CFD-DEM -DDM Model for Spray Coating Process in a Wurster Coater

Abstract

A multiscale model by coupling computational fluid dynamics (CFD) with a discrete element model (DEM) and discrete droplet model (DDM) is developed to simulate a lab-scale Wurster coater. Two case studies are conducted to study the effect of particle shape in the system. In the first case study, 45,000 spherical particles are coated for 5 s while for the second case study, a mixture of 22,500 spherical particles and 22,500 cylindrical particles is simulated. The residence time distributions (RTD) of particles in different spray zones are compared, and the best spray zone is derived by analysing the positions of spray droplet-particle contacts. The simulation results show that the RTD of the particles within an accurate spray zone can provide valuable information on the final product's particles size distribution. Furthermore, the coefficient of variation (COV) for the coating mass received by the particles is studied for both case studies.

Keywords: CFD-DEM; Fluidized bed; Simulation; Spray coating.