A dual-scale model for describing drier and porous medium interactions

Abstract

A dual-scale modeling approach is proposed to describe the coupling of the drier (large-scale) and the porous medium (macroscale) throughout drying. This model is used to investigate the vacuum drying of a softwood board placed in an experimental vacuum chamber that is heated by two infrared (IR) emitters. The large-scale model provides important information for the drying engineer to assess and tune the performance of the drier. This model allows simulation of the chamber wall and IR emitter temperature evolution, together with changes in the chamber vapor, air, and water mass balances. The comprehensive two-dimensional drying model known as TransPore is used to determine the heat and mass transfer occurring at the macroscale of the board. Finally, four case studies are presented to elucidate the intricate coupling that exists between the chamber technical specifications and the drying behavior of the porous medium. A highlight of the dual-scale model is its ability to predict the condensation on the walls of a poorly insulated vacuum chamber for the case of a weak pump.