Volume 98, №5

OPTIMAL HEAT EXCHANGE

An investigation has been made into the limits of the heat exchange process at limitations placed on the heat
load and the heat-transfer coefficient, for a constant heat capacity of flows and for a heat capacity depending
on temperature. In particular, such dependence occurs for flows changing their phase state. It is shown that the
replacement of variables in a mathematical model of a process makes it possible to obtain solutions retaining its form
at any kinetics. The notion of thermodynamically equivalent heat-exchange systems has been introduced, which has
made it possible to reduce the synthesis of a multi-flow heat-exchange system to solving two ordinary differential
equations with separable variables describing a two-flow heat exchange between flows with variable heat capacity
is suggested. Based on the obtained results, an algorithm for synthesis of multi-flow heat-exchange systems is
suggested. In the system being synthesized, each flow can contact several flows, limitations on temperatures, flow
rates and heat capacities of all or part of flows dictated by the technological process integrated with the system
are fulfilled. The system′s synthesis implies the selection of a structure of contacts, values of free parameters of the
flows, a distribution of contact surfaces and heat loads between two-flow heat exchange cells
Author:  A. M. Tsirlin
Keywords:  two- and multi-flow heat exchange, heat exchange kinetics, heat load, energy dissipation, thermal conductivity coefficient, optimal heat exchange system, entropy production
Page:  1187

MARINCA–HERISANU OPTIMAL HOMOTOPY ASYMPTOTIC METHOD AS AN UNSUCCESSFUL MODIFICATION OF THE LIAO HOMOTOPY ANALYSIS METHOD: NONLINEAR HEAT TRANSFER

The Liao optimal method of homotopy analysis was compared with the Marinca–Herisanu optimal homotopy
analysis method by the example of solving two test problems on nonlinear heat transfer. This comparison has shown
that the solutions obtained using the Liao method are either practically identical to the solutions obtained by the
Marinca–Herisanu method or are substantially more exact. Moreover, the obtaining of solutions with the use of the
Marinca–Herisanu method is highly labor-intensive and requires much more time as compared to the Liao method.
Author:  V. A. Kot
Keywords:  nonlinear differential equations, approximate solution, nonlinear heat transfer, optimal method of homotopy analysis, optimal homotopy asymptotic method
Page:  1201

COMBUSTION OF COMPOSITES FROM FRAGMENTED POROUS SILICON AND SODIUM PERCHLORATE MONOHYDRATE IN INERT GASES, NITROGEN, AND AIR

In creating energy-rich composites based on nanostructured silicon, it is topical to ensure stable characteristics
of their combustion. In this connection, establishing conditions and mechanisms for the appearance of precursors,
i.e., sources of ignition ahead of the front of a combustion wave and their influence on the course of the process,
is of importance. In the work, the authors have presented the results of investigation into the combustion of the
composites with combinations of their parameters using high-speed photography and the shadow method of
visualization of disturbances in gas media at different pressures in the substrates with a wall thickness of 50 μm to
3 mm from materials with excellent acoustic impedance. Possible causes of formation of the precursors have been
indicated, in particular, the instability of the burning velocity of the composites and the low humidity of the sodium-
perchlorate monohydrate in them.

Author:  V. N. Mironov, E. S. Demukh, O. G. Penyazkov, K. L. Sevruk, I. I. Chernukho
Keywords:  nanosilicon, sodium perchlorate, energy-saturated composites, precursors, stability of combustion
Page:  1223

MATHEMATICAL MODELING OF HEAT AND MASS TRANSFER PROCESSES IN IMPLEMENTING THE TECHNOLOGY OF in situ COMBUSTION

A simplified approach to modeling in situ combustion is suggested. For its implementation, a one-dimensional
physical and mathematical model has been developed on the basis of the laws of conservation of the mass of phases
(oxidizer, oil, water, and combustion gases), Darcy′s laws, and the closing relation for saturations of a formation
with phases. Distributions of saturations of the formation with phases and of the pressure in the formation have
been obtained. Based on numerical experiments, it is shown that the main part of oxygen burns up in the bottomhole
zone, and the distribution of pressure in the formation is close to linear.
Author:  A. Ya. Gilmanov, D. É. Plisova, A. P. Shevelev
Keywords:  in situ combustion, heat and mass transfer, exothermic reactions, mechanics of multiphase systems, oil recovery, mathematical modeling, saturation, phases
Page:  1234

