Implications of Molecular Thermal Fluctuations on Fluid Flow in Porous Media and Its Relevance to Absolute Permeability

Abstract

This paper addresses the challenge related to the understanding of varying absolute permeability when forcing fluid (mostly water is considered) through a porous medium at varying system temperatures. It is assumed that the total energy dissipation splits into two contributions, a viscous part and a thermal part. These two energy dissipation channels will exactly balance the supplied external energy. The thermal part has not been considered previously regarding forced water flow through porous media, and it is substantiated theoretically by comparison with the well-known Ludwig–Soret effect. It is based on a hypothesis that the flowing water is dissipating molecular kinetic energy to heat (thermal dissipation) due to an asymmetric spatial velocity distribution up- and downstream the solid matrix. Based on previous theoretical calculations, an expression can be derived showing that thermal dissipation will increase proportional with the total inner surface area of the porous medium and the square root of a...