Vanishing mean volume velocity in isothermal isobaric diffusion of a binary fluid mixture

TL;DR

This paper demonstrates that in isothermal isobaric diffusion of a binary fluid mixture, the mean volume velocity becomes zero in the linear regime, simplifying the understanding of diffusion properties and related thermodynamic factors.

Contribution

It shows that the mean volume velocity vanishes in the linear regime and derives the thermodynamic factor using the uniform partial specific volumes.

Findings

Mean volume velocity vanishes in the linear regime

Partial specific volumes are uniform and constant

Diffusive volume flux is proportional to mass current density

Abstract

It is shown that in isothermal isobaric diffusion of a binary fluid mixture the mean volume velocity vanishes in the linear regime, independent of the equation of state. The partial specific volumes of the two components are uniform and constant in the process of mutual diffusion. The properties lead to a simple derivation of the de Groot-Mazur thermodynamic factor in the diffusion coefficient. The properties also imply that the diffusive volume flux defined by Brenner is proportional to the mass current density, and is therefore not a quantity of independent interest.