Volume 97, №4
OPTIMUM INTERACTION OF THERMODYNAMIC SYSTEMS
Features of mathematical models of thermodynamic systems, typical formulations of problems on the optimum
control of them, and possibilities of using the indicated features in solving these problems were considered. Solutions
of the problems on the interaction of two subsystems exchanging scalar and vector fl ows of any nature in the process
of their direct contact or contact through a mediator have been found for any kinetics of these fl ows. Conditions of
minimum dissipation of the energy of a vector fl ow having a defi nite average rate were determined. Solutions of the
indicated problems defi ne the realizability boundary of a great number of regimes of thermodynamic systems.
Author:
A. M. Tsirlin
Keywords:
contact of thermodynamic systems, vector exchange fl ows, mediator, energy dissipation, rate of fl ows.
Page:
813-822
CALCULATING A SQUARED-OFF CASCADE BY THE METHOD OF VARIATION OF PARTIAL-FLOW CUTS
A method has been developed to calculate a squared-off cascade with an arbitrary number of external fl ows by varying
the cuts of partial fl ows of the stages and minimizing the deviations of the calculated feed fl ows of the stages from
specifi ed fl ows. To minimize the deviations of the fl ows, a honeybee-colony algorithm ensuring a required accuracy
in determining the parameters of the cascade was used. Based on a computational experiment on separation of
molybdenum hexafl uoride, the high effi ciency of the method for concentrating isotopes with an extreme mass number
has been shown.
Author:
V. A. Palkin
Keywords:
separation of isotopes, squared-off cascade, gas centrifuge, molybdenum isotopes
Page:
823-829
DESIGNING A SQUARED-OFF CASCADE FOR SEPARATION OF THE 92Mo AND 100Mo ISOTOPES TO HIGH PURITY
The separation of the 92Mo and 100Mo isotopes from the natural composition to the 99.99% enrichment level in a three-section squared-off cascade with 200 centrifuges was investigated. The parameters of this cascade were optimized using the 3SQC–PSO and 3SQC–GOA codes and the PSO and GO algorithms. The objective function of the indicated optimization codes is to simultaneously maximize the cascade capacity, the recovery factor, and the D-function. The results obtained show that the separation of the 92Mo and 100Mo isotopes should be done in two and one separation steps, respectively. A single cascade of most suitable confi guration for the separation of both the 92Mo and 100Mo isotopes is proposed. The recovery separations of the 92Mo and 100Mo isotopes in this cascade
comprise 92 and 95%, respectively.
Author:
S. L. Mirmohammadi, J. Safdari, M. H. Mallah, F. Ezazi
Keywords:
lightest and heaviest molybdenum isotopes 92Mo and 100Mo, three-section squared-off cascade, particle swarm optimization algorithm, Grasshopper optimization algorithm
Page:
830 - 843
COMPARISON OF THE PERFORMANCE OF THE OPTIMIZED SQUARED-OFF AND MATCH ABUNDANCE RATIO CASCADES TO SEPARATE LIGHTEST AND HEAVIEST MOLYBDENUM ISOTOPES TO 99.99%
The performance of the optimized three-section squared-off cascade is compared with that of a match abundance ratio cascade (MARC) for the enrichment of 92Mo and 100Mo isotopes from their natural composition to 99.99%. Two codes, namely, 3SQC–PSO and MARC–PSO, are developed for optimizing 200 centrifuge cascades using the particle swarm optimization (PSO) algorithms. The objective function is to maximize the cascade capacity, recovery factor, and the D-function and to minimize the total interstage fl ow. A comparison of the results shows that a MARC is able to enrich 100Mo with the highest recovery and production capacity. Due to the fact that more than one separation step is required for the separation of 92Mo, a MARC is beyond the capability to separate it to 99.99%, but a squaredoff cascade is capable of making this. Therefore, if the goal is the separation of all or some of isotopes of an element,
the squared-off cascade is the preferred option for economical industrialization and reducing installation.