COMPARATIVE ANALYSIS OF COMBUSTION PERFORMANCE USING PURE AND BLENDED HYDROCARBON FUELS IN A PULSE DETONATION ENGINE

A pulse detonation engine (PDE) is a supersonic propulsive device used in aerospace vehicles. PDE employs
periodic detonations to provide power or propulsion. In the present work, the Zeldovich–von Neumann–Doring
(ZND) model is used to assess PDE performance for pure hydrocarbon and hydrocarbon-blended fuels. The
combustion flame temperature ratio, detonation velocity, pressure ratio, and performance parameters like specific
thrust and specific impulse are analytically calculated for various fuels. The novelty of the present research is
the fact that thermophysical and performance characteristics of hydrocarbon fuels and of their blends have
approximately the same results as given in the NASA Chemical Equilibrium with Applications (NASA CEA) data.
All of the parameters' values fall within the acceptable range of the NASA CEA described values. The hydrocarbon
fuels such as propane, butane, kerosene, and methane are safe, clean-burning, nontoxic, great energy sources, and
are used as alternative hydrocarbon fuels in PDE.
Author:  Mahammadsalman Warimani, M. H. Azami, N. Alam, S. A. Khan, Suhas Patil, M. K. Ramis
Keywords:  analytical approach, hydrocarbon-blended fuel, pulse detonation engine, specific impulse, ZND model
Page:  1240

THERMODYNAMIC SUBSTANTIATION OF THE EXPEDIENCY OF REGENERATION OF FLUORINE AND LITHIUM FROM LITHIUM- AND FLUORINE-CONTAINING SALTS. LITHIUM TETRAFLUOROBORATE

Using thermochemical calculations and calculations of thermodynamically equilibrium compositions of substances
in the groups of elements Li–B–F–O–H and Li–B–F–O–H–C, the authors have shown the expediency of regenera-
tion of fluorine and lithium from lithium tetrafluoroborate (component of the electrolyte of lithium-ion batteries) in
its interaction with hydrogen or methane and oxygen in a combustion regime for closing the cycle "production–op-
eration–utilization of lithium-ion batteries" for fluorine and lithium.
Author:  M. A. Olisov, D. S. Pashkevich, A. A. Pletnev, V. V. Kapustin
Keywords:  lithium tetrafluoroborate, lithium fluoride, boron trifluoride, hydrogen fluoride, thermodynamic equilibrium, combustion
Page:  1252

THERMODYNAMIC JUSTIFICATION OF THE FEASIBILITY OF REGENERATION OF FLUORINE AND LITHIUM FROM LITHIUM- AND FLUORINE-CONTAINING SALTS. LITHIUM HEXAFLUOROPHOSPHATE

Using thermochemical calculations and calculations of thermodynamic equilibrium compositions of substances
in the Li–P–F–O–H and Li–P–F–O–H–C element groups, the feasibility of regenerating fluorine and lithium from
lithium hexafluorophosphate (a component of the electrolyte of lithium-ion batteries) during its interaction with
hydrogen or with methane and oxygen in combustion mode to close the production–operation–utilization cycle of
lithium-ion batteries for fluorine and lithium has been demonstrated
Author:  M. A. Olisov, D. S. Pashkevich, A. A. Pletnev, V. V. Kapustin
Keywords:  lithium hexafluorophosphate, lithium fluoride, hydrogen fluoride, thermodynamic equilibrium, combustion
Page:  1262

CONVECTIVE HEAT TRANSFER OF A SINGLE DROP-SHAPED TUBE

The paper presents the results of investigating hydraulic losses and convective heat transfer of single drop-shaped
tubes in air flow around them on both the side of the small diameter and the side of the large diameter in the range
of Reynolds numbers 1.5∙10 ⁴ –7∙10 ⁴ . A similarity equation Nu = f (Re) is suggested, allowing an estimate of a total
heat transfer of drop-shaped tubes with an error of ±2.5%, and similarity equations Eu = f (Re) are proposed, mak-
ing it possible to assess the hydraulic losses in flow around them on the side of the large diameter (with an error
of ±(2–20)% and the small diameter (with an error of ±2%), respectively. It is shown that the use of drop-shaped
tubes as elements of heat exchange devices is promising. The obtained results can serve as the basis for further
investigations of hydraulic losses and heat transfer of drop-shaped tubes.
Author:  Yu. V. Zhukova, T. A. Baranova, A. D. Chorny, I. A. Popov
Keywords:  computational hydrogasdynamics, turbulence, convective heat transfer, hydraulic losses, similarity equation
Page:  1267

