Zur Theorie der Thermodiffusion in Flüssigkeiten

Alexander, K.F.

doi:10.1515/zpch-1954-0115

Cited by 4 publications

(3 citation statements)

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“…Experiments have shown that the Soret coefficient features a temperature inversion, with the coefficient changing sign at a specific temperature [3,25]. The temperature inversion signals a substantial modification in the response of the solution to a thermal gradient.…”

Section: Introductionmentioning

confidence: 99%

A computational approach to calculate the heat of transport of aqueous solutions

Lecce

Albrecht

Bresme

2017

Sci Rep

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Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl− ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions.

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Section: Introductionmentioning

confidence: 99%

A computational approach to calculate the heat of transport of aqueous solutions

Lecce

Albrecht

Bresme

2017

Sci Rep

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“…19 Later studies reported positive Soret coefficients in a wide range of salt concentrations and salts, indicating that the concentration of salt increases in the cold region, and that the Soret coefficient is of the order of 10 −3 K −1 , i.e., about 2 orders of magnitude smaller than the values normally observed in colloidal and polymer aqueous suspensions. 20−24 Alexander 25 and later Gaeta et al 21 reported sign inversion in the Soret coefficient upon decreasing the average salt concentration of the solution. This work was performed with thermogravitational columns, where the concentration gradient is formed by a combination of a convective and thermal diffusion process.…”

Section: ■ Introductionmentioning

confidence: 99%

Alkali Halide Solutions under Thermal Gradients: Soret Coefficients and Heat Transfer Mechanisms

et al. 2013

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We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na(+)/K(+)-Cl(-)) to thermal gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret coefficient is of the order of 10(-3) K(-1) for a wide range of concentrations. These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T ∼ 315 K), whereas it increases at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight on the heat transport mechanism and the behavior of the Soret coefficient in aqueous solutions. The models employed in this work reproduce the magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish a correlation between the sign and magnitude of the Soret coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided.

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“…We have commented above that the heats of transport of KI, LiI and LiCl are negative at 25 ºC and 0.02 mol/L. Alexander[46],…”

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Thermal potential of ion-exchange membranes and its application to thermoelectric power generation

Jokinen

Manzanares

Kontturi

et al. 2016

Journal of Membrane Science

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Zur Theorie der Thermodiffusion in Flüssigkeiten

Cited by 4 publications

References 0 publications

A computational approach to calculate the heat of transport of aqueous solutions

A computational approach to calculate the heat of transport of aqueous solutions

Alkali Halide Solutions under Thermal Gradients: Soret Coefficients and Heat Transfer Mechanisms

Thermal potential of ion-exchange membranes and its application to thermoelectric power generation

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