Study of transport of fluids under nano-confinement using non-equilibrium molecular simulation
File(s)
Author(s)
Xu, Weilun
Type
Thesis
Abstract
The boundary-driven non-equilibrium molecular dynamics (BD-NEMD) has been introduced to evaluate the mass transport coefficients of fluids in nano-confinement. In contrast to the traditional equilibrium simulation route, BD-NEMD directly measures flux and thermodynamic gradients between upstream and downstream of a porous media, which leads to accurate transport parameters while demanding less computational cost. In this work, the use of BD-NEMD on nano-confined fluids are investigated and extended to binary fluids. A novel technique that evaluates steady-state adsorbed densities at pore entry/exit using adsorption isotherms is proposed. By comparing with the traditional EMD method, it is shown that BD-NEMD is robust and suitable for the study of the transport of dense fluids in nano-confinement.
BD-NEMD is further used to investigate the effect of the geometry and morphology of porous solids on the transport of nano-confined fluids. It is demonstrated that the fully mutualized plug-like flow and fast transport which is commonly observed in slit pores do not present itself in rugose pores. Depending on the choice of pore model, transport diffusivity is observed to drop up to two orders of magnitudes; It is also observed that pore selectivity varies with rugosity level, which greatly alters the adsorption/transport of multi-component fluids. The different solid models used in this work are generalised using pore characteristic parameters. It is demonstrated that the transport coefficients are correlated to these parameters. This work has a direct impact on the understanding and modelling of unconventional hydrocarbon recovery and flow in organic shale rocks.
BD-NEMD is further used to investigate the effect of the geometry and morphology of porous solids on the transport of nano-confined fluids. It is demonstrated that the fully mutualized plug-like flow and fast transport which is commonly observed in slit pores do not present itself in rugose pores. Depending on the choice of pore model, transport diffusivity is observed to drop up to two orders of magnitudes; It is also observed that pore selectivity varies with rugosity level, which greatly alters the adsorption/transport of multi-component fluids. The different solid models used in this work are generalised using pore characteristic parameters. It is demonstrated that the transport coefficients are correlated to these parameters. This work has a direct impact on the understanding and modelling of unconventional hydrocarbon recovery and flow in organic shale rocks.
Version
Open Access
Date Issued
2024-04
Date Awarded
2024-10
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Müller, Erich A.
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)