On the interpretation of ternary diffusion measurements in low-molecular weight fluids by dynamic light scattering

Bardow, André

doi:10.1016/j.fluid.2006.11.006

Cited by 19 publications

(49 citation statements)

References 29 publications

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“…Initially, this is a complicated problem for which one has to consider coupling between velocity, density, temperature and two concentration fluctuations. To simplify the problem, as elucidated by other researchers in the field [4,37] and by us in previous publications [30,31], it is convenient to adopt a series of approximations, adequate for ternary liquid mixtures, before attempting any detailed calculation. Here, we shall consider the same approximations used in our previous publications [30,31], to which we refer for a detailed discussion.…”

Section: Fluctuating Hydrodynamicsmentioning

confidence: 99%

“…Finally we should mention Bardow [4] who combined previous works, considering both the statics and the dynamics of fluctuations in equilibrium ternary systems, while adopting some approximations adequate for mixtures in the liquid state, in particular the fact that concentration fluctuations in liquids relax much slower than temperature fluctuations. This approach is equivalent to the large Lewis number approximation, introduced by Velarde and Schechter [5], to simplify the calculation of the convection threshold in binary fluids.…”

Section: Introductionmentioning

confidence: 99%

“…This approach is equivalent to the large Lewis number approximation, introduced by Velarde and Schechter [5], to simplify the calculation of the convection threshold in binary fluids. All these works on equilibrium fluctuations in ternary mixtures [1][2][3][4] evaluated the correlation functions on the basis of the Mountain method of arbitrary initial conditions [6,7], an approach often adopted by books dealing with thermodynamic fluctuations [8][9][10]. There exists an alternative method, namely, fluctuating hydrodynamics (FHD) originally developed by Landau and Lifshitz [11] (with relevant subsequent contributions by Fox and Uhlenbeck [12]) for one-component fluid systems.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, detailed FHD predictions about finite size effects on non-equilibrium fluctuations [25][26][27] have been later experimentally verified, by Gradflex [28] in microgravity and by ground-based measurements [27,29] in the presence of buoyancy force. Hence, as a preliminary step in developing the theory of thermodynamic fluctuations in NE ternary mixtures, it was necessary to re-derive [30] the equilibrium results for ternary mixtures on the basis of FHD, for which the simplifications of Bardow [4] were adopted.…”

Section: Introductionmentioning

confidence: 99%

“…Next, in sect. 4, we obtain explicit expressions for the decay times of the NE composition fluctuations and analyze the related issue of the appearance of convection in sect. 4.2.…”

Section: Introductionmentioning

confidence: 99%

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Gravity effects on Soret-induced non-equilibrium fluctuations in ternary mixtures

Pancorbo¹,

Zárate²,

Bataller³

et al. 2017

Eur. Phys. J. E

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Abstract.We discuss the gravity effects on the dynamics of composition fluctuations in a ternary mixture around the non-equilibrium quiescent state induced by thermodiffusion when subjected to a stationary temperature gradient. We found that the autocorrelation matrix of concentration fluctuations can be expressed as the sum of two exponentially decaying concentration modes. Without accounting for confinement, we obtained exact analytical expressions for the two decay rates which, as a consequence of gravity, display a wave-number-dependent mixing. The stability of the quiescent solution is also examined, as a function of the two solutal Rayleigh numbers used to express the decay rates. After having discussed the dynamics of the two concentration modes, we calculate the corresponding amplitudes. Consequences for optical experiments are discussed.

