Relaxation effects associated with the flow of a dense gas through a porous medium

Abstract

Unsteady processes of gas and Newtonian liquid flow through porous media are usually described within the framework of the standard elastic regime model [1, 2]. At the same time, from general theoretical considerations it is clear that for fairly small characteristic times of variation of the pressure and the seepage velocity the elastic regime model loses its validity and more general relaxation flow models [3, 4] must be employed. It is therefore important to determine the limits of applicability of the elastic regime model. For this purpose the unsteady process of gas flow from one vessel to another through a porous medium has been investigated theoretically and experimentally for small pressure differences and absolute pressures up to 50 MPa. It is shown that the experimental results diverge sharply from the theoretical predictions based on the elastic regime model. It is therefore proposed that for unsteady processes a generalization of Darcy's law with a relaxation kernel be employed. From the results of the experiments it is possible to determine the parameters of the kernel characterizing the internal relaxation processes in the porous medium-dense gas system.