Author:
S. L. Mirmohammadi, J. Safdari, M. H. Mallah, and Farzaneh Ezazi
Keywords:
lightest and heaviest molybdenum isotopes ( 92Mo and 100Mo), three-section squared-off cascade, match abundance ratio cascade (MARC), PSO algorithm
Page:
844-858
EXPERIMENTAL STUDY OF THE INFLUENCE OF THE NATURE OF A SURFACTANT ON THE DYNAMICS OF RISE OF A GROUP OF MONODISPERSE BUBBLES IN A LOW-VISCOSITY LIQUID
New results of experimental study of the process of rise of a spherically shaped group of monodisperse bubbles in
the presence of a surfactant in the region of Reynolds numbers Re = 200–600 have been presented. The infl uence of
the nature of a surfactant on the dynamics of rise of the group of bubbles has been analyzed. Experimental data have
been obtained on the trajectory of rise of bubbles forming the group depending on the type of surfactant in the liquid.
The authors were the fi rst to obtain experimental data on the velocity and the coeffi cient of resistance of a group of
monodisperse bubbles rising in the presence of diff erent surfactants. Criterial dependences have been obtained for
dimensionless velocity of rise of a group of monodisperse bubbles as a function of the type of surfactant in the liquid
Author:
V. A. Arkhipov, A. S. Usanina
Keywords:
group of bubbles, surfactant, nonviscous liquid, coeffi cient of resistance, intermediate regime, experimental study.
Page:
859-868
CARRY OF DISPERSE-ADMIXTURE PARTICLES BY A VORTEX RING
A numerical simulation of the gasdynamic processes accompanying the formation and propagation of vortex rings
obtained with the use of a piston-type generator has been performed. The formation of a vortex ring, the capture of
particles of a disperse admixture by it, and their carry by the ring are considered. The numerical calculations were
conducted with the use of nonstationary Navier–Stokes equations, and the movement of particles was defi ned using
the discrete-trajectory method. The distribution of the admixture particles in a vortex ring was determined depending
on the conditions of its formation. The infl uence of the characteristics of a vortex ring on the carry of a passive
admixture by it was investigated. The reasons for the qualitative and quantitative diff erences between the losses of
particles in a vortex ring in the path of its movement in diff erent regimes are discussed
Author:
K. N. Volkov, V. N. Emel′yanov, I. E. Kapranov
Keywords:
computational gas dynamics, vortex dynamics, vortex ring, particles, two-phase fl ow
Page:
869-876
INFLUENCE OF SURFACTANTS ON CONTACT ANGLE AND FLOTATION SEPARATION OF POLYBUTYLENE TEREPHTHALATE AND ACRYLONITRIL BUTADIENE STYRENE
A technique has been proposed for measuring the contact angle of plastics, which makes it possible to determine the degree of wettability of their surface, on the basis of which assumptions can be made about the applicability of surfactants as wetting agents in the process of fl otation separation of a mixture of plastics. The eff ect of aqueous solutions of surfactants on the contact angle and effi ciency of fl otation separation of a mixture of polybutelene terephthalate and acrylonitrile butadiene styrene was studied. The wettability of the surface of these plastics with aqueous solutions of sodium laureth-3 sulfosuccinate, sodium lauryl sarcosinate, polysorbate 80, and C8-C14 alkyl polyglucoside with a concentration of 2∙10–3–0.01 g/dm3
was determined. It has been found that the wettability of
the surface of plastics with aqueous solutions of surfactants and the effi ciency of fl oation separation of a mixture of
plastics depend on the type of surfactants and their concentration in the aqueous solution.
K
Author:
A. A. Kovaleva, P. S. Kulevets, A. É. Levdanskii
Keywords:
plastics, sorting, fl otation, contact angle, surfactants
Page:
877-884
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF THE ISOTHERMAL STRATIFICATION OF A POLYDISPERSE EMULSION WITH THE USE OF THE QUASI-MONODISPERSE APPROACH
An experimental investigation and a mathematical simulation of the gravitational stratifi cation of a polydisperse
water–oil emulsion in a rectangular cell have been performed. Histograms of the size distribution of droplets in the
initial emulsion have been obtained using the approach based on the analysis of the images of an emulsion sample,
made on an optical microscope at diff erent magnifi cations. The concentration distributions of droplets along the
height of the cell have been constructed using results of the digital processing of the photos of the emulsion, obtained
in the experiment on its gravitational stratifi cation. A methodology of numerical simulation of the stratifi cation of a
polydisperse emulsion system, based on the representation of this system as a set of quasi-monodisperse subsystems
and on the combined solution of the equations for the sedimentation of droplets diff erent in size in the one-liquid
approximation, is proposed.
