Numerical modelling of coupled heat and momentum transfer in a porous medium saturated by a supercritical fluid

Abstract

This paper addresses the coupled heat and mass transfer in a one-dimensional porous medium saturated with a van der Waals supercritical fluid and subjected to a boundary heat flux. This one-dimensional study is the basis and preparatory step in order to outline all the new physics involved in this study before a complete two or three dimensional investigation of more complex systems is undertaken. We use the finite volume method as the basis for the numerical modeling of the system. We observe different hydrodynamic regimes as a function of the proximity to the critical point which clearly influence the physical phenomena occurring in the supercritical fluid. Two cross-over values delimitate three regimes namely (i) pure supercritical regime (based on thermoacoustic effect or Piston Effect (PE) as in pure fluid), (ii) a mix of porous (by pressure gradients inducing temperature gradients in the bulk) and PE effects, and (iii) pure porous diffusion effects (by pressure gradients in the bulk and in the boundary layer). The two crossovers are shown to be dependent only on the ratio of the acoustic wave propagation time to the viscous diffusion time at the pore scale. The results addressed in this study open the unexplored field of porous media saturated by supercritical fluids.