CONTROL OF SUBSONIC FLOW AROUND A SEMICIRCULAR AIRFOIL WITH THE USE OF SLOT SUCTION IN VORTEX CELLS

With the use of multiblock computational technologies and the shear stress transport model modified with regard
for the curvature of streamlines, calculations of the nonstationary turbulent flow of an incompressible fluid around
a semicircular airflow, on the contour of which one or two circular vortex cells with slot suction are placed, at a
zero angle of attack have been performed. On the basis of the calculation data obtained, regimes of stabilizing the
flow around such an airfoil, close to the flow without separation, and the possibility of achievement of the extremal
lift coefficient C _y = 5.8 by it at a lift-drag ratio K = 10, determined with account of the energy expended for the
suction in the vortex cells, have been revealed. It was established that when the Mach number of the undisturbed
flow around a semicircular airflow with two vortex cells increases to the critical value, C _y and K of the airfoil
increase. In this case, C _ymax and K _max are of the order of 6.2 and 14.5, respectively. In the case of flow around this
airfoil at a Mach number larger than M _cr, the second vortex cell does not function, and the flow around the airfoil
becomes detached
Author:  S. A. Isaev, D.V. Nikushchenko, A. G. Sudakov, L. P. Yunakov, N. V. Tryaskin
Keywords:  semicircular airfoil, vortex cell, slot suction, turbulence, calculation
Page:  1278

EXTREMAL INTENSIFICATION OF TURBULENT HEAT EXCHANGE IN A CHANNEL WITH AN INCLINED TRENCH OF OPTIMAL LENGTH

The extremal intensification of turbulent heat exchange in a narrow plane-parallel channel with an inclined trench
of optimal length, placed on its heated wall, as a result of the formation of a tornado-like vortex structure and
a transverse lumped pressure drop in the leading part of the trench was investigated. Correlation between the
increase in the indicated drop to a large value and the increases in the length of the trench to 0.1 in the case where
the trench shape is close to the shape of a spherical dimple and to 0.34 in the case of a long trench with a depth of
0.39, inclined to the channel wall at an angle of 45 ^o , has been established. It is shown that, as the length of a trench
in the channel increases, a detached turbulent flow in it is intensified, and the maximum velocities of the reverse
flow and of the secondary swirling flow reach 0.43 and 0.83, respectively, compared to 0.27 for a spherical dimple.
The minimum relative friction and the maximum relative heat transfer in the central cross section of the trench at
its inlet are stabilized at a level of –1.6 and 1.6 in the case where the trench has a length larger than 4. A maximum
relative heat transfer from the channel region of variable area with a long inclined trench, having spherical ends,
is attained in the case where the trench has a length of 3, and this maximum exceeds the maximum relative heat
transfer from the analogous channel region with a spherical dimple by 1.4–1.5 times
Author:  S. A. Isaev, D. V. Nikushchenko, A. A. Klyus, A. Yu. Chulyunin, Dechai Kon
Keywords:  detached flow, narrow channel, inclined trench, spherical dimple, tornado-like vortex, heat exchange, numerical simulation
Page:  1293

INTERACTION OF METAL MELT FLOWS WITH A QUASI-SOLID FILM ON THE METAL SURFACE UPON A CHANGE IN THE AMPLITUDE OF AN ALTERNATING MAGNETIC FIELD

This work is devoted to induction melting of heat-resistant nickel alloys, in particular, to the problem of stability of
the oxidation film on the melt surface. The mathematical model describes heat and mass transfer in the metal melt
in an alternating magnetic field and elastically stressed states of the film on the melt surface. The main equations of
the problem and dimensionless parameters are presented. The states of the surface film are studied using numerical
simulation. It is shown how a change in the magnetic field strength affects the flow of the metal melt at different
frequencies. It is found that at different frequencies a change in the field strength leads to damping oscillations
in the velocity field. The causes of these oscillations are discussed in detail. Loading and destruction of thin films
during melt motion are considered. The mechanisms responsible for the primary destruction of the original film and
of its fragments are revealed. Rupture of a quasi-stable film at different frequencies is investigated. It is shown that
the result of the effect on the state of the film with an increase in the magnetic field strength depends on the field
frequency. A frequency range has been found in which the surface film is strong enough to prevent intensification of
the melt flow with increasing magnetic field strength. This effect ensures film stability
Author:  I. L. Nikulin, V. A. Demin, S. A. Nikulina
Keywords:  induction melting, surface cleaning, nonstationary flow, forced convection, Lorentz force, stress–strain state, film rupture
Page:  1298

METHOD OF ULTRASONIC CAVITATION SPRAYING OF LIQUIDS

A method is proposed for the ultrasonic cavitation spraying of liquid with an increased efficiency and with formation
of smaller-size droplets, compared to those provided by the known methods. The method proposed is based on
the formation of cavitation bubbles in the liquid kept under pressure and acted upon by ultrasonic vibrations.
A mathematical definition of the process has been developed and its critical parameters (the amplitude of the
ultrasonic vibrations and the hydraulic pressure) at which minimum-size droplets are formed were revealed. For
the practical realization of the method, a cavitation sprayer has been designed and the sizes of the droplets formed
were investigated depending on the parameters of the process. The cavitation sprayer designed provides, at an
ultrasonic vibration frequency of 24.3 kHz and a hydraulic pressure of 9∙10 ⁵ Pa, the formation of droplets of size
not larger than 45 μm. In this case, the rate of a liquid flow is smaller than 10 mL / s. For comparison, a known
method of ultrasonic spraying of liquid at a frequency of 22–24 kHz and the existing ultrasonic sprayers, working
at this frequency, give no way of forming droplets of size smaller than 100 μm
Author:  A. V. Shalunov, O. B. Kudryashova, S. A. Terentiev, V. N. Khmelev
Keywords:  ultrasound, cavitation spraying, liquid, dispersion, droplets
Page:  1310