Author:
A. A. Musin, V. I. Valiullina, R. R. Yulmukhametova, L. A. Kovaleva
Keywords:
polydispersity, emulsion, droplets, quasi-monodisperse approach, mathematical simulation, experimental investigation
Page:
885-894
UNSTEADY PRESSURE FIELD IN A POROUS BED WITH A WEAKLY COMPRESSIBLE FRAMEWORK IN NONLINEAR RADIAL FILTRATION OF FLUID IN IT
Consideration has been given to a nonlinear problem of a fi ltration pressure fi eld in a porous bed operated in a
specifi ed depression regime with a one-dimensional radial fl ow of a compressible medium in it. Solutions have been
obtained of a problem for the zeroth and the fi rst expansion coeffi cients of a nonlinear fi ltration pressure fi eld, which
represent the main and the fi rst asymptotic approximations describing high-amplitude pressure fi elds in oil and gas
beds with a weakly compressible framework. The development of the asymptotic method as applied to the problem
under consideration has led to the creation of a new method of constructing analytical expressions for expansion
coeffi cients, which coincides with the method of succession of steady states in solving the problem for the leading
approximation. Based on a computational experiment, it has been shown that the pressure fi eld in a porous bed with
a weakly compressible framework is most accurately described using the method of succession of steady states, according to which pressure disturbances in the bed are absent at short times. It has been established that with increase
in the distance from the well axis the disturbance delay time increases, and the velocity of the buildup of perturbations, caused by the operation of the well in a constant depression mode, decreases.
Author:
A. I. Filippov, M. A. Zelenova, O. V. Akhmetova
Keywords:
fi ltration, nonlinearity, asymptotic method, steady state, quasi-stationary state, piezoconductivity equation.
Page:
895-905
SPECIFIC FEATURES OF THE FORMATION OF SULFUR DIOXIDE HYDRATE IN A POROUS BED CONTAINING METHANE AND WATER IN THE INITIAL STATE
The paper presents a mathematical model of injecting liquid sulfur dioxide in a porous bed saturated with methane and water in a fl at-dimensional approximation. The formulation of the problem under consideration implies the formation of SO2 hydrate on the frontal surface separating the region saturated with sulfur dioxide and its hydrate and also with methane and water. An investigation has been made into the eff ects of the pressure and temperature of the sulfur dioxide being injected, of the initial temperature and also of the permeability of the system on the specifi c features of the formation of SO2 hydrate. Based on numerical calculations, it has been shown that in the case of low injection pressure values, the formation of sulfur dioxide hydrate can occur in a regime with the formation of an additional region containing methane and its gas hydrate. It has also been shown that in the case of high values of injection temperature and of the bed′s initial temperature, and also of the bed permeability, the formation of sulfur dioxide hydrate occurs without the formation of a region containing methane and its gas hydrate. The critical injection temperature whose exceedance results in the occurrence of a regime without the formation of a region containing methane and its gas hydrate has been shown related to the SO2 injection pressure. Based on the analysis
of this dependence, it has been shown that the regime with the formation of a region saturated with methane and its
gas hydrate is characteristic of the case of low injection temperature and pressure values.
Author:
M. V. Stolpovskii, I. K. Gimaltdinov
Keywords:
porous bed, phase transition, gas hydrate, sulfur dioxide, methane
Page:
906-913
MODELING GRANULE CONSOLIDATION DURING ELECTRICAL HEATING
The paper presents a numerical discrete element model of granule consolidation taking into account only the elastic
interaction force. Calculation of electric and temperature fi elds was added to the model. Granules are considered as
a set of nodes with links in between. Using this model, numerical experiments were carried out, the results of which
qualitatively show the process of granular material consolidation.
