfl ooding
Author:
M. S. Khalilov
Keywords:
depletion regime, retrograde condensate, phase state of gas condensate mixtures, mathematical modeling, isothermal fl ow
Page:
649
DYNAMICS OF HYDRODYNAMIC PRESSURE IN THE WELL WITH PACKER SUCKER-ROD WELL PUMPS
A study is made of the possibility of using sucker-rod well pumps for oil withdrawal from the below-packer space
of a producing well as a method of continuous excitation of fl uctuations of hydrodynamic pressure in the wellbore
for wave action on the face zone of this well. The action of pulses of hydrodynamic pressure on the pay formation
in the nearwellbore zone contributes to the cleaning of microparticles clogging the rock′s void space from it, to the
development of a crack system in the rock, to the reduction in the effi cient viscosity of formation fl uids possessing
viscoplastic properties, etc. This action tends to raise the effi ciency of producing wells.
By mathematical-modeling methods, the author has obtained an analytical expression describing, with a high
degree of accuracy, the dynamics of hydrodynamic pressure in the wellbore over one period of operation of suckerrod well pumps. It has been shown that in high-permeability formations with a formation-fl uid viscosity close to the
viscosity of water, the amplitude of hydrodynamic-pressure fl uctuations in the below-packer zone of the wellbore
is relatively small and is measured by values of the order of hundredth fractions of an MPa. On reduction in the
permeability of reservoir rock, rise in the viscosity of the formation fl uid, and growth in the well yield, the amplitude
of pressure fl uctuations grows up to ~1 MPa or more, which is responsible for the high effi ciency of wave action on
face zones. The obtained results may be used to assess the effi ciency of use of sucker-rod well pumps in combination
with packers to stimulate fi ltration processes in the face zones of oil-producing wells.
Author:
A. V. Svalov
Keywords:
producing well, sucker-rod well pump, packer, wave action, well effi ciency
Page:
657
RHEOLOGICAL FEATURES OF WATER FLOW IN MICROCRACKS
Rheophysical phenomena during the fl ow of a viscous fl uid (water) in diff erently opened fl at microcracks have
been studied. The role of the electrokinetic factor in the manifestation of the nonlinear rheological eff ect in a water
fl ow in a microchannel model — the transformation of a Newtonian fl uid into a non-Newtonian one — is examined
experimentally. Water fl ow curves were recorded and, based on the Bingham model, its rheological parameters
were assessed for diff erently opened microcracks. It has been established that the non-Newtonian nature of water in
microcracks is determined mainly by the value of the electrokinetic potential of the fl ow, and by reducing it, using
antistatic additives, the nonlinear nature of the fl ow can be weakened signifi cantly.
Author:
F. G. Veliev, M. A. Mamedova, A. R. Aslanova
Keywords:
microcrak, microcrack opening, fl ow curves, double electric layer, streaming potential, antistatic additives, ultimate shear stress, structural viscosity
Page:
663
FORCE EFFECT OF A VORTEX RING ON A FLAT OBSTACLE
Numerical modeling of the interaction of a vortex ring with a normally located fl at obstacle was performed based
on the nonstationary Navier–Stokes equations, for discretization of which the fi nite volume method was used. A
qualitative picture of the change in the structure of a vortex ring during its interaction with the obstacle is presented.
The distributions of pressure in time on the obstacle and the change in the longitudinal force acting on the obstacle
are determined
Author:
K. N. Volkov, V. N. Emel′yanov, I. E. Kapranov
Keywords:
computational gas dynamics, vortex dynamics, vortex ring, vorticity, obstacle
Page:
668
ADVECTIVE THERMOACOUSTIC FLOW IN A ROTATING HORIZONTAL LIQUID LAYER
Exact analytical solution of the Navier–Stokes equations, that describes, in the Boussinesq approximation, the fl ow
of an incompressible liquid in the horizontal, plane layer with solid boundaries, rotating about a vertical axis, is
presented. The fl ow of the liquid in this layer is advective and thermoacoustic in nature, and it is due to the constant
longitudinal temperature gradient at the boundaries of the layer and to the acoustic wave propagating in it. The
length of this wave is assumed to be comparable with the thickness of the layer, and the period of acoustic vibrations
of the liquid in it is small compared to the characteristic convection times. Because of this, it is advantageous to
defi ne the averaged liquid fl ow in the layer. The properties of the solution obtained are investigated and the infl uence
of the Taylor number of the liquid fl ow on its velocity and temperature profi les at constant Grashof, Reynolds, and
Prandtl numbers is determined.
