scholarly journals Experimental Investigation of Thermal Diffusion in Binary and Ternary Hydrocarbon Mixtures

2021 ◽  
Author(s):  
Seyyed Arash Mousavi
Keyword(s):  
Thermal Diffusion ◽  
Soret Effect ◽  
Measurement Instrument ◽  
Optical Interferometry ◽  
Temperature Fields ◽  
Soret Coefficient ◽  
Hydrocarbon Mixtures ◽  
Space Experiments ◽  
Convective Motions ◽  
Laser Sources

In a multi-component liquid mixture, the process of disassociation of the components induced by thermal gradient is called thermal diffusion or Soret effect. This effect plays a crucial role in separation of the components in hydrocarbon mixtures of oil. Accordingly, the main goal of this study is to experimentally investigate the Soret effect in binary and ternary hydrocarbon mixtures. Optical interferometry technique with Mach-Zehnder scheme was used to conduct the experiments. The interferometry techniques are not intrusive and the separation of the components in the mixture is not affected by the measurement instrument. A Soret cell is defined as a cubic cavity where the sample mixture is placed in it and, the separation of the components takes place in the cell by heating it from the above. Soret cells are used in convectionless experiments and natural convections are undesirable. The Soret cell used in space experiments was re-designed and optimized for ground-based experiments to avoid the natural convections. Computational studies were made on the both cells to obtain the temperature and velocity fields. Then a set of thermal diffusion experiments conducted in order to compare the performance of the cells. The results shows that the induced convective motions in the second cell are significantly weaker than those in the previous cell which is desirable. In the next step, the effect of the inclination of the cell on the thermal diffusion was studied. First numerical analysis was made to find the velocity and temperature fields in different inclinations and then a set of experiments was performed and the concentration distribution of the components in a binary mixture in different inclinations of the cell was found. Finally, ground based experiments were performed to study the thermal diffusion in five ternary hydrocarbon mixtures. Optical interferometry with Mach-Zehnder scheme using two laser sources with different wavelengths was used. The Soret information of one of the mixtures is available in the literature and this mixture was studied here to validate the present experimental setup. The temperature and concentration of the mixtures were measured successfully in the Soret cell and a table of the measured Soret coefficient were provided.

scholarly journals Experimental Investigation of Thermal Diffusion in Binary and Ternary Hydrocarbon Mixtures

2021 ◽  
Author(s):  
Seyyed Arash Mousavi
Keyword(s):  
Thermal Diffusion ◽  
Soret Effect ◽  
Measurement Instrument ◽  
Optical Interferometry ◽  
Temperature Fields ◽  
Soret Coefficient ◽  
Hydrocarbon Mixtures ◽  
Space Experiments ◽  
Convective Motions ◽  
Laser Sources

In a multi-component liquid mixture, the process of disassociation of the components induced by thermal gradient is called thermal diffusion or Soret effect. This effect plays a crucial role in separation of the components in hydrocarbon mixtures of oil. Accordingly, the main goal of this study is to experimentally investigate the Soret effect in binary and ternary hydrocarbon mixtures. Optical interferometry technique with Mach-Zehnder scheme was used to conduct the experiments. The interferometry techniques are not intrusive and the separation of the components in the mixture is not affected by the measurement instrument. A Soret cell is defined as a cubic cavity where the sample mixture is placed in it and, the separation of the components takes place in the cell by heating it from the above. Soret cells are used in convectionless experiments and natural convections are undesirable. The Soret cell used in space experiments was re-designed and optimized for ground-based experiments to avoid the natural convections. Computational studies were made on the both cells to obtain the temperature and velocity fields. Then a set of thermal diffusion experiments conducted in order to compare the performance of the cells. The results shows that the induced convective motions in the second cell are significantly weaker than those in the previous cell which is desirable. In the next step, the effect of the inclination of the cell on the thermal diffusion was studied. First numerical analysis was made to find the velocity and temperature fields in different inclinations and then a set of experiments was performed and the concentration distribution of the components in a binary mixture in different inclinations of the cell was found. Finally, ground based experiments were performed to study the thermal diffusion in five ternary hydrocarbon mixtures. Optical interferometry with Mach-Zehnder scheme using two laser sources with different wavelengths was used. The Soret information of one of the mixtures is available in the literature and this mixture was studied here to validate the present experimental setup. The temperature and concentration of the mixtures were measured successfully in the Soret cell and a table of the measured Soret coefficient were provided.

