Reaction engineering approach (REA) to modeling drying problems: Recent development and implementations

Among the drying models available in the literature, the REA model (which was first proposed in 1996) is semi-empirical. It was described based upon a basic physical chemistry principle. The ‘‘extraction of water from moist material’’ is signified by applying the activation energy concept. The single expression of the extraction rate represents the competition between evaporation and condensation. It also encompasses the internal specific surface area and mass transfer coefficient, and thus is linked to material characteristics. The REA can be classified into two categories—Lumped (L) REA and Spatial (S) REA—which can be used to deal with drying a material as a whole or considering the local phenomena within the material, respectively. Both models have been proven to be very effective. The REA is effective for generating parameters since only one accurate drying run is required to establish the relative activation energy function. Both internal and external resistances are modeled by the REA. In its lumped format, the REA is employed to describe the global drying rate, while in the S-REA, the REA is used to model the local evaporation rate. This article covers fundamentals of the REA which have not been fully explained, as well as the most recent development and applications. The application of the S-REA as a non-equilibrium multiphase model is highlighted.