Author:
V. V. Krizhanovskiy, A. G. Anisimov, and É. R. Pruuel
Keywords:
consolidation, electric heating, granule
Page:
914 - 924
REVEALING AND STUDYING OF THE MECHANISM OF MOISTURE REMOVAL FROM MATERIALS ON EXPOSURE TO ULTRASONIC NONCONTACT EFFECT
The article is devoted to the study of the process of removing moisture from capillary-porous materials by its
dispersion during the collapse of cylindrically-shaped cavitation bubbles formed in the capillaries of the material
under ultrasonic exposure. A model has been proposed and developed that made it possible to explain the mechanism
of dispersion during realization of the life cycle of a bubble in a capillary — slow growth, rapid expansion with
deformation, and subsequent collapse. The range of sound pressure levels at which dispersion begins (from 150 dB)
to the level at which bubbles reach the size of the capillary and the increase in the drying effi ciency stops (170 dB)
has been determined theoretically. It was also shown that for maximum effi ciency in moisture removal, the size of the
dehydrated sample must correspond to the ultrasonic wavelength in air. The mechanism of ultrasonic dispersion of
liquid during drying has been confi rmed experimentally and it has been established that to reduce the drying time
by more than 40%, exposure with a level in the range of 165–170 dB is necessary, and the dried materials must be
placed in the form of particles or layers having dimensions or thicknesses corresponding to the ultrasonic wave
length. The practical implementation of ultrasonic drying using the example of food products (red beets) confi rmed
the eff ectiveness of the proposed mechanism and ensured a reduction in drying time by 1.9 times on reducing energy
demand by 1.6 times.
Author:
V. N. Khmelev, A. V. Shalunov, S. A. Terent′ev, R. N. Golykh, and V. A. Nesterov
Keywords:
drying, energy effi ciency, ultrasonic vibrations, dehydration, intensifi cation, dispersion
Page:
925 - 937
DEFORMATION OF DROPLETS AND BUBBLES IN RHEOLOGICAL FLUIDS
The authors have proposed diff erent models of deformation of droplets and bubbles in regular and non-Newtonian
fl uids depending on Weber, Morton, and Reynolds numbers. Consideration has been given to a geometric
interpretation of the issues of deformation with the aim of evaluating the surface and volume of a deformed droplet.
The infl uence of asphalt and resin material contained in heavy oils on the degree of deformation of the droplets in
them has been evaluated. Models of deformation of droplets and bubbles in regular and non-Newtonian fl uids have
been developed. It has been noted that the change in the shape of droplets in heavy oils is slight owing to their high
viscosity. A comparison of the proposed models of deformation of droplets with the existing experimental data and
with other models has been made.
Author:
G. I. Kelbaliyev, S. R. Rasulov, M. R. Manafov, and F. R. Shykhyevaa
Keywords:
droplets, bubbles, deformation, ellipsoid, heavy oils, rheology, asphalt and resin materials, eff ective viscosity, surface tension
Page:
938 - 946
NEW VIBRATION VISCOMETER FOR MEASURING THE VISCOSITY OF LIQUIDS
A new vibrating plate viscometer has been developed which is used and makes it possible to instantly and continuously
measure the viscosity of a high-temperature material. This viscometer is designed for industrial use and enables one
to measure the viscosity automatically to a high accuracy. This method of measuring the viscosity is currently used
in various fi elds, such as the study of newly produced oil products, the selection of the optimal fl ow characteristics
for various transfer conditions, and the development and improvement of preparing fuels
Author:
J. Shamuratov, I. Ruziev, M. Ismoilov, A. Boltoyev
Keywords:
vibration, viscosity, amplitude, frequency, thickness, resonation.
Page:
947-955
THEORETICAL AND EXPERIMENTAL DETERMINATION OF THE RATE CONSTANT OF THE NONADIABATIC CHEMILUMINESCENT REACTION H + O + N2 = OH* + N2
The electronically nonadiabatic reaction of preassociation H + O + N2 ↔ OH* + N2 is the main channel of formation of electronically excited chemiluminescent OH* molecules during the oxidation of hydrogen in mixtures with a high content of nitrogen, e.g., during the combustion of hydrogen in air. For this reaction, within the framework of the combined theoretical and experimental approach with the use of the earlier results of quantum-chemical calculations for the rate constant of the elementary process H + O → OH* in the limit of high pressures and experimental data on OH* glow in N2-diluted H2/O2 mixtures (including those obtained in this work), a physically substantiated dependence of the rate constant on temperature and pressure has been obtained for a broad range of thermodynamic parameters (T = 200–4000 K and p = 10–3–102
