Mathematical models for the drying of rigid porous materials

This paper presents a resume of literature on theories and mathematical models for drying of rigid porous materials. Key work on drying by soil physicists has been neglected in the engineering drying literature. We have included these works here to bring this literature to the attention of engineers. A new and general model for moisture and energy transport in rigid porous media during drying is presented. It is demonstrated that under certain simplifying assumptions, the general model reduces to less general models which have previously been proposed. Experimental and simulation results are given for the drying of Valentine sand. Under the drying conditions studied, the drying rate during the falling rate period is controlled by the capillary flow of water to an evaporation zone in the porous media. The models simulated here are of varying complexity and rigor. The capabilities and limitations of these models are discussed. On presente dans ce travail un resume des publications relatives aux theories et aux modeles mathematiques sur le sechage des materiaux poreux et rigides. On a neglige de tenir compte, dans les publications technologiques sur le sechage, des travaux de prime importance executes par les physiciens specialises dans les sols; nous incluons ici ces travaux pour que les ingenieurs en soient mis au courant. On presente un modele nouveau et general pour le transport, durant le sechage, de l'humidite et de l'energie; on demontre qu'en faisant certaines suppositions de simplification, le modele general se transforme en des modeles moins generaux qui out deja ete proposes. On presente les resultats des experiences et de la simulation dans le cas du sechage du sable Valentine. Dans les conditions de sechage etudiees, le taux de sechage durant la periode decroissante de celui-ci est regi par le mouvement capillaire de l'eau vers une zone d'evaporation dans les milieux poreux. Les modeles qu'on a simules ont une complexite et une precision variables; on en discute les possibilites et les limitations.

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