USE OF THE METHOD OF GENETIC OPTIMIZATION FOR SOLVING PROBLEMS OF IDENTIFYING THE THERMOPHYSICAL PROPERTIES OF A MATERIAL

In creating mathematical models of the functioning of complex technical systems, one may often face a multilevel
hierarchy and structure of models. Such models, as a rule, include a large number of parameters characterizing
the process being described. The determination of these parameters is often associated with significant difficulties
or appears entirely impossible. This circumstance results from many factors: starting with the impossibility to
conduct direct measurements to the complexity of practical use of calculation algorithms. The paper discusses
a methodology developed to determine the thermophysical coefficients of a material based on a genetic method
of optimization. The genetic method makes it possible to construct a simple and efficient algorithm of solving a
coefficient inverse problem. The paper also presents the results of processing a model experiment on calculating
heat capacity and thermal conductivity coefficients
Author:  A. V. Netelev, I. A. Borisenko, M. O. Ivashinenko
Keywords:  calculation of thermophysical characteristics, genetic optimization, coefficient inverse problem, residual functional
Page:  1319

IDENTIFICATION OF THE CHARACTERISTICS OF THERMAL ENGINEERING MATERIALS UNDER CONDITIONS OF NONSTATIONARY HEATING AT VARIABLE PRESSURE BY SOLVING INVERSE HEAT TRANSFER PROBLEMS. 2. EXPERIMENTAL STUDIES

Characteristic of the space technology for ever were structures operating under conditions of intense, often ex-
treme, thermal effects since the general trend in the development of technology is associated with an increase in
the number of critical heat loaded technical objects with tightening the conditions of their thermal loading with a
simultaneous increase in reliability and service life, and a decrease in specific consumption of materials. For space
vehicles, moving in the atmosphere of planets, ensuring thermal conditions is one of the most important design and
development issues. Highly porous thermal insulation materials with low thermal conductivity are widely used in
the thermal protection structures of modern space technology objects. These materials, as a rule, have an open-
pore structure. This leads to the fact that the thermophysical properties of these materials depend significantly on
the gas pressure of the environment in which the heat protective structures based on them operate. It can also be
noted that as the ambient pressure increases, a more intensive increase in the thermal conductivity coefficient is ob-
served. The overall goal of this work is to develop a set of experimental and mathematical tools for a system of iden-
tification of the properties of highly porous materials operating under conditions of not only changes in thermal
loads, but also of a variable pressure. This part of the work is devoted to the experimental study of such materials
Author:  O. M. Alifanov, S. A. Budnik, A. V. Nenarokomov, D. M. Titov
Keywords:  highly porous materials, inverse heat transfer problems, iterative regularization method, thermal vacuum tests, temperature measurements, variable pressure
Page:  1329

CONJUGATE HEAT TRANSFER BETWEEN TWO PLATES WITH THE ANISOTROPY OF GENERAL FORM

A novel analytical solution has been formulated and obtained for the first time to the second initial boundary-val-
ue problem on conjugate heat transfer between two plates with the anisotropy of general form in both plates. The
generality of anisotropy means not only the presence of nonzero components of the thermal-conductivity tensors
of the plates, but also different orientations of the principal axes of the thermal-conductivity tensors; here, extra-
diagonal coefficients of the thermal-conductivity tensor may have arbitrary signs. Since the differential equations
of anisotropic thermal conductivity in both plates contain mixed derivatives of temperature with respect to space
variables, boundary conjugation conditions include all the components of the temperature gradient, even of the
boundary is plane. For this reason, the method of separation of variables would not do for solving equations with
mixed derivatives. Therefore, we have to use methods of Fourier and Laplace integral transformations accordingly
with respect to space variable and with respect to time. Here, in Fourier transforms, in the terms in the differential
heat-conduction equations containing mixed derivatives, there arise imaginary coefficients at the extradiagonal
coefficients of the thermal-conductivity tensor
Author:  V. F. Formalev
Keywords:  anisotropy of general form, components of the thermal-conductivity tensor, principal axes, temperature, heat capacity, heat conduction, conjugation conditions, conjugate heat transfer
Page:  1339