atm). It has been shown that the found rate constant is in reasonable agreement with the existing results of measurements in both shock tubes and fl ames, with the rate constant in the process under study in a nitrogen buff er gas (M = N2) turning out to be nearly 1.3–1.8 times lower (at atmospheric
pressure) than for M = Ar. It has been noted that in interpreting measurements of the temporal intensity profi les of
OH*
emission collected from the entire combustible volume (from the end of a shock tube), taking account of the
self-absorption of emission on combustion products is substantial
Author:
B. I. Lukhovitskii, A. S. Sharipov, I. V. Arsent′ev, A. V. Pelevkin, A. V. Skilond′, Yu. S. Kisel′, P. N. Krivosheyev
Keywords:
hydroxyl radical, electron excitation, chemiluminescence, preassociation, nitrogen, shock tube, diagnostics of combustion
Page:
956-967
STUDY OF THE OCCURRENCE OF STEADY VIBRATING COMBUSTION AND ITS ADVANTAGES
The physical characteristics of solid biofuel under combustion in a Rijke tube installation have been studied. A
decrease in the fl ame temperature and an increase in the heat fl ux density on the tube wall on the occurrence
of vibrating combustion were detected. To study vibrating combustion under conditions close to practical use in
power plants, experiments were carried out on a "container–tube" type installation. The optimal parameters of the
installation for the implementation of vibrating combustion of solid biofuels were obtained. A theoretical model
of the development of sound disturbances of a combustion wave has been developed and its infl uence on heat
transfer characteristics has been elucidated. An empirical-theoretical relationship has been obtained for calculating
heat transfer in a Rijke tube during vibrating combustion. A model is proposed for calculating the amplitude of
disturbances for instabilities in "container–tube" installations.
Author:
V. D. Geshele and I. P. Raskatov
Keywords:
vibrating combustion, fl ame temperature, solid fuel, heat fl ux density, acoustic radiation power, installations of the Rijke tube and container–tube types.
Page:
968 - 972
MATHEMATICAL MODEL OF CALCULATION OF THE SURFACE INTENSITY OF FEED OF A COOLANT IN AVIATION EXTINGUISHING OF GROUND FOREST FIRES
Results of mathematical modeling of the water concentration of the underlying surface during the aviation
extinguishing of ground forest fi res of varying intensity have been given. In extinguishing a high-intensity ground
fi re, droplets entering the zone of combustion evaporate in the fl ame. Therefore, no wetting of the underlying surface
occurs in the combustion zone. With increase in the initial velocity of the droplets, the left boundary of the zone of
wetting shifts to the seat of fi re, thus raising the effi ciency of the use of water in the process of fi re extinguishing. In
extinguishing a moderate-intensity ground fi re, two coverage zones are formed on the windward and leeward sides of
the seat of fi re, and also the region of intense evaporation between them. Boundaries between these regions are only
determined by the intensity of the fi re and by the geometric characteristics of the combustion zone. Investigation of
the infl uence of conditions for the formation of a gas–droplet cloud on the process of extinguishing a low-intensity
ground fi re shows that at a small dropping height, a single continuous coverage zone is formed. In this case its length
is determined mainly by the length of the primary cloud and to a lesser extent by the initial droplet velocity and the
distribution of the wind velocity in the atmosphere.
Author:
O. V. Matvienko, V. A. Arkhipov, O. I. Daneiko, A. S. Usanina, S. A. Basalaev, A. M. Bulavk
Keywords:
aviation fi re extinguishing, liquid–droplet cloud, gravity sedimentation, high-temperature medium, natural fi re, breakup and evaporation of droplets, mathematical modeling.
Page:
973-984
DETERMINATION OF THE CATALYTIC ACTIVITY OF THE MXene IN THE COMBUSTION OF AMONIUM PERCHLOTRATE
The catalytic decomposition of a Ti3C2–ammonium perchlorate composite was investigated. The elemental and
structural properties of the MXene were determined using the scanning electron microscopy, and its catalytic
activity in the combustion of the ammonium perchlorate was estimated on the basis of the DTA and TGA data. It
was established that the MXene exhibits an excellent reactivity and substantially infl uences the temperature of the
ammonium perchlorate in the fi rst and second exothermic periods of its decomposition and, consequently, the kinetic
parameters of this decomposition.