Numerical Analysis of Thermal-Solutal Convection in Heterogeneous Porous Media

2005 ◽  
Vol 73 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Charles-Guobing Jiang ◽  
M. Ziad Saghir ◽  
M. Kawaji
Keyword(s):  
Porous Media ◽  
Thermal Diffusion ◽  
Soret Effect ◽  
Heterogeneous Porous Media ◽  
Soret Coefficient ◽  
Solutal Convection ◽  
Coefficient Distribution ◽  
Separation Ratio ◽  
Diffusion In Porous Media ◽  
Vertical Cavity

Thermal diffusion, or Soret effect, in porous media is mathematically modeled with the Firoozabadi model based on non-equilibrium thermodynamics. The Soret effect in a binary mixture is investigated in a vertical cavity with heterogeneous permeability, where natural convection can occur. The thermo solutal convection with heterogeneous permeability was studied in terms of flow pattern, concentration distribution, component separation ratio, and Soret coefficient distribution. A consistent analysis was conducted and it is concluded that the Soret coefficient of thermal diffusion in porous media strongly depends on the heterogeneity of permeability.

A Model of Flow in a Closed-Loop Thermosyphon Including the Soret Effect

1985 ◽  
Vol 107 (4) ◽  
pp. 840-849 ◽  
Author(s):  
J. E. Hart
Keyword(s):  
Rayleigh Number ◽  
Soret Effect ◽  
Vertical Plane ◽  
Soret Coefficient ◽  
Chaotic Motions ◽  
Thermohaline Convection ◽  
Existence And Stability ◽  
Convective Motions ◽  
Steady Solutions ◽  
Set Up

This theoretical study addresses the nature of convective motions in a toroidal loop of binary fluid oriented in the vertical plane and heated from below. The boundaries of the loop are impermeable, but gradients of the solute can be set up by Soret diffusion in the direction around the loop. The existence and stability of steady solutions are discussed over the Rayleigh number-Soret coefficient parameter plane. When the Soret coefficient is negative, periodic and chaotic oscillations analogous to those of thermohaline convection are predicted. When the Soret coefficient is positive, relaxation oscillations and low Rayleigh number chaotic motions are found. Both sets of phenomena are predicted to occur for realistic thermosyphon parameters.

Mass transfer dominated by thermal diffusion in laminar boundary layers

1997 ◽  
Vol 336 ◽  
pp. 379-409 ◽  
Author(s):  
PEDRO L. GARCÍA-YBARRA ◽  
JOSE L. CASTILLO
Keyword(s):  
Mass Transport ◽  
Boundary Layers ◽  
Thermal Diffusion ◽  
Mass Fraction ◽  
Soret Effect ◽  
Second Order ◽  
Brownian Diffusion ◽  
Diffusion Transport ◽  
Laminar Boundary Layers ◽  
Fraction Distribution

