Understanding coupled mass-heat transport in fluids by approach-to-equilibrium molecular dynamics

TL;DR

This paper extends the approach-to-equilibrium molecular dynamics method to analyze coupled mass and heat transfer, deriving analytical solutions and validating them with Lennard-Jones liquid simulations across various conditions.

Contribution

It introduces a generalized AEMD framework for coupled heat-mass transport, providing analytical solutions and validation for complex fluid systems.

Findings

Derived analytical time-evolution equations for coupled heat-mass transfer.

Validated the generalized approach using Lennard-Jones liquid simulations.

Estimated generalized diffusivities across different thermodynamic conditions.

Abstract

We present a generalization of AEMD approach, routinely applied to estimate thermal conductivity, to the more general case in which Soret and Dufour effects determine a coupled heat-mass transfer. We show that, by starting from microscopical definitions of heat and mass currents, conservation laws dictates the form of the differential equations governing the time evolution. In particular, we focus to the well specific case in which a closed-form solution of the system is possible and derive the analytical form of time-evolution of temperature and concentration scalar fields in the case in which step-like initial profiles are imposed across a rectangular simulation cell. The validity of this new generalized expression is finally validated using as benchamrk system a two-component Lennard-Jones liquid system, for which generalized diffusivities are estimated in different reduced temperature and density region of phase diagram.