Author:
K. G. Shvartz
Keywords:
: horizontal convection, advective fl ows, exact solution, acoustic wave, rotation
Page:
675
NUMERICAL VERIFICATION OF THE SOLUTION TO THE PROBLEM OF EMPTY CAVITY COLLAPSE IN A VISCOUS FLUID
Details of calculation of the critical Reynolds number that separates two diff erent types of agglomeration of bubbles
in a viscous fl uid are given
Author:
N. S. Khabeev, M. F. Teimurov
Keywords:
bubble, collapse, viscous fl uid
Page:
683
ELECTROVORTEX FLOW BETWEEN TWO CYLINDERS IN LINEAR APPROXIMATION
A problem has been solved on electrovortex fl ow between two cylinders in a self-similar formulation within the
framework of Stokes approximation implying a rather low velocity of the fl ow and its fast entry into a stationary
mode, which makes it possible to signifi cantly simplify the solution of the Navier–Stokes equation and to establish the
relation between diff erent fl ow parameters. Results of an analytical solution of the problem supported by numerical
assessments are presented.
Author:
E. A. Mikhailov, A. P. Stepanova, A. A. Taranyuk, A. Yu. Chudnovskii
Keywords:
electrovortex fl ow, liquid metal, self-similarity, Navier–Stokes equation
Page:
687
USE OF SHAPED CHARGES WITH VARIOUS LINERS FOR THE FORMATION OF HIGH-VELOCITY ALUMINUM PARTICLES
Tests of rocket and space equipment objects in terrestrial conditions for shock resistance to the impact of meteoroids
and space debris can be carried out using shaped charges. To substantiate the design parameters of shaped charges
ensuring the formation of aluminum particles in a broad velocity range (from 2.5 to 16 km/s), numerical simulation
has been conducted for the process of the said formation within the framework of a two-dimensional axisymmetric
problem of continuum mechanics using ANSYS/AUTODYN, ERUDIT, and KOLDUN computer systems. In
calculations, consideration has been given to shaped charges with a diameter from 20 to 100 mm with aluminum
liners of various shape. It has been shown that the formation of particles with velocities close to the lower boundary
of the considered range is ensured by gently sloping segmental degressive-thickness liners. For the formation of
higher-velocity particles with velocities above 5 km/s, it is suggested that use be made of combined liners whose
jet-forming portion has the shape of a hemisphere of constant thickness or the shape of a semi-ellipsoid or semisuperellipsoid of rotation
Author:
V. I. Kolpakov, S. V. Fedorov, E. P. Vinogradova, I. A. Bolotina
Keywords:
space debris, meteoroid impact, high-velocity aluminum element, explosion, shaped charge, segmental liner, combined liner, numerical simulation
Page:
695
DYNAMICS OF PENETRATION INTO CONCRETE BY DUMMY STRIKERS IN THE ABSENCE OR PRESENCE OF A DETACHABLE SABOT
Based on numerical simulation within the framework of a two-dimensional axisymmetric problem of continuum
mechanics, an analysis has been made of penetration into a semi-infi nite barrier by dummy strikers with diameters
of 14 and 18 mm and an initial velocity of 1200 m/s with and without account for the eff ects of the detachable sabot
used for accelerating the dummies in the barrel of a ballistic installation. In simulating the penetration by dummy
strikers in a sabot, a reduction was registered in the depth of penetration by a little over 10% with increase in the
maximum overload compared to the case of penetration in the absence of a sabot. A cause has been identifi ed for
the sabot′s negative eff ects on dummy strikers′ penetration, lying in an increase of tangential stresses acting on the
surface of the dummies′ contact with the adjacent layer of loosened concrete due to precompression of this layer by
the sabot until the sabot′s complete detachment from the dummy striker
Author:
S. V. Fedorov, V. A. Veldanov, A. L. Isaev, A. Yu. Perfi l′ev, N. A. Fedorov
Keywords:
concrete barrier, dummy striker, detachable sabot, high-velocity penetration, depth of penetration, overload, numerical simulation
Page:
705
APPLICATION OF THE SEDIMENTATION SIMILARITY PARAMETER WHEN GENERALIZING EXPERIMENTAL RESULTS UNDER CONDITIONS OF NATURAL CONVECTION
The application of a new sedimentation similarity parameter, containing an electrochemical number, is considered.
