Measurement Of Soret Coefficients Research Articles

Accurate measurement of Soret coefficients in binary hydrocarbons mixtures based on composite methods

The Soret effect is a significant factor in various scenarios, with thermodiffusion in binary systems serving as a common method for the study. Most research focuses rarely on the distribution characteristics of components in diffusion systems; and Soret coefficients in the porous media could not be obtained by typical methods based on the thermodiffusion column, which are particularly important in the field of oil and gas development. Moreover, experiments on ground conditions have struggled to determine the Soret coefficient accurately due to the convective effect caused by gravity differentiation. The thermodiffusion behavior of n-pentane (C5) and n-heptane (C7) binary mixtures in both bulk and porous media conditions have been investigated, aiming to provide corrected coefficients that mitigate the influence of gravity using theoretical derivation. A new method was proposed to calculate the Soret coefficients in this work by establishing a model based on gas chromatography technology. Dynamic variation of component concentration along the path was studied, and the corresponding Soret coefficients were calculated and analyzed in parallel. The results indicate that the concentration and temperature exhibit a logarithmic relationship with the distance from the heat source. The Soret coefficient values obtained from measurements in porous media are closer to the theoretically corrected values, which do not account for gravity effects. Additionally, as the permeability decreases, the counteracting effect of porous media on convection becomes more pronounced. Therefore, it presents a novel method for accurately measuring the Soret coefficient that ignores convection to some extent.

The Influence of Bounding Plates on Species Separation in a Vertical Thermogravitational Column

In this paper, an analytical and numerical analysis of the species separation in a binary mixture is performed. The main objective is to study the influence of the thickness and the nature of the bounding plates of the thermogravitational column (TGC) on species separation. The theory of Furry, Jones and Onsager is extended to the cases where bounding conducting walls enclose the TGC. The governing 2-dimensional equations are solved numerically using COMSOL Multiphysics software. A good agreement is found between the analytical and the numerical results. It is shown that the determination of the thermal diffusion coefficient, DT, from the measurement of the vertical mass fraction gradient of binary solutions, does not depend on the temperature difference imposed on the vertical column either on the outer walls of the cavity or on the inner walls in contact with the binary solutions. However, it is found that this result is no longer valid in the case of a binary gas. To our knowledge, in all earlier studies, dealing with the measurement of Soret coefficients in binary fluids, the nature and the thickness of the bounding walls were not considered.

Results of the DCMIX1 experiment on measurement of Soret coefficients in ternary mixtures of hydrocarbons under microgravity conditions on the ISS.

The Soret coefficients of a set of ternary systems of 1,2,3,4-tetrahydronaphthalene (THN), isobutylbenzene (IBB), and n-dodecane (nC12) at 298.15 K were measured under microgravity condition aboard the International Space Station in the frame of the DCMIX1 experiment. The present work includes a comprehensive study of possible data processing sequences for the interpretation of interferometric Soret experiments in ternary systems. Several data processing methodologies are discussed. A significant concentration dependence of the Soret coefficients is observed. In the present study, we have obtained large and positive values for THN and negative ones for IBB in all investigated systems. A linear relation between the Soret coefficients of two components is derived for each system and allows validating experimentally the coefficients measured in other experiments.

Measurement of Soret coefficients in a ternary mixture of toluene-methanol-cyclohexane in convection-free environment.

We report on the measurement of Soret (ST) coefficients in the ternary system toluene (T)-methanol (M)-cyclohexane (Ch) onboard the International Space Station in the experiment selectable optical diagnostic instrument/DCMIX2 (Diffusion Coefficients Measurement in ternary mIXtures). Nine experiments were conducted in the range of mean temperatures between 298.15 K and 306.15 K in the mixture with composition 0.62 (T)-0.31 (M)-0.07 (Ch) in mass fractions. A linear dependence of the Soret coefficients on temperature was established for the ternary mixture. It has also been found that, over considered range of mean temperatures, the Soret coefficients of toluene are small and positive, while the Soret coefficients for methanol are negative and, at least, two times larger. The present work also presents a comprehensive study of possible methodologies to process raw data from the Soret experiment in ternary mixtures. All the experiments were processed by seven different schemes and two of them were identified as the most reliable. We also investigate the error propagation and explain the reasons for the discrepancy of the results obtained by different schemes.

Science Research of Microgravity Satellite SJ-10

The program SJ-10, one of the scientific satellite programs in the Strategic Priority Research Program on Space Science, the Chinese Academy of Sciences, was launched on April 6, 2016. There are totally 19 scientific payloads, a multi-function furnace for 8 material researches and three-dimensional cell cultures for the neural stem cell and the hematopoietic stem cell respectively. The recoverable satellite consists mainly of two capsules:a recoverable capsule was recovered on 18 April 2016, with all payloads of life science, the multi-function furnace and the payload for measurement of Soret Coefficients of Crude Oil (SCCO); and an un-recoverable capsule continued to work in additional 3 days with all other physics payloads. The experiments were operated <i>via</i> teleoperations, and all experimental data were received by the ground station in real time. The data and recoverable samples are analyzed by the experiment teams of the program.

