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Thermophysics and Aeromechanics

2015 year, number 4

Methods of magnetic fluid synthesis (review)

S.A. Novopashin, M.A. Serebryakova, and S.Ya. Khmel
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: magnetic fluid, colloid solution, nanoparticles in carbon coating
Pages: 397412

Abstract >>
This is a review of the current state of research in the field of the methods of magnetic fluid synthesis. It focuses on analysis of the methods that use magnetic nanoparticles in an inert coating.



Control of turbulent boundary layer through air blowing due to external-flow resources 

V.I. Kornilov, A.V. Boiko, and I.N. Kavun
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: control, turbulent boundary layer, plate, intake, finely perforated surface, blowing, skin friction
Pages: 413426

Abstract >>
The possibility to control turbulent incompressible boundary layer using air blowing through a finely perforated wall presenting part of the streamlined flat-plate surface was examined. The control was exercised via an action on the state and characteristics of the near-wall flow exerted by controlled (through variation of external-pressure-flow velocity) blowing of air through an air intake installed on the idle side of the plate. A stable reduction of the local values of skin friction coefficient along the model, reaching 50 % at the end of the perforated area, has been demonstrated. The obtained experimental and calculated data are indicative of a possibility to model the process of turbulent-boundary-layer control by air blowing due to external-flow resources.



The effect of slot height and difference in gas densities for coaxial jets on jet mixing in constrained swirled flow 

N.E. Shishkin
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: swirled gas film cooling, gas concentration at wall, nonisothermal flows, constrain factor
Pages: 427433

Abstract >>
Experiments were conducted about the effect of height of annular slot on efficiency of film cooling in a tube flow. Nonisothermal nature of flows was modelled by mixing of jets with different densities: air with argon or with helium: the concentration of foreign gas on wall was measured. The influence of nearwall jet swirling and of proportions of densities of gas flows as key factors for laminarization of mixing was considered.



The model of heat and mass transfer in rough and irrigated ducts

A.G. Laptev and E.A. Lapteva
Kazan State University of Power Engineering, Kazan, Russia
Keywords: heat transfer, mass transfer, skin friction, roughness, film, coolers, analogy
Pages: 435440

Abstract >>
To determine the coefficients of the heat and mass transfer in the ducts with rough and irrigated walls the de-velopment of the classical hydrodynamic analogy of the momentum, mass, and energy transfer has been continued. The conservation properties of the skin-friction laws with respect to various disturbances are used for this purpose, and the effective velocity is found the value of which enables us to correct the hydrodynamic analogy. The examples of computations of the Nusselt, Sherwood, and Stanton numbers are shown for rough ducts, cooler, and film flow in the counter-flow. A comparison with the results of other researchers is given.



Fluctuation emergence of bubbles under a rapid drop of pressure in a liquid

P.A. Pavlov and V.E. Vinogradov
Institute of Thermophysics UB RAS, Ekaterinburg, Russia
Keywords: cavitation, extension, homogeneous nucleation, heat flux
Pages: 441452

Abstract >>
Explosive cavitation at the front of a negative-pressure pulse has been studied. Conditions for the emergence of bubbles by the mechanism of homogeneous fluctuation nucleation were identified. Those conditions feature a high rate of the phase transformation, with the vapor formation process being concentrated in time at the instant of attainment of a certain pressure. Under such conditions, the liquid cavitation strength is maximal, and its value can be predicted by the homogeneous nucleation theory. For implementing the regime with high nucleation frequency, a method based on passing a negative-pressure pulse across a region with locally heated liquid was employed. The cavitation kinetics was examined by monitoring the perturbation of the heat flow from a miniature heater. The experimental data were generalized using the theory of explosive vapor formation in shock boiling mode. A method for calculating the cavitation in the regime of the fluctuation emergence of bubbles was approbated.


Peculiarities of the dynamic behavior of bubbles in a cluster caused by their hydrodynamic interaction

A.A. Gubaidullin and A.S. Gubkin
Tyumen Branch of the Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Tyumen, Russia
Tyumen State University, Tyumen, Russia
Keywords: bubble cluster, hydrodynamic interaction of bubbles, heat exchange of a bubble with liquid
Pages: 453462

Abstract >>
Numerical investigation of the collective interaction of bubbles in clusters of different configurations was carried out. The mathematical model was used, which accounted for the compressibility and viscosity of the liquid as well as the hydrodynamic interaction between the bubbles. The heat exchange of gas bubbles with liquid was handled within the framework of a two-temperature scheme. An expression for the heat flux to the bubble unit surface was used, which makes it possible to describe the heat exchange of gaseous bubbles with the liquid in a fairly wide range of the values of the liquid pressures and temperatures. The behavior of an individual bubble in the collective of bubbles at an instantaneous compression and at a periodic disturbance of different frequencies was investigated. It is shown that under certain conditions, considerable compression ratios and, as a consequence, high temperatures and temperatures are reached for some bubbles. The influence of the cluster configuration has been investigated. It is shown by the examples of a cluster of three embedded dodecahedra, linear and stochastic clusters that the configuration of the cluster may affect strongly its dynamics.


