462777 Comparison and Validation of Coupled CFD-DEM and CFD-TFM Simulation Predictions for a Laboratory-Scale Wurster-Coating Process
Predictions from both approaches are validated against the experimental measurements reported by Li et al. [AIChE J. (2015), 61(3), 756-768]. The CFD-DEM simulations were performed using the XPS code (eXtended Particle System, developed internally at RCPE) coupled with commercial CFD software AVL Fire™ (AVL List GmbH Graz, Austria). The CFD-TFM simulations used Ansys Fluent™ (ANSYS Inc. Canonsburg, USA). The objective of this study to determine which modeling methodology is best-suited to simulate the Wurster coating process. More specifically, the ability of CFD-TFM simulations to generate the desired residence-time-distribution data in various regions of the coater is contrasted to the more-expensive CFD-DEM method.
For both CFD-DEM and CFD-TFM approaches, the bead flow velocities, residence time in various zones, and the bead-cycle-time distributions were measured to allow direct comparisons to Li et al. The present results, using both CFD-DEM as well as CFD-TFM, agree quantitatively and qualitatively with the experimental results given by Li et al. However, a comparison of the clustering and bubbling dynamics reveal significant differences between the CFD-DEM and CFD-TFM models. Although it is difficult to precisely identify the source of these differences, it can be stated that the CFD-DEM predictions are more visually similar to the flow of actual beads.
Simulations using half (180o) and quarter (90o) models, taking advantage of azimuthal symmetry, are also performed—such a strategy would be important to enable simulation of larger-scale Wurster coaters. The CFD-DEM method shows better agreement between the full- (360o), half-, and quarter-sized systems, whereas the CFD-TFM approach was not amenable to this type of geometric idealization. Therefore, CFD-DEM has been demonstrated to be better suited to simulate the current Wurster-coating