Mass transfer through vapour–liquid interfaces: a molecular dynamics simulation study

ABSTRACT

A quasi-stationary molecular dynamics simulation method for studying mass transfer through vapour–liquid interfaces of mixtures driven by gradients of the chemical potential based on the dual control volume (DCV) method is described and tested. The rectangular simulation volume contains three bulk domains: a liquid domain in the middle with vapour on each side such that there are two vapour–liquid interfaces. The mass flux is generated by prescribing the chemical potential in control volumes in the vapour domains close to the outer boundary of the simulation volume. The simulation method was applied for studies of two binary Lennard-Jones mixtures: one in which a strong enrichment of the low-boiling component at the vapour–liquid interface is observed and another in which there is practically no enrichment. The two mixtures differ only in the dispersive interactions; their bulk diffusion coefficients are similar. Furthermore, the prescribed chemical potential difference was the same in all simulations. Nevertheless, important differences in the mass flux of the low-boiling component were observed for the two mixtures at all studied temperatures which might be related to the enrichment at the interfaces.

GRAPHICAL ABSTRACT

Keywords:

• Vapour–liquid interface
• mass transfer
• binary Lennard-Jones mixture
• molecular dynamics
• enrichment

Acknowledgements

The authors gratefully acknowledge funding of the present work by the ERC Advanced Grant ENRICO (grant agreement No. 694807). The simulations were carried out on the ELWE supercomputer at Regional University Computing Center Kaiserslautern (RHRK) under the grant TUK-MTD. The present research was conducted under the auspices of the Boltzmann-Zuse Society of Computational Molecular Engineering (BZS).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by ERC Advanced Grant ENRICO (H2020 European Research Council) [grant agreement No. 694807].