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Section: Fluctuating Hydrodynamicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Next, in sect. 4, we obtain explicit expressions for the decay times of the NE composition fluctuations and analyze the related issue of the appearance of convection in sect. 4.2.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Gravity effects on Soret-induced non-equilibrium fluctuations in ternary mixtures

Pancorbo¹,

Zárate²,

Bataller³

et al. 2017

Eur. Phys. J. E

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Thermophysical Properties of a Refrigerant Mixture of R365mfc (1,1,1,3,3-Pentafluorobutane) and Galden® HT 55 (Perfluoropolyether)

Fröba

Kremer²,

Leipertz

et al. 2007

Int J Thermophys

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This work presents a comprehensive experimental study of various thermophysical properties of an azeotropic refrigerant mixture of 65 mass% R365mfc (1,1,1,3,3-pentafluorobutane) and 35 mass% Galden HT 55 (perfluoropolyether). Light scattering from bulk fluids has been applied for measuring both the thermal diffusivity and the speed of sound in the liquid and vapor phases under saturation conditions, between 293 K and the liquid-vapor critical point at 450.7 K. Furthermore, the speed of sound has been measured for the superheated-vapor phase along nine isotherms, between 393 and 523 K and up to a maximum pressure of about 2.5 MPa. For temperatures between 253 and 413 K, light scattering by surface waves on a horizontal liquid-vapor interface has been used for simultaneous determination of the surface tension and kinematic viscosity of the liquid phase. With light scattering techniques, uncertainties of less than ±2.0%, ±0.5%, ±1.5%, and ±1.5% have been achieved for the thermal diffusivity, sound speed, kinematic viscosity, and surface tension, respectively. In addition to vapor-pressure measurements between 304 and 448 K, the density was measured between 273 and 443 K using a vibrating-tube method. Here, measurements have been performed in the compressed-and saturated-liquid phases with uncertainties of ±0.3% and ±0.1%, respectively, as well as for the superheated vapor up to a maximum pressure of about 3 MPa with an uncertainty between ±0.3% and ±3%. Critical-point parameters were derived by combining the data obtained by different techniques. 449 0195-928X/07/0400-0449/0 © 2007 Springer Science+Business Media, LLC 450 Fröba, Kremer, Leipertz, Flohr, and Meurer

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Dynamic Light Scattering for the Measurement of Transport Properties of Fluids

Koller,

Rausch,

Fröba

2024

Int J Thermophys

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The present article summarizes experimental and theoretical considerations required for a proper use of dynamic light scattering (DLS) for the measurement of transport properties of fluids. It addresses not only recent advancements of the method, but also aims to provide recommendations to researchers who intend to apply the technique in the future. As outlined in this study, DLS is based on the analysis of scattered light governed by microscopic statistical or periodic fluctuations that originate from the thermal movement of molecules and/or particles at macroscopic thermodynamic equilibrium. The dynamics of these hydrodynamic fluctuations in the bulk of fluids or at their phase boundaries are related to the underlying diffusive processes and, thus, to the associated transport properties, and are reflected by the time-dependent correlation function of the scattered light intensity. The fundamentals of this type of detection, known as photon correlation spectroscopy (PCS), will be discussed in the present contribution in some more detail. It is emphasized that the experiments need to be designed carefully in accordance with theory in order to assign the measurement signals to the corresponding hydrodynamic fluctuations. If the necessary conditions are fulfilled, DLS allows the accurate determination of several transport properties including kinematic and dynamic viscosity, thermal diffusivity, mutual diffusivity, and sound attenuation, which may be accessed together with other thermophysical properties such as speed of sound and surface or interfacial tension. In some instances, also the simultaneous determination of several transport properties is possible. With the exception of the sound attenuation, expanded uncertainties for the mentioned transport properties down to 1 % can be achieved for various types of fluid systems over a wide range of thermodynamic states up to elevated temperatures and pressures as well as in the vicinity of critical points. This performance and versatility of the DLS technique is documented in the present study by highlighting measurement examples from recent thermophysical property research on different classes of working fluids relevant for process and energy technology.

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On the interpretation of ternary diffusion measurements in low-molecular weight fluids by dynamic light scattering

Cited by 19 publications

References 29 publications

Gravity effects on Soret-induced non-equilibrium fluctuations in ternary mixtures

Gravity effects on Soret-induced non-equilibrium fluctuations in ternary mixtures

Thermophysical Properties of a Refrigerant Mixture of R365mfc (1,1,1,3,3-Pentafluorobutane) and Galden® HT 55 (Perfluoropolyether)

Dynamic Light Scattering for the Measurement of Transport Properties of Fluids

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