Two-equation continuum model of drying appraised by comparison with pore network simulations

A two-equation non-local-equilibrium (NLE) continuum model of isothermal drying is assessed by comparison with pore network simulations considering a rigid capillary porous medium that is fully saturated initially. This continuum model consists of a transport equation for the liquid and of a transport equation for the vapor. The two main variables are the liquid saturation and the vapor partial pressure. The two equations are coupled by a phase-change term and mass transport at the medium surface is modeled by considering the individual boundary conditions for the two continuum model equations. The macroscopic parameters that appear in the NLE continuum model include classical parameters such as the effective liquid and vapor diffusivities, as well as non-classical and new parameters such as the specific interfacial area and the fraction of dry surface pores. These parameters are determined for the porous microstructure corresponding to the cubic network used to perform the pore network simulations. The results obtained by the two-equation NLE continuum model are compared with pore network simulation data. Comparisons reveal that the two-equation NLE continuum model can capture with a reasonable degree of accuracy the NLE effect as well as the phase distributions and drying kinetics of the pore network model drying simulations.