EXPERIMENTAL STUDY OF PHYSICAL SIMILARITY OF INTENSIFIED FREE-CONVECTIVE PROCESSES ON AIR-COOLED BUNDLES OF ROUND-RIBBED TUBES

Experimental studies of free-convective heat exchange of two-row bundles of bimetallic tubes with spiral rolled
aluminum ribs to vertical air flows created by an exhaust shaft 0.52 m high with an adjustable flow section of
0.0087–0.1185 m ² are presented. The staggered arrangement of the bundles was accomplished with an inter-
tube pitch of S _l = 70 mm from four tubes in a transverse row of the bundle. Based on the measurement data, the
average reduced heat transfer coefficient of the bundle was calculated, which amounted to a value from 1.26 to
3.84 W/(m ^2∙o C) at Rayleigh numbers (20–163)∙10 ³ .
It was found that the use of unheated half-tubes in the model of a ribbed bundle with an exhaust shaft can
lead to a significant violation of the physical similarity of the experiment. Moreover, the significance of this effect
increases with an increase in the rate of air flow through the bundle, i.e., at high values of the Rayleigh numbers
(Ra > 30,000) and optimum values of the coefficient of narrowing of the outlet opening area.
To ensure physical similarity of the experiment, it is recommended to use heated half-tubes in the model of
a ribbed bundle with an exhaust shaft or to provide at least six tubes in the transverse row of the bundle.
Author:  A. B. Sukhotskii, E. S. Danil′chik, G. S. Marshalova, D. V. Ostrovskaya
Keywords:  physical similarity, air-cooled ribbed tube bundle, free-convective heat exchange, exhaust shaft
Page:  1347

INCREASING HEAT TRANSFER EFFICIENCY OF HEAT EXCHANGING APPARATUS TUBES

An experimental rig made of silicate and brass tubes of a "double-pipe heat exchanger" type has been developed
to study the corrosion process and scale formation. Experimental studies have shown that the rates of corrosion
of silicate coatings of heat exchange tubes increase linearly with an increase in the speed of seawater move-
ment. It has been established that the rates of corrosion of silicate coatings of heat exchange tubes do not exceed
0.020 g / (m ² ·day). During long-term tests of silicate coatings of tubes, on the surfaces of the latter insignificant
scale deposits are formed, the thickness of which is within 0.14–0.23 mm, while on the metal surfaces of the tubes
a strong layer of scale and corrosion products with a thickness of 1.24–1.98 mm is formed. The conducted studies
have shown that in silicate coatings of heat exchange tubes the increase in the heat transfer coefficient is approxi-
mately 12–25%, depending on the operating conditions and the technological mode of the apparatus
Author:  N. Yu. Ibragimov, É. N. Ibragimli
Keywords:  heat exchange tubes, elevation of the efficiency, silicate coatings, corrosion rate, scale deposits, coating thickness, heat transfer coefficient, process mode, operating conditions of the apparatus
Page:  1354

APPROXIMATE-ANALYTICAL SOLUTION FOR HEAT REMOVAL FROM A SPHERICAL BODY IN THE GROUND

Regulation of the thermal regime of the soil in greenhouses assumes particular urgency in light of the need to
remove excess low-potential heat from thermal power plants. In this paper, a method for analytical calculation
of heat removal from a sphere immersed in the ground of a greenhouse is developed. Based on the calculation,
dependences of the specific heat flux are constructed on changes in the following parameters: ambient and soil
surface temperatures, depth of occurrence and diameter of the spherical body, coefficient of heat emission from
the ground surface to air, and thermal conductivity of the soil. This mathematical model can be used to predict the
temperature regime of the soil during subsoil heating
Author:  M. O. Utkin, N. D. Yakimov, V. V. Khar′kov, G. R. Badretdinova, A. V. Dmitriev
Keywords:  mathematical model, thermal regime, subsoil heating, greenhouse
Page:  1362

OPTIMALITY OF SOLVING A PROBLEM WITH A CONTROL GRADIENT IN THE COEFFICIENTS OF THE HEAT CONDUCTION EQUATION

Consideration has been given to the problem of optimal control with a control factor gradient in the coefficients of
the steady-state second-order heat conduction equation. The necessary optimality condition for solving this problem
is found. The application of the obtained results to the problem of controlling the domain boundary is indicated. An
example of instability of the considered problem is provided and an iterative algorithm of regularizing its solution
is described
Author:  R. A. Hamidov, M. A. Musayeva
Keywords:  optimal control, second-order steady-state heat conduction equation, necessary optimality condition, domain boundary control, ill-posed problems
Page:  1371

TOWARD THE METHODS OF DESIGNING A COMBINED SYSTEM "STIRLING ENGINE–ELECTRIC GENERATOR–LOAD (CONSUMER)"

