Simulation of Mass Transport and Phase Transition through Anodic Alumina Membranes Using a Lattice Boltzmann Method

Area of Science:

• Multiphase flow and transport phenomena
• Nanoscale science and engineering
• Computational fluid dynamics

Background:

• Understanding mass transport in nanoporous membranes is crucial for applications like gas separation and storage.
• Transitional flow regimes and surface interactions significantly influence fluid behavior at the nanoscale.
• Existing models often struggle to accurately capture complex phenomena like adsorption and phase change in confined spaces.

Purpose of the Study:

• To develop and validate a two-phase multirelaxation-time lattice Boltzmann framework for simulating mass transport in nanoporous membranes.
• To investigate the influence of rarefied gas dynamics, surface adhesion, and phase behavior on hydrocarbon permeation.
• To provide a predictive tool for optimizing membrane performance based on molecular interactions and flow conditions.

Main Methods:

• Implementation of a two-phase lattice Boltzmann method with multirelaxation times.
• Incorporation of a modified Peng-Robinson equation of state and extended cohesive/adhesive interactions.
• Development of a multilayer adhesive model to capture near-wall density variations and surface effects.
• Simulation of low molecular-weight hydrocarbon transport through anodic alumina membranes under varying pressures (1-6 bar) and Knudsen numbers (0.2-1.2).

Main Results:

• The model accurately predicts mass flux for methane, ethane, and propane, with deviations within 5-15% of experimental data.
• Surface adhesion effects were found to increase mass flux by up to 12% for light gases due to a mobile adsorbed layer.
• The simulation successfully captured capillary condensation phenomena for isobutane, consistent with experimental observations.
• The study highlights the critical interplay between viscous flow, Knudsen diffusion, adsorption, and phase change in nanoscale transport.

Conclusions:

• The developed lattice Boltzmann framework provides a robust and predictive tool for simulating complex gas transport in nanoporous materials.
• Surface adsorption and phase change are critical factors that must be accounted for in nanoscale transport modeling.
• The findings offer valuable insights for the design and application of nanoporous membranes in gas separation and related technologies.