Modelling relaxation processes for fluids in porous materials using dynamic mean field theory: application to pore networks

Abstract

We present an application of a recently developed dynamic mean field theory to the study of relaxation dynamics in adsorption and desorption from pore networks. The theory predicts the evolution of density distribution in the system, based on an underlying free energy functional from static mean field theory and the system evolves to equilibrium or metastable equilibrium states consistent with the static theory. The theory makes it possible to follow the evolution of the density distribution with time in response to a change in the bulk pressure or chemical potential. We compare uptake dynamics for a 2D slit pore network with that in a single slit pore. We see more rapid uptake dynamics in the pore network in some cases, due to the greater access of the pore space to the bulk. We also observe that the formation of liquid bridges can slow down the mass transfer in the pore network in certain situations.