Two known methods of modeling a free-piston Stirling engine are considered: in the first, the influence of the
electric generator is taken into account as a simple friction force in mechanics, while in the second, the generator
and its electric load are included in the model in an explicit form. Contrary to the current concepts, the results
obtained differ even at steady-state engine operation with identical frequencies. To get a reliable design of the
"Stirling engine–electric generator–load (consumer)" system, it is necessary to use an expression for the "friction"
force that depends on the electric current, i.e., modeling the current source and load is prerequisite, thereby making
it possible to take into account their inverse influence on engine operation. This is of fundamental importance, since
in practice the power of the consumer is often comparable to the power of the Stirling engine
Author:  K. O. Sabdenov, M. Erzada
Keywords:  Stirling engine, electric energy generation, distributed generation, efficiency
Page:  1380

METHOD OF PARAMETRIC IDENTIFICATION OF THE ORTHOTROPIC THERMAL-CONDUCTIVITY TENSOR OF 55G CARBON-FILLED PLASTIC AS A FUNCTION OF TEMPERATURE

The authors have presented an algorithm for parametric identification of thermomechanical characteristics of 55G
carbon-filled plastic in a cyclic single-step cryostat with its freezing to 2.6 K, that is intended to model the influence
of the factors of cosmic space on its thermophysical characteristics
Author:  N. O. Borshchev, M. I. Losev, L. A. Fedoseev, I. A. Belyaev
Keywords:  inverse heat-conduction problem, iterative-regularization method, cryogenic temperature, orthotropic tensor.
Page:  1390

FORCED CONVECTION HEAT TRANSFER OF COBALT NANOFLUID IN A GLYCEROL–WATER BASE MIXTURE

Heat-transmitting equipment is subject to growing operating temperatures and heat transfer rates, which leads to the
development of a nanofl uid as an alternative. The forced convection heat transfer coefficient (hn ) and friction factor
(fn) of cobalt (Co) nanofl uid in the glycerol–water (G/W) blends are reported in this work. A two-step procedure is
used to produce a co-nanofl uid of 0.18% maximum volume concentration in an optimal mix of 30% glycerol and 70%
water, and an experimental setup is constructed. The test segment is a simple circular copper pipe operating under
constant heat fl ux boundary conditions. The properties, concentration, and fl ow rate — all affect heat transfer in
nanofluids; the h n and f n of the nanofluid were higher than those of the basic fluid. At a 0.18% volume fraction and
similar Reynolds number, the maximum increase in h n and f n was 43.6% and 35.2%, respectively
Author:  T. Rajendra Prasad, K. Rama Krishna, K. V. Sharma, Nagesh Mantravadi, P. H. V. Sesha Talpa Sai
Keywords:  nanofluid, glycerol–water mixture, heat transfer coefficient, friction factor
Page:  1405

COMPREHENSIVE STUDY OF THE BIOCONVECTIVE FLOW OF A HYBRID NANOFLUID WITH GYROTACTIC MICROORGANISMS IN A SOLAR COLLECTOR

The three-dimensional flow of a hybrid nanofluid, including gyrotactic microorganisms, in a solar collector was
investigated for the purpose of improving its performance. The mathematical model of this flow was rearranged with
the use of the group transformation method into the model defined by ordinary differential equations. According
to the novel findings, the system of ordinary differential equations and the entropy generation were investigated
for the two values of the power-law index of the nanofluid: n = 2 and n ≠ 2. The influence of the parameters of the
hybrid nanofluid flow on its characteristics was analyzed on the basis of the graphs constructed. The two outputs
of the entropy generation were determined from the corresponding graphs for two different values of the power-law
index of the nanofluid. The numerical results obtained were compared with the analogous results of previous works
published. It was established that the velocity of flow of a hybrid nanofluid is strongly dependent on its power-law
index. Moreover, the percentage of increasing the Nusselt number of this nanofluid flow was predicted to be 28.18%
for the Prandtl number changing within the range (4 ≤ Pr ≤ 6)
Author:  A. S. Rashed, T. A. Mahmoud, A. E. Kabeel, S. M. Mabrouk
Keywords:  bioconvection, entropy generation, inclined configuration, group method, power-law index
Page:  1416

ON TEMPERATURE INHOMOGENEITY OF A REACTOR WITH AN ELECTROTHERMAL FLUIDIZED BED: CALCULATION OF A TEMPERATURE FIELD WITH ACCOUNT FOR JOULE HEAT SOURCES