Generalization of the results of experimental studies in various media under conditions of natural convection was
carried out. New dimensionless equations of heat exchange have been derived. A new method has been developed for
calculating the emission of heat during local formation of deposits on the heat exchange surface
Author:
K. V. Altunin
Keywords:
natural convection, similarity parameter, sedimentation, kerosene, water, air
Page:
715
NUMERICAL STUDY ON A CONDUCTING WAVY FIN IN A RECTANGULAR CAVITY
The transition of the steady fl uid fl ow in a diff erently heated cavity with an adiabatic wavy fi n installed on its hot
wall to the unsteady one under the action of this fi n was simulated numerically depending on the geometry of the fi n.
It was established that the thermal behavior of the fl uid in the cavity is greatly dependent on the relative undulation
of the fi n, and the heat transfer in the cavity increases with increase in the fi n-developed heat exchange surface of
the cavity
Author:
M. S. Bouchouicha, O. Ladjedel, K. Boualem, F. Zemani, T. Yahiaouid
Keywords:
cavity, wavy fi n, ripple, natural convection, Rayleigh number
Page:
724
INFLUENCES OF VARIABLE VISCOSITY AND VARIABLE THERMAL CONDUCTIVITY ON A MIXED CONVECTIVE HYDROMAGNETIC FLOW IN A VERTICAL CHANNEL WITH THERMOPHORETIC DEPOSITION
The infl uences of variable viscosity and thermal conductivity on a steady, laminar, viscous, incompressible,
hydromagnetic fl ow passing through a channel fi lled with a porous medium are investigated. The eff ects of heat
source, thermal radiation, thermophoretic deposition, and Soret and Dufour numbers are considered. The governing
equations are solved by the MATLAB bvp4c solver. It is found that increases in the viscosity parameter, thermal
conductivity parameter, and the thermophoretic coeffi cient reduce the fl uid velocity, while increasing radiation
parameter and Dufour number enhance it. An increase in the thermal conductivity parameter raises the concentration,
but reduces the temperature. The infl uences of the relevant parameters on the skin friction and Sherwood and Nusselt
numbers are presented in tabular form and analyzed.
Author:
U. J. Das, I. Patgiri
Keywords:
hydromagnetic fl ow, variable viscosity, variable thermal conductivity, thermophoretic deposition, thermal radiation, bvp4c solver
Page:
733
INFLUENCE OF THE LASER PULSE ANNEALING OF THE SILICON IMPLANTED WITH INDIUM AND ARSENIC IONS ON ITS OPTICAL AND STRUCTURAL PROPERTIES
Optical and structural properties of silicon layers implanted with indium and arsenic ions and annealed by laser pulses were investigated. It is shown with the use of the Rutherford backscattering and channeling methods that the fraction of indium and arsenic atoms in the silicon crystal lattice of such a layer comprises 31–35%. It was established by the radiation absorption spectra of the indicated layers that the degree of absorption of the nearinfrared radiation (1.1–2.4 μm) by them is larger by several orders of magnitude than that of these layers in the initial state with no implantation and annealing (the absorption effi ciency comprises 50–60%). The effi ciency of absorption of the mid-infrared radiation quanta (3–25 μm) by a silicon layer implanted with indium and arsenic ions is higher by approximately three times than that of the initial one at a laser radiation energy density of 2.0–2.5 J/cm
2
. A broad band 1.1–1.6 μm has been revealed in the photoluminescence spectra of the silicon layers
implanted with indium and arsenic ions and annealed by laser pulses
Author:
F. F. Komarov, O. V. Mil'chanin, I. N. Parchomenko, P. V. Kuchinskii, A. E. Al'zhanova, M. A. Mokhovikov, E. Wendler
Keywords:
hyperdoped silicon, laser pulse annealing, Rutherford backscattering, radiation absorption spectrum, photoluminescence
Page:
745
OPTIMIZATION OF THE REGIMES OF OBTAINING DIAMOND-LIKE CARBON COATINGS WITH HIGH PERFORMANCE CHARACTERISTICS BY THE LASER-PLASMA METHOD
The formation of a diamond-like carbon coating on a substrate as a result of the action of the radiation of an industrial laser (t ~ 20 ns, λ = 1.06 μm) on a target of the highly oriented pyrolytic UPV-1 graphite in a vacuum was investigated. It is shown that by changing the power density of the laser radiation on the surface of such a target, the velocity of scanning of the laser beam over the target surface, the laser pulse repetition frequency, and the temperature of the target, one can control the ratio between the sp2
- and sp3
-carbon bonds in the coating applied to a substrate. It was established that a diamond-like carbon coating with a predominant content of the sp3
-bonded carbon is formed at a laser power density q ≥ 5.6∙108
W/cm
2
. In this case, it is advisable to select the laser pulse repetition frequency and the velocity of scanning of a laser beam over the surface of a target so that 10 to 14 laser pulses fall successively into one and the same area of the target surface. It is shown that, in the case where a target has a temperature T ≥ 423 K, the content of the sp3
-linked carbon in the coating applied to a substrate decreases
sharply, with the result that the properties of the coating deteriorate.
