Computer Simulation of Hydrodynamics and Mass Transfer of Supercritical Drying of Aerogels in Laboratory and Industrial Scale Apparatuses

Abstract This article presents the results of modeling the hydrodynamics and mass transfer of the supercritical drying process in apparatuses of various volumes. Calculations of hydrodynamics and mass transfer were carried out using the Ansys Fluent software package, exemplified with devices of laboratory and industrial volumes—2 and 70 L, respectively. The modeling aimed to predict the time of supercritical drying and the feasibility of scaling the process. Continuum mechanics principles were employed to model hydrodynamics and mass transfer, treating the multicomponent system as a viscous compressible fluid. The calculation took place in two areas: within a porous body and in the free volume of an apparatus of a certain scale. Additionally, a study was conducted on the hydrodynamics and mass transfer of the process in the presence of a divider, necessary to minimize the formation of stagnant zones in the apparatus. For optimization purposes, the divider calculation was performed separately from the apparatus. The data obtained were then used in subsequent calculations of the hydrodynamics and mass transfer of the process, employing a user-defined function (UDF) written in the C programming language. A preliminary study of the kinetics of supercritical drying in a 2-L apparatus was carried out to assess the possibility of using the proposed mathematical model for an industrial-level apparatus. The simulation demonstrated that the proposed model is capable of describing the process of supercritical drying in devices of various volumes. Furthermore, calculated curves of the kinetics of supercritical drying, profiles of the velocity distribution of supercritical carbon dioxide, and the distribution of the concentration of isopropyl alcohol at various points in time across the cross-section of the apparatus were obtained.