Physics-based modeling of simultaneous heat and mass transfer intensification during vacuum steaming processes of starchy material

Abstract

Simultaneous heat and mass transfers in reactive porous media such as starchy material are important phenomena, which occur during hydrothermal processes. The driving force in this type of material is not governed only by the moisture potential gradient (non-equilibrium condensation rate) but also by a hydric need required to change phase (melting). In this paper we compared in simulation two processes at the temperature of 120°C. The first one is named the RP-HMT process for Reduced Pressurized-Heat Moisture Treatment. The second is the DV-HMT process for Direct Vapor-Heat Moisture Treatment. In the first process transfer phenomena are amplified due to the presence of an initial vacuum before injection of live steam into the reactor.A model of the processes is implemented and solved using COMSOL multiphysics software. We observed that heat transfer intensification during RP-HMT reduces the resistance of air, and consequently facilitates the diffusion of steam into the product. The computed values confirm those obtained experimentally. A study of the model sensibility to the parameters was investigated. The simulation results show also that the influences of the estimated parameters strongly depend on the hydrothermal processes. They are more important for the RP-HMT than for the DV-HMT.