Author:
V. K. Goncharov, G. A. Gusakov, M. V. Puzyrev
Keywords:
erosion laser torch, ion fl ows, diamond-like carbon coatings
Page:
753
HYBRID LATTICE BOLTZMANN METHOD FOR 3D NATURAL CONVECTION COMBINED WITH VOLUMETRIC RADIATION
A hybrid lattice Boltzmann model was developed to examine the eff ect of volumetric thermal radiation on threedimensional natural convection. Within this model, a fl uid fl ow was computed by the lattice Boltzmann method in terms of the D3Q19 scheme and Bhatnagar–Gross–Krook approximation. On the other hand, a fi nite-diff erence technique was applied to solve the energy equation. To determine the radiative heat fl ux, the Rosseland approximation was used. The eff ect of the Rayleigh number Ra and the radiation parameter Rd on the temperature, fl ow behavior, and the mean Nusselt number was studied in the ranges 104 ≤ Ra ≤ 106
and 0 < Rd ≤ 5. It was found that thermal
radiation weakened natural convective mechanism of heat transfer. The mean convective Nusselt number increased
with the Rayleigh number and decreased with increase in the radiation parameter
Author:
A. Neea, A. K. Hussein
Keywords:
Rosseland radiation, BGK approximation, D3Q19 scheme, fi nite-diff erence method
Page:
766
APPROXIMATE ANALYTICAL SOLUTION OF THE BRATU BOUNDARY-VALUE PROBLEM
Three new approaches to the solution of the Bratu problem are presented. The fi rst approach realizes the idea of
successive diff erentiating the initial equation of this problem with expansion of the sought for function at the symmetry point of a space. The second approach is associated with the additional integration of the diff erential Bratu
equation, and it represents a hybrid integral method. The third approach is based on the combined application of the
successive diff erentiation of the Bratu equation, the hybrid integral method, the expansion of the sought for function
at two points of the space, and an additional integral relation. The indicated approaches are characterized by the
simplicity of the calculations required for their realization, and they reduce the solution of the Bratu problem to the
solution of a system of linear algebraic equations. The numerical results of solving this problem demonstrate the
high effi ciency of the approaches proposed, providing the obtaining of the solutions whose accuracy exceeds the
accuracy of the analogous solutions, obtained on the basis of the known numerical and numerical-analytical methods, by three to fi ve orders of magnitude. This is especially true for the third approach that allows one to obtain two
classical solutions of the Bratu problem fairly simply and with a very high accuracy. It is shown that the obtaining
of an approximate solution of the Bratu problem with this approach calls for a small number of series terms, and the
solutions obtained converge quickly and approximate the problem highly exactly
Author:
V. A. Kot
Keywords:
boundary-value Bratu problem, hybrid integral method, generalized integral method
Page:
774
FREE-CONVECTION HEAT TRANSFER ON MULTIROW BUNDLES OF FINNED TUBES WITH CIRCULAR FINS
The use of free convection in various industries grows, which is due to the increase in heat loads, and also to the
closer attention to energy effi ciency. Thus, for air-cooled apparatuses at certain parameters of the outside air,
there is a possibility to decouple fan drives and to operate the apparatuses in an energy-saving free-convection
regime. Here, a distinctive feature of the free-convection regime are high values of heat-transfer coeffi cients to
compensate for which the heat-transfer surface on the source side of the air is increased by fi nning the tubes. With
the aim of raising the effi ciency of heat-transfer processes, it is expedient to optimize the geometric parameters and
arrangement of a bundle, the number of rows, and the location of the bundle in space.
The paper presents a review of experimental and numerical investigations into the heat transfer of multirow
horizontal and inclined bundles of fi nned tubes in a free-convection regime. This paper is a continuation of [1] in
which a review has been presented of experimental and numerical investigations into the free-convection heat transfer
on air-cooled annular-fi nned tubes and single-row bundles thereof. Importantly, the character of the dependences
of the heat transfer of single-row bundles on the transverse pitch of the tubes diff ers fundamentally from similar
dependences for multirow staggered bundles because of the infl uence of upper rows
Author:
E. S. Danil′chika, G. S. Marshalova, A. B. Sukhotskii
Keywords:
air-cooled apparatuses, free convection, bimetal fi nned tube, heat-exchange multirow bundle, Nusselt number, Grashof number, Rayleigh number
Page:
801