Author:
Zh. Korkembay, K. Toshtay, M. Atamanov, F. Malchik, R. Amrousse, Y. Merkibayev, A. Imash, Z. Mansurova,
Keywords:
ammonium perchlorate, decomposition, MXene, kinetic parameters, catalytic activity
Page:
985-992
ANALYSIS OF THE INFLUENCE OF SILICON DIOXIDE NANOPARTICLES ON THE RHEOLOGY OF XANTHAN GUM SUSPENSIONS
The eff ect of silicon dioxide nanoparticles on the rheology of aqueous solutions of xanthan gum was studied. Tests
were carried out on a rotational viscometer and by the oscillatory method on an Anton Paar rheometer. Additions
of nanoparticles up to 2 wt.% to solutions containing up to 1 wt.% gum were analyzed. In the studied concentration
ranges, the infl uence of nanoparticles maintains the shape of the fl ow curves and viscosity curves, introducing small
changes. It was shown that with increasing concentration of nanoparticles, the elastic modulus of suspensions, the
values of their yield strengths and fl ow points increase. At the same time, the pseudoplasticity index practically
does not increase, leading to the manifestation of a brittle rupture with increasing load in the oscillatory test of
the suspension. The storage modulus at a nanoparticle concentration of 1% takes on a two-stage form, and at a
concentration of 2% it forms a hysteresis curve, indicating a brittle rupture of the material. It was shown that the
eff ect of the conformational transition is about 30% and decreases with increasing fl ow shear rate.
Author:
V. V. Syzrantsev, Z. Sh. Gatsaev, S. S. Viskhanov
Keywords:
nanofl uid, xanthan gum, yield strength, fl ow point, nanoparticles, drilling fl uid
Page:
993-1000
METHODS OF DECREASING THE MAXIMUM SURFACE TEMPERATURES OF BODIES MADE OF COMPOSITE MATERIALS IN THE CASE OF HYPERSONIC FLOW AROUND THEM
The hypersonic fl ow around bodies of diff erent geometries, made of composite materials, was investigated and
diff erent methods of decreasing the maximum temperatures of their surface were estimated.
Author:
V. I. Zinchenko, V. D. Gol′din
Keywords:
hypersound, thermal shielding, conjugate heat exchange, heat-shield materials, trajectory movement conditions
Page:
1001-1008
AN EXAMPLE OF AN ACCURATE SOLUTION OF A PROBLEM ON STRATIFIED FLOWS CAUSED BY SPATIAL INHOMOGENEITIES OF TRANSFER COEFFICIENTS
In the recent literature, attention has been drawn to the previously uninvestigated mechanism of the occurrence of
fl ows in a stratifi ed fl uid in a gravity fi eld. Such fl ows can occur in the absence of pulse and buoyancy sources due
to horizontal inhomogeneity of transfer coeffi cients. For the fi rst time, this investigation provides an example of an
exact analytical solution of such a problem free from assumptions of amplitude smallness.
Author:
L. Kh. Ingel′
Keywords:
stratifi ed media, inhomogeneous transfer coeffi cients, gravity fl ows, accurate analytical solution
Page:
1009 - 1011
INFLUENCE OF THE ANGLE OF ATTACK OF A PLATE LOCATED IN THE TURBULENT BOUNDARY LAYER ON SKIN FRICTION
The author has presented results of numerical modeling of the infl uence of the angle of attack of a thin width-limited plate with a short chord on the velocity fi eld of the internal region of a turbulent boundary layer (TBL) and skin friction. The computations were performed by the large eddy simulation (LES) method at the Reynolds number Reθ = 540 calculated from the velocity on the channel axis and the momentum thickness. Changes in the average and pulsation characteristics of the three-dimensional velocity fi eld under the impact of the wake of the plate and of tip vortices as functions of the angle of attack of the plate in the range ±1o
have been analyzed. It has been shown
that a determining infl uence on the formation of the velocity fi eld is exerted by the tip vortices whose vorticity is
opposite with the positive and negative angles of attack. The mean value of the skin-friction coeffi cient decreases
by 6% at the positive angle of attack and by 14% at the negative angle with respect to the value of this coeffi cient in
an unperturbed TBL.
Author:
V. L. Zhdanov
Keywords:
turbulent boundary layer, velocity field, skin friction, vortex generator, wake, tip vortices, LES
Page:
1012 - 1026
SIMULATION OF FLOW STRUCTURE BY VELOCITY PROFILE
It is proposed to determine the main parameters of the structure of fl ows in objects by velocity profi le without
taking response curves using the indicator method in heat and mass transfer apparatuses and reactors. A formula
is derived for calculating the variance (central moment of the second order) and the fl ow structure function for
a half-open vessel. An algorithm is also proposed for calculating the average residence time, the Peclet number
of longitudinal diff usion for a one-parameter diff usion model, the number of cells and the diff erential response
function of a combined model with a sequential connection of ideal displacement and mixing zones for a cell model.