レーザホログラフィーによる熱拡散の可視化とSoret係数の計測

本研究では矩形容器内の溶液に密度的に安定な鉛直温度差を与えた場合に生じる熱拡散現象，Soret効果に注目し，レーザホログラフィー実時間干渉法を適用して行う独自のSoret係数計測システムを提案する．本システム，本実験方法により，Soret効果により生じる濃度分布を干渉縞で捉えることが可能であった．また，干渉縞が等屈折率線と一致し，溶液の屈折率が温度と濃度の関数であることを利用することで，干渉縞から系内濃度が計測でき，またSoret効果の厳密解を通じてSoret係数が算出できた．Soret係数の実験値と文献値とを比較したところ，両者の一致は良好であり，本システムは十分実用的であることがわかった．

Measurement of the Soret and diffusion coefficients for benchmark binary mixtures by means of digital interferometry

We report on the development of the optical digital interferometry (ODI) technique for measuring diffusion and Soret coefficients. The unique feature of this method is that it traces the transient path of the system in the entire two-dimensional cross section of a cell. In this way, it is applicable not only for measurements of Soret coefficients, but also for studying diffusive transport mechanism and convection. Presently, this method is not widely used and, in our view, not because of fundamental limitations but rather due to a lack of properly developed postexperimental procedures of the raw data analysis. Thus, in this paper our attention is focused on the successive analysis of different steps: the fringe analysis, the choice of reference images, the thermal design of the cell, and multiparameter fitting procedure. Using the ODI technique, we have measured the diffusion and the Soret coefficients for three binary mixtures composed of dodecane (C(12)H(26)), isobutylbenzene, and 1,2,3,4-tetrahydronaphtalene at a mean temperature of 25(∘)C and 50 wt. % in each component. These measurements were compared with their benchmark values and show an agreement within less than 3%.

Open Questions on Reliable Measurements of Soret Coefficients

This study was motivated by experimental problems arising in the design of optical digital interferometry for measurements of Soret coefficients in laboratory conditions. Our attention is mainly focused on thermal design of the set-up. The goal is to establish a linear temperature profile inside the experimental cell while heating from above. The measures for preventing deleterious convection inside the working liquid and outside the experimental cell (in the surrounding gas) are carefully examined. It is pointed out that both convection in the liquid and in the surrounding gas have a strong negative effect on the quality of optical measurements.

Transient-state method for coupled evaluation of Soret and Fick coefficients, and related tortuosity factors, using free and porous packed thermodiffusion cells: Application to CuSO4 aqueous solution ( 0.25M)

The measurement of Soret coefficients in liquids is not easy and usually not very precise because the resulting concentration gradient is small and moreover can be perturbed by undesired convection currents. In order to suppress, or to drastically reduce these convection currents, the use of a porous medium is sometimes suggested. The question arises as to whether the Soret coefficient is the same in free fluid and in porous medium. This is the aim of this paper. To this end, for a given liquid mixture, the time evolution of the vertical concentration gradient is experimentally measured in the same thermodiffusion cell filled first with the free liquid and next with a porous medium followed by saturation by the liquid mixture. Both the isothermal diffusion (Fick) coefficient and the Soret coefficient can be deduced, providing that a correct working equation is used. The proposed equation results from integration of the general mass conservation equation with realistic boundary conditions (zero mass flux at the boundaries) and some simplifying assumptions rendering this equation more tractable than the one proposed some decades ago by Bierlein (J.A. Bierlein, J. Chem. Phys. 23, 10 (1955)). The method is applied here to an electrolytic solution (CuSO4, 0.25 M) at a mean temperature of 37 degrees C. The Soret coefficients in free and porous medium (zircon microspheres in the range of 250-315 x 10(-6) m) may be considered to be equal ( S(T) = 13.2+/-0.5 x 10(-3) K(-1)) and the tortuosity factors for the packed medium are the same relative to thermodiffusion and Fick coefficients (tau = 1.51+/-0.02).

Reference Soret coefficients of natural isotopes and diluted alloys of tin

Measurements of Soret coefficients of tin alloys have been performed in the MFA-067 experiment of the automatic retrievable satellite EURECA. They complete the set of measurements performed in tin dilute alloys in microgravity manned laboratories. They allow also for an accurate determination of the isotopic thermomigration and for a better evaluation of the accuracy of microgravity measurements of the thermodiffusion factors. These data are compared to nonequilibrium condensed matter theories. A reasonable agreement has been obtained with the revised Enskog theory, and no electronic contribution could be identified.

1210. A modified type of thermal-diffusion cell, and its application to the measurement of Soret coefficients for solutions of carbon tetrachloride in benzene

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