  Drainage and evaporation can occur simultaneously during the drying of porous
media, but the interactions between these processes and their effects on drying
are rarely studied. In this work, we develop a pore network model that
considers drainage, evaporation, and rarefied multi-component gas transport in
porous media with nanoscale pores. Using this model, we investigate the drying
of a liquid solvent-saturated porous medium enabled by the flow of purge gas
through it. Simulations show that drying progresses in three stages, and the
solvent removal by drainage effects (evaporation effects) becomes increasingly
weak (strong) as drying progresses through these stages. Interestingly,
drainage can contribute considerably to solvent removal even after evaporation
effects become very strong, especially when the applied pressure difference
across the porous medium is low. We show that these phenomena are the results
of the coupling between the drainage and evaporation effects and this coupling
depends on the operating conditions and the stage of drying.