The calculation of a temperature field in a bench-scale reactor with direct electric heating of a fluidized bed de-
signed for the synthesis and heat treatment of metal ceramic and carbon–graphite materials. The maximum tem-
perature difference in the working zone of the reactor with a diameter of ≈100 mm can reach 450 ^o C at a nominal
temperature of 1400–1500 ^o C. Such inhomogeneity is not typical of standard fluidized beds heated by an external
heater. The problem of inhomogeneity of the temperature field in the reactor with direct electric heating is related
to a significant localization of the current density and heat sources. Analysis has been made of the dependence of
temperature difference on the position of the central electrode. Measures have been proposed for the improvement
of the temperature field homogeneity in an electrothermal fluidized bed
Author:  O. S. Rabinovich, A. I. Malinovskii, A. A. Mikhailov
Keywords:  electrothermal fluidized bed, synthesis and heat treatment of materials, electric heating, temperature field, homogeneity, heterogeneous system, modeling
Page:  1429

FORMATION OF NITROGEN OXIDES IN A TWO-CHAMBER FLUIDIZED CYCLONE-BED FURNACE BURNING BIOFUEL PELLETS

Numerical modeling of nitrogen monoxide formation in a fluidized cyclone-bed furnace burning wood pellets was
performed for two temperature modes of furnace operation. Satisfactory agreement was obtained between the
calculated and experimental dependences of nitrogen monoxide concentrations on the excess air coefficient in the
exhaust gases
Author:  E. A. Pitsukha, Yu. S. Teplitskii, É. K. Buchilko, V. A. Dubina
Keywords:  cyclone-bed furnace, fluidized bed, nitrogen oxides, numerical modeling solid biofuel, nitrogen monoxide precursors
Page:  1436

CONCENTRATION FIELD OF THE TRACER IN A STRATUM WITH A HYDROFRACTURING CRACK

The authors have presented results on development of a mathematical model of convective evolution of a tracer
marker in natural reservoirs with a hydrofracturing crack with allowance for the leaks from the crack into the
stratum. To construct the pressure field as applied to two-dimensional problems, a quasi-stationary method has
been developed that uses the idea of successive change of steady states. To find the dimensions of the zone of
pressure perturbations in a porous medium, that is formed by the injection of the tracer into the crack, use has been
made of the law of conservation of mass. Dependences have been established of the velocity of motion of the tracer
marker in the hydraulic-fracturing crack and the surrounding porous medium on the parameters of the stratum and
the well.
Dependences have been constructed of the front and back boundaries and the length of the marker in the
crack and the surrounding porous medium on the reservoir parameters of the stratum and time. Formulas have
been determined to compute space–time concentration distributions of the tracer in the stratum with a crack.
On the basis of an analysis of the theory, regularities have been established of the formation of satellite markers
generated by tracer motion in the crack. It has been shown that in low-permeability reservoirs, the length of the
satellite marker is much smaller than its dimensions in the crack
Author:  A. I. Filippov, A. Yu. Davletbaev, R. R. Gareev
Keywords:  mathematical model, convection, tracer marker, concentration field, continuity equation, porous medium, hydraulic-fracturing crack
Page:  1447

ASSESSMENT OF THE PARAMETERS OF A FRACTURED-POROUS FORMATION BASED ON THE RESULTS OF THERMOHYDRODYNAMIC STUDIES OF VERTICAL WELLS

A mathematical model of nonisothermal filtration of liquid to a vertical well in a fractured-porous formation based
on a continuum approach and a computational algorithm for interpreting the results of thermohydrodynamic studies
of vertical wells have been developed. The results of test calculations using the proposed model and algorithm for
assessing the filtration and thermophysical parameters of the formation and the bottomhole zone using the pressure
and temperature measurements at the well bottom after the start-up are presented
Author:  M. N. Shamsiev, M. Kh. Khairullin, P. E. Morozov, V. R. Gadil'shina, A. I. Abdullin
Keywords:  fractured-porous formation, bottomhole zone, thermohydrodynamic studies, inverse problem
Page:  1458

NUMERICAL MODELING OF NATURAL AND CARBON DIOXIDE HYDRATE FORMATION DURING INJECTION OF THESE GASES INTO A SUBPERMAFROST WATER-SATURATED FORMATION

The article presents the results of a computational experiment aimed at obtaining criteria for selecting geological
structures for creating an underground natural gases storage facility and burial carbon dioxide in a hydrated
state in subpermafrost aquifier. A mathematical model of gas injection through a single well into a horizontal
water-saturated formation under permafrost rocks is presented, which takes into account all the main physical and
thermodynamic features of the hydrate formation process. A comparison of the calculation results for the dynamics
of distribution of temperature, pressure, water saturation, and hydrate saturation is carried out. Examples of
numerical calculation of gas injection into a formation with an initial water saturation of 0.9, porosity of 0.15, and
permeability of 8·10 ^–13 m ² are considered. The variable parameters are the volumetric flow rate of the injected gas
and equilibrium conditions of hydrate formation. The influence of the equilibrium conditions of hydrate formation
on the main indicator of the process efficiency — hydrate saturation of the created storage facility — is shown. The
results of laboratory experiments to determine the equilibrium conditions for the formation of hydrates of natural
and carbon dioxide gases in porous media and in aqueous solutions simulating formation waters of subpermafrost
horizons were used to conduct computational experiments. It was revealed that for the creation of an underground
storage facility, it is preferable to choose a formation with a sodium bicarbonate type of water, rather than with
fresh water
Author:  I. I. Rozhin, G. I. Ivanov
Keywords:  underground gas storage facility, natural gas, carbon dioxide, gas hydrate, hydrate formation, multiphase nonisothermal filtration, computational experiment
Page:  1465

