Molecular dynamic simulation of wet water vapour transport in porous medium

TL;DR

This paper uses a hybrid molecular dynamics and macro-diffusion model to simulate how wet water vapour diffuses through porous media, considering factors like pressure, pore size, and temperature, relevant for environmental and industrial processes.

Contribution

It introduces a combined molecular and macro-diffusion modeling approach to analyze water vapour transport in porous structures, accounting for adsorption and temperature effects.

Findings

Diffusion rate depends on pore size and pressure difference.

Water vapour temperature influences adsorption and diffusion.

Cooling rate affects vapour diffusion and wall adsorption.

Abstract

Studies of the transport of wet water vapour are relevant for various areas of human activity, including the construction and production of building materials, mining, agriculture, environmental safety of technological processes, scientific research. In particular, one of the methods for extracting highly viscous bitumen grades of oil from the subterranean depths is based on the dilution of the contents of the porous medium by means of pumping coolants. The simplest and environmentally friendly coolant is wet steam containing small drops of water. In addition, with the help of heated water vapour, the filtering elements of collectors are cleaned from sediments of the solid phase (for example, paraffins, gas hydrates and ice floes) on the walls of the porous medium. For realistic modeling of the processes of filtration and heat and mass transfer during the injection of wet steam into a porous medium, it is necessary to investigate the characteristics of the interaction of saturated water vapour with individual through-type pores. In this paper, a study was carried out through mathematical modelling of the dependence of the diffusion rate of wet water vapour on the pressure difference outside the pore that occurs when water vapour is injected into a porous medium. The dependencies of the diffusion rate on the pore cross section, the magnitude of vapour adsorption on the pore walls, as well as the effect of water vapour temperature on all these processes were also investigated. Practical interest is the study of the influence of the rate of cooling of water vapour on the diffusion rate and the adsorption of water vapour on the wall of the pores. The calculations were carried out using a hybrid type model that combines molecular dynamics and macro-diffusion approaches to describe the interaction of water vapour with individual pores.