Flow-Driven Release of Molecules from a Porous Surface Explored Using Dynamical Density Functional Theory
Journal
Journal of the Taiwan Institute of Chemical Engineers
Journal Volume
117
Pages
26-38
Date Issued
2020
Author(s)
Abstract
We investigate the release of hard-sphere-like molecules from a porous medium to a continuum fluid using dynamical density functional theory. The hard-sphere interactions are employed on the basis of the weighted density approximation. The model porous medium is assumed as a planar wall and molecules are loaded in the medium at an effective density. An equivalent surface density of molecules is applied to determine the surface flux taking into account both the effective medium density and near-wall density fluctuations in the fluid. In the presence of an external flow field which is parabolic near wall, a diffusion layer similar to the mass transfer boundary layer is developed downstream. We compare the effects of various physical parameters including molecular diffusivity, velocity field, interfacial mass transfer resistance, interfacial normal velocity, and effective medium density. We demonstrate that wall-mediated hard-sphere interactions impact the density distribution of released molecules such that the diffusion layer thickness is increased and the near-wall density fluctuation is observed. Moreover, for transient release with a finite amount of loaded molecules, the maximum concentration of the released molecules at different times is identified as a function of distance from the surface. The information gained in this study would be useful to predict the desorption or release efficiency of molecules from a given porous material subjected to various physically-relevant conditions. ? 2020 Taiwan Institute of Chemical Engineers
Subjects
Boundary layers; Diffusion in liquids; Inertial confinement fusion; Molecules; Porous materials; Spheres; Velocity; Density distributions; Diffusion layer thickness; Dynamical density functional theories; External flow fields; Interfacial mass transfer; Maximum concentrations; Molecular diffusivity; Weighted density approximation; Density functional theory
SDGs
Type
journal article