Moreover, calculation of the distribution density of the diff erential and integral response curves corresponding to a
given velocity profi le is provided.
Author:
A. B. Golovanchikov, K. V. Cherikova, N. A. Prokhorenko, N. A. Merentsov
Keywords:
fl ow structure, velocity profi le, response curve variance, average residence time, Peclet number of longitudinal diff usion, number of cells, distribution density, diff erential and integral response functions
Page:
1027- 1033
A SIMPLE MODEL OF STIRLING MACHINE (ENGINE) WITH FREE WORKING PISTON
Regenerator in the Stirling engine is the most important element; the equation of momentum conservation has been proposed for the mass of gas in it. This makes it possible to take into account relaxation hydrodynamic processes in the regenerator and, as a consequence, the model is simplifi ed greatly. The simulation was carried out in the isothermal approximation. In the engine, at the initial stage, high-frequency (~102
Hz or more) and low-frequency
oscillations (~10 Hz or less) originate. The movement of the working piston and displacer corresponds to low
frequency vibrations. Without relaxation processes in the regenerator, the Stirling engine does not work. There is
a minimum temperature diff erence between the heater and cooler, below which a free-piston engine also does not
operate, but can operate like another type of Stirling engine.
Author:
K. O. Sabdenov
Keywords:
Stirling machine with a free working piston, regenerator, thermodynamic Stirling cycle
Page:
1034 - 1041
EXPERIMENTAL INVESTIGATIONS INTO THE HEAT TRANSFER OF A STANDARDIZED BIMETAL ANNULAR-FINNED TUBE WITH VARIOUS HEIGHT OF THE FINS UNDER THE CONDITIONS OF FREE AIR CONVECTION
The paper presents a generalization of the results of an experimental investigation into the heat transfer of a bimetal fi nned tube with spiral knurled annular fi ns (interfi n pitch s = 2.5 mm) under the conditions of free convection.
The obtained results were approximated using two options for selecting defi ning characteristics to calculate similarity numbers, viz., the West European variant, where the interfi n space s′ is taken as a characteristic dimension and the wall temperature tw is taken as a defi ning temperature, and the East European variant, where the fi n baselimited tube diameter d0 is taken as a characteristic dimension and the air temperature inside the chamber t0 is taken as a defi ning temperature. It has been established that in tubes with narrow fi nning, free-convection heat transfer is represented with better quality by the criterial equations of the East European variant.
A similarity equation has been obtained for calculating the average reduced heat transfer of a single fi nned tube with various fi n height h = 0–14.6 mm at diff erent angles of the tube inclination γ = 0–90o
to the horizontal plane at the Rayleigh number Ra = (32–450)·103
. A heat fl ux optimal fi n height (hef = 10.8–12.3 mm) has been
determined that decreases with increase in the angle of inclination.
Author:
E. S. Danil′chik, A. B. Sukhotskii,G. S. Marshalova, D. V. Ostrovskaya
Keywords:
free convection, bimetal annular-fi nned tube, methods for selecting a characteristic dimension and a defi ning temperature of similarity numbers, Nusselt number, Rayleigh number, generalizing equation, optimum fi nning height, tube inclination angle
Page:
1042 - 1049
DETERMINATION OF HEAT AND MASS EMISSION COEFFICIENTS IN A HYBRID COOLING TOWER WITH TRANSVERSELY FINNED RADIATOR PIPES
A hybrid cooling tower, which is a promising type of coolers, can be used successfully to cool the circulating water
of industrial enterprises taking into account the modern requirements for energy effi ciency, resource saving, and
environmental friendliness. A hybrid cooling tower design has been developed including a sprinkler made of inclined
corrugated contact elements and an internal fi nned tubular radiator. The purpose of the work is to experimentally
determine the volumetric coeffi cients of heat and mass emission in the developed hybrid cooling tower for cooling
circulating water. A diagram of an experimental installation of a cooling tower with hybrid cooling system is presented
and described. Graphic dependences were constructed for the volumetric coeffi cients of mass emission and heat
emission on the average fl ow rate of cooling air at various wetting mass densities. A dimensionless equation has
been obtained for determining the volumetric coeffi cients of mass emission in a hybrid cooling tower with transverse
fi nning of radiator pipes. A comparison of volumetric coeffi cients of mass emission for the developed cooling tower
with other water-cooling devices showed the potential of its usage for cooling circulating water, especially at high
ratios of gas and liquid phase loads.