The concentration distribution of massive dilute species (e.g. aerosols, heavy vapours, etc.) carried in a gas stream in non-isothermal boundary layers is studied in the large-Schmidt-number limit, Sc[Gt ]1, including the cross-mass-transport by thermal diffusion (Ludwig–Soret effect). In self-similar laminar boundary layers, the mass fraction distribution of the dilute species is governed by a second-order ordinary differential equation whose solution becomes a singular perturbation problem when Sc[Gt ]1. Depending on the sign of the temperature gradient, the solutions exhibit different qualitative behaviour. First, when the thermal diffusion transport is directed toward the wall, the boundary layer can be divided into two separated regions: an outer region characterized by the cooperation of advection and thermal diffusion and an inner region in the vicinity of the wall, where Brownian diffusion accommodates the mass fraction to the value required by the boundary condition at the wall. Secondly, when the thermal diffusion transport is directed away from the wall, thus competing with the advective transport, both effects balance each other at some intermediate value of the similarity variable and a thin intermediate diffusive layer separating two outer regions should be considered around this location. The character of the outer solutions changes sharply across this thin layer, which corresponds to a second-order regular turning point of the differential mass transport equation. In the outer zone from the inner layer down to the wall, exponentially small terms must be considered to account for the diffusive leakage of the massive species. In the inner zone, the equation is solved in terms of the Whittaker function and the whole mass fraction distribution is determined by matching with the outer solutions. The distinguished limit of Brownian diffusion with a weak thermal diffusion is also analysed and shown to match the two cases mentioned above.

Non-Equilibrium Molecular Dynamics Study of the Influence of Branching on the Soret Coefficient of Binary Mixtures of Heptane Isomers

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xiaoyu Chen ◽  
Ruquan Liang ◽  
Lichun Wu ◽  
Gan Cui
Keyword(s):  
Molecular Dynamics ◽  
Thermal Diffusion ◽  
Soret Coefficient ◽  
Isomer Mixture ◽  
Acentric Factor ◽  
Diffusion Behavior ◽  
The Difference ◽  
Non Equilibrium Molecular Dynamics ◽  
Molecular Branching ◽  
Non Equilibrium

Abstract Equimolar mixtures composed of isomers were firstly used to investigate the molecular branching effect on thermal diffusion behavior, which was not disturbed by factors of molecular mass and composition in this work. Eight heptane isomers, including n-heptane, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane and 3-ethylpentane, were chosen as the researched mixtures. A non-equilibrium molecular dynamics (NEMD) simulation with enhanced heat exchange (eHEX) algorithm was applied to calculate the Soret coefficient at T = 303.15 T=303.15  K and P = 1.0 atm P=1.0\hspace{0.1667em}\text{atm} . An empirical correlation based on an acentric factor was proposed and its calculation coincides with the simulated results, which showed the validity of the NEMD simulation. It is demonstrated that the isomer with higher acentric factor has a stronger thermophilic property and tends to migrate to the hot region in the heptane isomer mixture, and the extent of thermal diffusion is proportional to the difference between the acentric factors of the isomers.

scholarly journals Thermophoresis: The Case of Streptavidin and Biotin

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 376 ◽  
Author(s):  
Doreen Niether ◽  
Mona Sarter ◽  
Bernd W. Koenig ◽  
Jörg Fitter ◽  
Andreas M. Stadler ◽  
...  
Keyword(s):  
Heavy Water ◽  
Rayleigh Scattering ◽  
Soret Effect ◽  
Binding Constants ◽  
Soret Coefficient ◽  
Protein Solutions ◽  
Elastic Neutron ◽  
Solvent Interactions ◽  
Free Protein ◽  
Promising Tool

Thermophoretic behavior of a free protein changes upon ligand binding and gives access to information on the binding constants. The Soret effect has also been proven to be a promising tool to gain information on the hydration layer, as the temperature dependence of the thermodiffusion behavior is sensitive to solute–solvent interactions. In this work, we perform systematic thermophoretic measurements of the protein streptavidin (STV) and of the complex STV with biotin (B) using thermal diffusion forced Rayleigh scattering (TDFRS). Our experiments show that the temperature sensitivity of the Soret coefficient is reduced for the complex compared to the free protein. We discuss our data in comparison with recent quasi-elastic neutron scattering (QENS) measurements. As the QENS measurement has been performed in heavy water, we perform additional measurements in water/heavy water mixtures. Finally, we also elucidate the challenges arising from the quantiative thermophoretic study of complex multicomponent systems such as protein solutions.

