Capozzi, Luigi and Boccardo, Gianluca and Barresi, Antonello A. and Pisano, Roberto (2016) Computer-aided property estimation of micro-particles in packed-beds for freeze-drying applications. In: The 20th International Drying Symposium, 2016-08-07 - 2016-08-10.
Full text not available from this repository.Abstract
The governing equations for heat and mass transfer in porous media depend on packed-bed characteristics. This study proposes the use of computer simulations for the calculation of the porosity, tortuosity and permeability of the packed-bed. In particular, realistic geometric packing arrangements were generated by using a discrete element method particle simulation code that allows a detailed description of interactions between the frozen micro-particles during their loading into a cylindrical container. Once the packed-bed has been generated, its porosity was easily determined as the fraction of void volume over the total one. Furthermore, CFD simulations at the pore-scale were performed so as to calculate its true permeability and tortuosity. All the simulations were carried out within laminar Stokes flow, where neither turbulence nor inertial effects are present. While it is true that freeze-drying is characterized by Knudsen (or transition) flow regime, here CFD simulations were only used to calculate the geometrical properties of the packed-bed which are independent of the flow regime considered. These properties have then been used by a two-dimensional model to describe heat and mass transfer (under Knudsen regime) during freeze-drying of packed-beds made of frozen micro-particles. The impact of particle size and its distribution on process performance was finally investigated.