Buoyancy effects in steeply inclined air-water bubbly shear flow in a rectangular channel

K. Sanaullah1, M. Arshad2, A. Khan1, and I.R. Chughtai2

1Faculty of Engineering, UNIMAS, Kota Samarahan, Malaysia

2Department of Chemical Engineering, Nilore, Islamabad, Pakistan


Keywords: gas-liquid bubbly flow, void fraction, mean shear velocity
Pages: 463473
Abstract >>
We report measurements of two-dimensional (B/D = 5) fully turbulent and developed duct flows (overall length/depth, L/D = 60; D-based Reynolds number Re > 104) for inclinations to 30 from vertical at low voidages (< 5 % sectional average) representative of disperse regime using tap water bubbles (4-6 mm) and smaller bubbles (2 mm) stabilised in ionic solution. Pitot and static probe instrumentation, primitive but validated, provided adequate (10 % local value) discrimination of main aspects of the mean velocity and voidage profiles at representative streamwise station i.e L/D = 40. Our results can be divided into three categories of behaviour. For vertical flow (0) the evidence is inconclusive as to whether bubbles are preferentially trapped within the wall-layer as found in some, may be most earlier experimental works. Thus, the 4-mm bubbles showed indication of voidage retention but the 2-mm bubbles did not. For nearly vertical flow (5) there was pronounced profiling of voidage especially with 4-mm bubbles but the transverse transport was not suppressed sufficiently to induce any obvious layering. In this context, we also refer to similarities with previous work on one-phase vertical and nearly vertical mixed convection flows displaying buoyancy inhibited mean shear turbulence. However, with inclined flow (10+ degrees) a distinctively layered pattern was invariably manifested in which voidage confinement increased with increasing inclination. In this paper we address flow behavior at near vertical conditions. Eulerian, mixed and VOF models were used to compute voidage and mean velocity profiles.


Steam-water flow in geothermal wells

A.N. Shulyupin1 and A.A. Chermoshentseva2

1Mining Institute FEB RAS, Khabarovsk, Russia

2Kamchatka State Technical University, Petropavlovsk-Kamchatskii, Russia


Keywords: steam-water flow, well, feeding zone, hot-water reservoir, mathematical model, flow rate
Pages: 475480
Abstract >>
A mathematical model was developed for calculation of steam-water flow in a geothermal well for the feeding interval. The model assumes a variable mass flow rate over the channel length. The basis for this model are the flow continuity equation, momentum and energy conservation equations, taken with account for variable mass flow. The model was implemented as a computer code suitable for calculation of flow parameters upstream (downward the top level of the feeding zone). Then this model was applied for wells in the Mutnovskii geothermal field, this revealed a geyser-type mechanism of flow instabilities with the pressure oscillation period about ten minutes. The remedy for these oscillations was offered.


Experimental study of negative temperatures in lithium-bromide absorption refrigerating machines

K.I. Stepanov1, D.G. Mukhin1, S.V. Alekseenko1, and  O.V. Volkova2

1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

2Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics, Institute of Refrigeration and Biotechnology, St. Petersburg, Russia

Keywords: lithium-bromide absorption chiller, refrigerant, lithium bromide, coefficient of performance (COP), cold of low temperatures
Pages: 481489
Abstract >>
The authors have developed a method and presented experimental data for obtaining negative temperatures of evaporation in lithium-bromide absorption chillers driven by heat recovery. It has been found that the attainable temperature of the refrigerated medium is the value of -5 C.


Mathematical modelling of heat transfer process in layered materials accounting for phase transitions in individual layers

O.N. Lyubimova and K.N. Pestov

Far Eastern Federal University, Vladivostok, Russia

Keywords: phase transition of the first kind, thermal conductivity, melting, crystallization
Pages: 491499
Abstract >>
A mathematical model has been constructed for determining the temperature fields and motion of the phase transition boundaries without using the classical Stefan condition and the concentrated heat capacity. The model makes it possible to determine more accurately the location of the phase transition front and may be used at the computations for layered materials in the cases when there are several fronts, and they can merge. The modeling of the problem on determining the melting boundary in a three-layer material has been carried out for the one-dimensional case.