MODELING OF NONLINEAR FILTRATION OF HIGH-VISCOSITY OIL UNDER HIGH-FREQUENCY ELECTROMAGNETIC INFLUENCE IN A WELL WITH A HYDRAULIC FRACTURING CRACK

The paper presents the results of numerical studies of nonlinear filtration of high-viscosity oil in an element of a
development system with four wells with hydraulic fracturing. In one of the wells, heated oil is extracted with a
staged high-frequency electromagnetic effect on the formation, and in the remaining wells, "cold" high-viscosity
oil is extracted. The distribution of pressure and temperature in the "wells–cracks–formation" system is simulated
with various pressure differences between the well and the formation, at various values of the initial pressure gra-
dient. The technology with a staged thermal effect was compared with the case of constant "cold" production of
high-viscosity oil
Author:  Z. S. Mukhametova, A. Ya. Davletbaev, L. A. Kovaleva
Keywords:  hydraulic fracturing crack, high-viscosity oil, nonlinear filtration, high-frequency electromagnetic field
Page:  1475

ASSESSMENT OF INSTRUMENTAL ERROR OF A CAPACITIVE MOISTURE METER

The main methods of measuring moisture content in the grain processing industry are considered. The main sources
of errors of the proposed digital grain moisture meter are identified. An assessment of the instrumental error of the
measuring part of the moisture meter is given
Author:  R. R. Kuluev
Keywords:  moisture content, error, grain, drying
Page:  1486

TWO-FREQUENCY ULTRASONIC TREATMENT FOR IMPROVEMENT OF THE EFFICIENCY OF PARTICLES′ COAGULATION IN SMOKE PRECIPITATION

An investigation has been made into the improvement of the efficiency of smoke precipitation by exposure of its
particles to ultrasonic vibrations. Results are presented for investigations into the effect on smoke precipitation
exerted by acoustic vibrations formed by two ultrasonic radiators operating at close frequencies compared to the
effect of two radiators operating at one frequency. A possibility has been established for substantial improvement
of the smoke precipitation efficiency by exposure of two radiators operating at one frequency. A two-frequency
effect on smoke ensured not only the formation of smoke particle agglomerates along the direction of propagation
of ultrasonic vibrations but also subsequent combination of agglomerates in the process of their rotational
movement under the effect of low-frequency vibrations (beating) occurring due to the interaction of ultrasonic
vibrations of different frequencies. A reduction in the energy expenditures on the process of smoke coagulation
compared to other methods of its precipitation should be considered as the advantage of smoke precipitation
under a two-frequency effect
Author:  V. N. Khmelev, A. V. Shalunov, S. N. Tsyganok, P. D. Danilov
Keywords:  smoke, precipitation, ultrasonic vibrations, ultrasonic effect (exposure), agglomeration, coagulation, disk emitter, sound pressure, piezoelectric ultrasonic oscillating (vibrating) system
Page:  1492

SYNTHESIS OF MOLYBDENUM BORIDES BY THE IMPACT OF AN A.C. ARC DISCHARGE IN AIR

The authors have pioneered in describing the method of obtaining molybdenum-boride crystalline phases through
the impact of an a.c. arc discharge on the starting mixture that contains molybdenum and boron powders in an open
air medium at atmospheric pressure. In the work, a study has been made of the dependences of the influence of the
regime parameters of an original arc reactor, such as the current strength of a power supply and the duration of
the arc discharge, on the phase composition of synthesis products. It has been established that during the treatment
of the starting mixture which contains molybdenum and boron powders in the atomic ratio Mo / B = 1 / 15 by an
atmospheric a.c. arc discharge for 50 s at a current strength of 300 A, a full processing of the starting components
to form molybdenum boride is ensured. The formation of the following molybdenum-boride crystalline phases has
been recorded: Mo ₂ B, α-MoB, MoB ₂ , and Mo ₂B ₅ . The obtained results allow extending the field of application of
a vacuum-free electric-arc method
Author:  Yu. Z. Vasil′eva, Yu. A. Neklya, M. Yu. Speranskii, A. Yu. Pak
Keywords:  vacuum-free method, arc discharge, alternate current (a.c), molybdenum boride
Page:  1501

SUBSCRIBE