Modeling the Soret Effect in Dense Media Mixtures

Abstract

A basic aim of this paper is to provide, as much as possible, a comprehensive and unambiguous description of the Soret effect in dense media. To this end, the available literature was examined for unifying themes; the themes found are presented. Many trends in the behavior of thermal diffusion coefficients are found to be correlated to equation-of-state properties. The evolutionary paths of media undergoing heating have the essential constraint of positive entropy production, as expressed by the theoretical relations of nonequilibrium thermodynamics; these are summarized. Also given are the relations between thermodynamic forces that define the path attractor states of media mixtures under steady heating conditions. Data references are given; almost all the available data relates to these asymptotic steady attractor states. There is little or no data available corresponding to the transient paths that are explicitly more dependent on the species diffusive transport mechanisms (rates). The concept of "heats of transfer" to express the thermal diffusion factors is verified to be generally valid for a slight modification of the defining relation as commonly presented. The heats of transfer are equivalent to an extension of kinetic theory thermal diffusion ratios. A discussion on the perspectives needed to properly form generic thermal diffusion models that are valid for any particular situation is given.

Experimental approaches to study thermodiffusion – A review

“…A detailed review of the various theoretical models that have been employed to study thermodiffusion has been recently presented in Refs. [36,37]. On the experimental front, several techniques to investigate thermodiffusion have evolved.…”

On the microscopic origin of Soret coefficient minima in liquid mixtures

“…We provide here a proof of principle and demonstrate that S T minima can exist in even the simplest of mixtures, as exemplified by a binary LJ mixture in which the components differ by only the interaction parameter . The concentration dependence of the S T is, at least for simple mixtures, typically attributed to the cross-interactions between unlike particles [22] -a notion sustained in recent reviews [7,46,47]. For dense supercritical LJ mixtures with cross-interactions given by ) line: a liquid-liquid mixture for x l < x 1 < 1 where x l corresponds to the liquidus; a liquid-solid coexistence region x s ≤ x 1 ≤ x l where x s corresponds to the solidus; and a solid-solid mixture for 0 < x 1 < x s .…”

The Effect of Temperature on Moisture Transport in Concrete

“…Under the non-isothermal condition, moisture transfer is driven by the moisture gradient, as well as by the temperature gradient. Indeed, if a system at an equilibrium state is subjected to a temperature gradient, a mass motion takes place and the system reaches a new equilibrium state [ 20 , 24 , 31 ]. The flux of moisture under a non-isothermal condition can be expressed: where T is the temperature ( K ) and D HT is the coupling coefficient for mass diffusion resulting from the thermal gradient (kg∙m −2 s −1 K −1 ).…”