Advances in Thermodiffusion and Thermophoresis (Soret Effect) in Liquid Mixtures

Abstract

Recent advances in thermodiffusion (Soret effect) in binary and higher multicomponent liquid mixtures are reviewed. The mixtures studied include the hydrocarbon, associating, molten metal and semiconductor, polymer, and DNA mixtures. The emphasis is placed on the theoretical works, particularly models based on the nonequilibrium thermodynamics, although other approaches such as the statistical, kinetic and hydrodynamic approaches are discussed as well. For each mixture, the major theoretical and experimental works are discussed and the research trends and challenges are addressed. Some of the challenges include a need for combining various methods to develop a comprehensive theoretical model or at least to try to understand the differences and pros and cons of each approach. Thermodiffusion and ordinary diffusion coefficients are scarce in some mixtures such as binary DNA, molten metal and metal-semiconductor mixtures and all ternary mixtures. Understanding of the molecular structure of associating mixtures, and modeling of thermodiffusion in such mixtures are also very challenging.

Thermophoresis of charged colloidal particles in aqueous media – Effect of particle size

“…The sign change of D T has been attributed to depend on background temperature [31,32], thermoelectricity [33][34][35], and collective effect [30]. Interestingly, the sign changes of D T were also found for alkali halide aqueous solutions at different background temperatures [36] and for complex associating mixtures [37,38].…”

Effect of thermophoresis on natural convection in a Rayleigh–Benard cell filled with a nanofluid

“…A change in the direction of the thermophoresis force in the system is therefore only observed when a fluid flow is present. In the stationary systems subject to a temperature gradient, thermodiffusion or thermophoresis force always acts in a direction opposite to that of the temperature gradient, e.g., [1,43]. In Fig.…”

“…where U T is related to the thermophoresis or thermodiffusion or thermophoresis coefficient D T as follows [1]:…”

“…In some heat transfer applications, a temperature gradient may exist in the domain. The force exerted on nanoparticles because of a temperature gradient in the fluid is called the thermophoresis force [1]. There is a difference in the response of a nanofluid to a temperature gradient in natural convection in a cavity compared to the forced convection in a laminar or turbulent flow.…”

Estimation of molecular and thermodiffusion coefficients for non‐ideal molten metal alloys and its implication in solidification process

“…Thermodiffusion is utilised for species separation in liquid molten metal alloys, separation of polymer blends, particle and macromolecule manipulation, and for the composition estimation in underground hydrocarbon reservoirs in a porous medium, to name a few. A recent review of advances and applications is given in Ref …”