Non-equilibrium molecular dynamics simulation to evaluate the effect of confinement on fluid flow in silica nanopores. (1st June 2022)

• Record Type: Journal Article
• Authors: Asai, Pranay; Jin, Jiaqi; Deo, Milind; Miller, Jan D.; Butt, Darryl
• Is Part Of: Fuel. Volume 317(2022)
• Publication Date: 2022-06-01
• Subjects: NEMD -- Confinement -- Silica pores -- Slip flow -- Stick length -- Nanopores; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.123373
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Flow of hexane methanol and water in silica nanopore with size 2–8 nm is studied. Molecular dynamics to study of fluid-wall interactions and geometric effects. Efficient flow simulation method to calculate the flow deviation factors. Results show reduced flow in silica nanopores. Abstract: The flow of fluids in nano-confinement has applications in separations, water purification, medical systems and in the recovery of fluids in petroleum systems. It is believed that fluids do not obey continuum laws when flowing in nanopores (or in confinement). This paper attempts to shed light on various nano confinement effects such as fluid-wall interactions, pore size and molecular geometry, using molecular dynamic simulation. Water, hexane, and methanol flow behaviors were simulated for pore diameters ranging from 1 to 8 nm. In addition to the density analysis of the confined fluids, the fluid flows in saturated nanopores were simulated by the sectional flow method. Water and methanol molecules were completely stabilized in the 1 nm pore. Hexane molecules could not enter the 1 nm pore, due to geometric considerations. For the 2 – 8 nm pores, all fluids showed reduced flow rate compared to the Hagen–Poiseuille flow, due to an interfacial molecular layer stabilized at the pore surface. Flow reduction observed in these studies is contrary to significant flow enhancements observed for fluid flow in carbon nanotubes of similar dimensions. Water flow showed almost constant stick length for all the pore sizes. Methanol flow had the largest stick length. Hexane flow was reduced because of overcrowding of molecules at the pore surface. The effect of confinement diminished with an increase in pore diameter.