The density and thermal expansion of dysprosium in the temperature range 1101950 K

Yu.M. Kozlovskii  and  S.V. Stankus

Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia


Keywords: coefficient of thermal expansion, density, dysprosium, solid and liquid states, the Neel point
Pages: 501508
Abstract >>
The results of dilatometric studies of thermal coefficient of linear expansion of dysprosium in the temperature range 110-1950 K are presented. The measurements were performed with an accuracy of (1.5-2.0)10-7 K-1. The approximation dependences of thermal coefficient of linear expansion were obtained. The reference tables of dysprosium thermal properties for the range 110-1950 K of solid and liquid states were constructed using the previous results obtained by the gamma method. The character of thermal coefficient of linear expansion changes in the area of the Neel point has been established. Its critical exponents and the critical amplitudes have been determined. It is shown that both above and below the Neel temperature, the experimental data cannot be processed with a single scaling equation. A comparison with the published data has been performed.



Thermodynamic analysis of marble from Slyudyanka deposits 

V.S. Engelsht1 and V.Zh. Muratalieva2

1Institute of Physical and Technical Problems and Material Science NAS KR, Bishkek, Kyrgyzstan

2Kyrgyz State Technical University, Bishkek, Kyrgyzstan


Keywords: thermodynamic analysis, marble, monolith, heating, melting
Pages: 509514
Abstract >>
The authors have studied the change in the component composition of wollastonite marble from Slyudyanka deposits at increasing pressure (p = 0.1-12000 MPa) and temperature (T = 300-6000 K). Metamorphism of marble maturation has been found. The essence of maturation is the calcite melting, carbon dioxide deposition, the monolith compaction, the transformation of mineral composition at pressure increase up to the value of the initial components. When the pressure value reaches 12000 MPa the original components are reproduced, and the maturation of marble completes. Thermodynamic analysis reveals the secrets of the marble origin.


Capillary waves at microdroplet coalescence with a liquid layer

A.A. Fedorets1,2, I.V. Marchuk2,3, P.A. Strizhak4, and O.A. Kabov3,4

1Tyumen State University, Tyumen, Russia

2Novosibirsk State University, Novosibirsk, Russia

3Kutateladze Institute of Thermophysics  SB RAS, Novosibirsk, Russia

4Tomsk Polytechnic University, Tomsk, Russia

Keywords: capillary waves, microdroplets, coalescence, droplet cluster, evaporation, condensation, liquid layer, local heating
Pages: 515518
Abstract >>
The quickly damped capillary waves generated at coalescence of microdroplets (diameter of up to 100 m), formed in a gas atmosphere at water vapor condensation, with the horizontal layer of water are studied experimentally. Evaporation takes place at intensive local heating of liquid from the substrate side. To visualize and measure the deformations, the Schlieren technique and high-speed video (up to 54000 f/s) are applied. The measured wave amplitude varies within 1-6 m, and this is consistent with the magnitude of the surface energy of coalescing microdroplets. The waves are generated by the energy of droplet surface.


Effect of heater sizes on evaporation of a liquid film entrained by the gas flow in a microchannel with local heating

O.A. Kabov1, 2 and Yu.O. Kabova1

1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia

2Tomsk Polytechnic University, Tomsk, Russia

Keywords: evaporation, liquid film, local heating, microchannel, numerical studies
Pages: 519522
Abstract >>
The numerical study found the effect of changes in the longitudinal and transverse dimensions of the heater with keeping constant the area of heating on evaporation intensity, dynamics, and extreme thicknesses of a thin liquid film moving in a microchannel under the influence of the gas flow at local heating. It is shown that for relatively small heating, evaporation is more intense for the wide heaters than for the narrow ones. For the narrow and long heaters, evaporation process is slower, but then it is intensified in a short time.


80th Anniversary of Vladimir E. Nakoryakov

Editorial Board
Siberian Branch of the RAS, Novosibirsk, Russia
Pages: 523524

Abstract >>
26 July 2015 is the 80th anniversary of Vladimir E. Nakoryakov, the prominent Russian scientist in the field of thermophysics and heat power engineering and the full member of the Russian Academy of Sciences.