Binary-mixture convection in connected channels heated from below

Glukhov, A. F.; Demin, V. A.; Putin, G. F.

doi:10.1134/s0015462807020020

Cited by 6 publications

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“…It is assumed that for ferroparticles the diffusion within the kerosene matrix is negligible as compared with the effect of kerosene component redistribution owing to thermodiffusion. Previously, we showed theoretically and experimentally that in long connected channels the thermal convection of binary molecular fluids substantially depends on the thermodiffusion characteristics of the mixture [2][3][4]. For the solutions of Na 2 SO 4 in water and of carbon tetrachloride in decane the period amounts from 10 min to half-hour but for the magnetic fluids the swing oscillation period reaches several hours (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…In some experiments, in which the magnetic fluid was maintained in equilibrium for several weeks, we managed to excite convective flow by only introducing artificial perturbations, for example, inclining the channels. The fluid flow along the vertical high-thermal-conductivity channel walls leads to the diffusion mixture separation in the horizontal cross-section [3]. Since the channel thickness is small as compared with the hight (h/d ∼ 30), the characteristic time of the thermal diffusion separation owing to horizontal temperature gradients is three orders smaller than the vertical mixture separation time.…”

Section: Methodsmentioning

confidence: 99%

“…In the medias of both types, near the equilibrium stability threshold, periodic changes in the channel flow direction were observed. The nature of the convective oscillations of molecular binary mixtures was established, the theory of the phenomenon was developed, numerical and analytical calculations were carried out, and the results were described in a series of papers [2][3][4]. It was revealed that in these oscillations the determining role is played by the positive thermodiffusion of a heavy molecular admixture.…”

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confidence: 99%

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Thermal magnetic nanosuspension convection in narrow channels

Glukhov¹,

Demin²,

Popov³

2013

Fluid Dyn

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The results of comparative experiments on the convection of magnetic fluids and molecular binary fluid mixtures in connected vertical channels heated from below are discussed. In both media, near the equilibrium stability threshold, flows in the form of specific swing oscillations are observed. The results of the experiment form a basis for a three-component model for magnetic fluid convection which takes into account the thermodiffusion separation of the dispersion medium components and the weak sedimentation of magnetic particles. The results of numerical simulation and experiment are compared.The specific low-frequency convective ferrofluid oscillations in connected vertical channels, described in [1], surprisingly turned out to be qualitatively similar to the binary mixture oscillations. In the medias of both types, near the equilibrium stability threshold, periodic changes in the channel flow direction were observed. The nature of the convective oscillations of molecular binary mixtures was established, the theory of the phenomenon was developed, numerical and analytical calculations were carried out, and the results were described in a series of papers [2][3][4]. It was revealed that in these oscillations the determining role is played by the positive thermodiffusion of a heavy molecular admixture.In order to understand the nature of the convective oscillations in ferrofluids, novel comparative experiments were carried out with ferrofluids and aqueous sodium sulfate solutions. The experimental results obtained make a basis for formulating equations that describe the convection of the magnetic fluid as a three-component fluid consisting of a binary carrier filled with magnetic particles.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Thermal magnetic nanosuspension convection in narrow channels

Glukhov¹,

Demin²,

Popov³

2013

Fluid Dyn

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“…The measuring devices were connected to the USB port of the computer through a RS232/RS485 converter and were inquired using the Termodat 7.29 code. The temperature measurement technique used in the experiment is described in detail in [7]. As the measure of the flow intensity we used the dimensionless quantity Θ = |ζ|/ΔT , where ζ is the thermocouple reading (see Fig.…”

Section: Experimentmentioning

confidence: 99%

“…The concentration inhomogeneities are generated by thermal diffusion due to horizontal temperature gradients, which, in turn, occur only in convective circulation of the mixture. The nature of these oscillations is discussed in [7] and confirmed by numerical modeling using the finite difference method.…”

Section: Experimentmentioning

confidence: 99%

Separation of mixtures in connected channels

Glukhov

Demin

Putin

2009

J Appl Mech Tech Phy

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The stationary modes of thermal convection of a binary mixture in connected channels of finite height were studied experimentally and theoretically. The effects of positive and negative thermal diffusion on the convection were examined. The ranges of parameters corresponding to the modes of soft and rigid initiation of convection were determined. Vertical distributions of the temperature and concentration fields were found for various values of the thermal diffusion parameter.Key words: binary fluid, connected channels, positive and negative thermal diffusion effects, separation of mixture into components. Introduction.As is known, thermoconcentration convection occurs in a nonuniformly heated fluid mixture of complex composition in a gravity filed. In this case, density inhomogeneity arises from a competition of two convection mechanisms. The first mechanism has a thermogravitation nature and is due to the temperature dependence of the fluid density, and the second mechanism is due to the inhomogeneous concentration distribution of the heavy or light component in the mixture. The existence of two competing lifting forces leads to more complex behavior of the system than in the case of a homogeneous fluid. The forces are determined by the temperature and concentration coefficients of the density and by the temperature and concentration gradients. In most mixtures, the presence of temperature gradients is responsible for the occurrence of concentration gradients. (This phenomenon is called thermal diffusion.) In this case, free convective flow is influenced by the concentration inhomogeneity due to thermal diffusion.A horizontal layer of a binary mixture heated from below undergoes thermal diffusion separation along the vertical, which, in the case of a positive Soret effect with equilibrium instability promotes the development of monotonic perturbations [1]. In the case of anomalous thermal diffusion, where thermogravitation and anomalous thermal diffusion mechanisms of convection initiation counteract with each other, oscillatory mechanisms of development of equilibrium instability dominate.The purpose of the present work was to study stationary and oscillatory convective flows of a binary mixture in connected channels of finite height taking into account positive and negative thermal diffusion. Convection of one-component fluids and binary mixtures in connected channels has been studied previously [2,3]. In this case, thermal diffusion was ignored, and the source of concentration inhomogeneities was a linear vertical concentration profile of the heavy component on the boundaries of the channels.1. Formulation of the Problem. We consider two vertical channels of finite height with ideal heatconducting boundaries (Fig. 1). The channels have square section and are connected at the top and bottom by short bridges of the same profile. In the theoretical study, the influence of the bridges is ignored. The calculations are performed for the same set of geometrical parameters as in the experiment. Estimates show that, ...

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Average stationary binary-mixture convection in connected channels in the presence of high-frequency vibration

Glukhov¹,

Demin²

2009

Fluid Dyn

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Binary-mixture convection in connected channels heated from below

Cited by 6 publications

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Thermal magnetic nanosuspension convection in narrow channels

Thermal magnetic nanosuspension convection in narrow channels

Separation of mixtures in connected channels

Average stationary binary-mixture convection in connected channels in the presence of high-frequency vibration

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