Simulations of Flow and Temperature Fields in a Two Heater PCR Device

Volume 4 ◽  
2004 ◽  
Author(s):  
Tom Mautner
Keyword(s):  
Thermal Diffusion ◽  
Wall Temperature ◽  
Lattice Boltzmann ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Thermal Coupling ◽  
Uniform Temperature ◽  
Temperature Distributions ◽  
Flow Through ◽  
Heater Design

One module in a bioagent detector currently under development involves a new two-heater, flow-through polymerase chain reaction (PCR) module which is being designed to save space and power and to reduce the amplification time. As in all PCR devices, thermal cycling requires three temperatures and residence times. These are 90–95°C for DNA denaturation, 50–65°C for hybridization and 72–77°C for replication with a time ratio of 4:9:4. The current design uses two heaters with heat conduction in the substrate providing the hybridization temperature. Typically, the flow and temperature fields in microfluidic devices have three-dimensional complexity, thus numerical simulations were performed to provide design guidelines in the development of the two-heater PCR device. The lattice Boltzmann (LB) method was used to perform low Reynolds number (typically Re = 0.10) simulations for two and three dimensional channel geometries having various wall temperature distributions. The momentum and thermal lattice Boltzmann equations were coupled via a body force term in the momentum equation. Initial computations using two- and three-heater configurations in two dimensions demonstrated excellent comparisons with published data provided that both the top and bottom walls were heated. If only one wall was heated, large vertical thermal gradients occurred resulting in non-uniform temperature fields. However, when the same conditions were applied to three dimensional channels, lower temperatures were observed in the center of the channel regardless of the wall temperatures or channel aspect ratio. Parametric studies were performed to evaluate the effects of thermal coupling, thermal diffusion coefficients, entrance temperatures, wall temperature configurations and channel geometry. If was found that moderate variation of the thermal diffusion coefficient produced only minor differences in the temperature field, and large changes in the thermal coupling magnitude demonstrated transition from natural to forced convection flows. The simulations also indicate that the largest effect on flow and temperature uniformity arises from the applied wall temperature distribution (various thickness channel walls). It was found, in 2D, that if the channel wall starts from ambient temperature, the applied heating, on the outer surfaces only, may not result in the desired wall or fluid temperatures. However, once the channel walls are heated to a uniform temperature, excellent temperature distributions are obtained for both thick and thin channel walls. These results indicate that the two-heater design has potential in providing a new flow-through PCR device. However, careful attention must be paid to the wall heater design to provide the required sample temperatures.

The Soret Effect: A Review of Recent Experimental Results

2005 ◽  
Vol 73 (1) ◽  
pp. 5-15 ◽  
Author(s):  
Jean K. Platten
Keyword(s):  
Rayleigh Scattering ◽  
Soret Effect ◽  
Organic Liquid ◽  
Oil Industry ◽  
Liquid Mixtures ◽  
Beam Deflection ◽  
Soret Coefficient ◽  
Onset Of Convection ◽  
New Techniques ◽  
Scattering Technique

In the first part of the paper, we recall what the Soret effect is, together with its applications in science and industry. We emphasize the need to have a reliable data base for the Soret coefficient. Next we review the different techniques to measure the Soret coefficient (elementary Soret cell, beam deflection technique, thermal diffusion forced Rayleigh scattering technique, convective coupling and, in particular, the onset of convection in horizontal layers and the thermogravitational method). Results are provided for several systems, with both negative and positive Soret coefficients, and comparison between several laboratories are made for the same systems. We end with “benchmark” values of the Soret coefficient for some organic liquid mixtures of interest in the oil industry and to which all future new techniques should refer before gaining confidence. We conclude that correct values of the Soret coefficient can be obtained in earth conditions and we deny the need to go to microgravity.

Thermal Diffusion in Hydrogen‐Hydrocarbon Mixtures

1949 ◽  
Vol 17 (4) ◽  
pp. 408-410 ◽  
Author(s):  
H. G. Drickamer ◽  
S. L. Downey ◽  
N. C. Pierce
Keyword(s):  
Thermal Diffusion ◽  
Hydrocarbon Mixtures
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