Author:
I. N. Madyshev, V. V. Khar'kov
Keywords:
heat and mass exchange, cooling, circulating water, cooling tower, tubular radiator, fi nning
Page:
1050 - 1057
THE PROCESS OF HEAT EXCHANGE IN A CHIMNEY STACK ON COOLING EXHAUST GASES BELOW THE DEW POINT
A mathematical model and a program for calculating heat exchange in a fl ow of combustion products cooled below
the dew point in a condensation heat exchanger, in a gas exhaust pipe with a clamp lining have been created.
Analytical dependences are presented making it possible to determine the temperature of the exhaust gases, as
well as temperature fi elds and thermal stresses in the wall of the gas exhaust pipe depending on the proportion of
bypassed uncooled gases, thermophysical characteristics of the materials of the pipe wall and combustion products,
geometric parameters of the pipe, and the intensity of the impact of environment on it. Calculations of the processes
of heat exchange of gases moving in a reinforced concrete chimney were carried out for the case of its protection
from hydrate corrosion by the bypass method. It has been established that for a three-layer reinforced concrete
chimney with a height of 180 m, the quantity of bypassed gases is 30–35% of the total amount of gases. If there is
a condensing heat-utilization unit in the boiler plant, the temperature diff erence in the gas exhaust pipe, its free
thermal deformation and thermal stresses in the structural elements of the pipe are reduced by 2.12–2.99 times,
which increases the reliability of the pipe.
Author:
A. A. Kudinov, S. K. Ziganshina
Keywords:
boiler plant, combustion products, chimney, condensation heat exchanger, hydrate corrosion, dew point, bypassed gases, temperature fi elds, thermal stresses
Page:
1058 - 1067
LASER SPARK-FREE INITIATION OF A SUBCRITICAL MICROWAVE DISCHARGE
Experimental study has been made of the ignition of a subcritical microwave discharge at pressures in the range
55–79 Torr with the initiation by pulsed laser radiation (58 mJ in a pulse). A rise of 36% in the critical pressure
was obtained to form the discharge with the orientation of the laser beam along the vector of the microwave-fi eld
strength. Computer modeling has shown that upon the traversal of a focused laser beam, a highly conductive laser
trail can be formed with a peak ionization degree as high as 10%, which, for a period of the order of 1 μs, locally
enhances the electric microwave fi eld up to supercritical values.
Author:
Yu. V. Dobrov, V. A. Lashkov, I. Ch. Mashek, A. M. Prokshin, M. E. Renev, R. S. Khoronzhuk
Keywords:
microwave discharge, laser radiation, plasma, subcritical discharge, experiment, numerical modeling
Page:
1068 - 1081
LASER-INDUCED EVAPORATION OF METAL FILMS
Nanofi lms of zinc, aluminum, lead, silver, and copper have been obtained by the laser-plasma method. The conditions
of deposition of such fi lms on substrates, providing the absence of metal particles on their surface, were determined.
The threshold power densities of the laser radiation acting on a metal target, at which an intense evaporation of
its material begins, were found experimentally. It is shown that the boiling temperature of the material of a target
infl uences the surface relief of the metal nanofi lms obtained. The conditions of obtaining fi lm coatings with small
particles of the target material on their surface, which can be used for the realization of the giant Raman scattering,
were determined.
Author:
V. K. Goncharov, G. A. Gusakov, M. V. Puzyrev
Keywords:
laser-plasma method, nanodimensional metal fi lms, erosion laser plasma
Page:
1082 - 1090
EXACT NONINTEGRAL FORMULA FOR THE BLOCH–GRÜNEISEN DEPENDENCE OF THE CONDUCTIVITY OF METALS ON TEMPERATURE
An exact explicit nonintegral expression is obtained for the Bloch–Grüneisen formula, which describes the specifi c
lattice resistance of pure metals and contains polylogarithms. A formula is given for a special case of the obtained
expression — the exact formula of a metal transistor
Author:
A. E. Dubinov
Keywords:
Bloch–Grüneisen formula, exact expression, polylogarithm, resistance of pure metals, thermistor formula
Page:
1091 - 1093