Numerical and experimental validation of a detailed non-isothermal CFD-DEM model of a pilot-scale Wurster coater

Abstract

Even though the Wurster technology is commonly used in the pharmaceutical industry for applying coating to beads, additional research work is still necessary to fully understand and control the process. Various simulation approaches have been used extensively in the recent years to investigate different fluidized beds, with and without spray application. The Computational Fluid Dynamics- Discrete Element Method (CFD-DEM) coupled approach is especially suitable to simulate the coating process because it resolves both the fluid and granular flow, and provides detailed particle-scale information.This paper primarily highlights the ability of the CFD-DEM coupled code to capture the thermodynamics and water mass loading of the gas phase in the Wurster coating application by directly comparing the experimental results with the CFD-DEM simulation results, for four different experimental runs and unscaled particle size. It also reports on the four specially designed experiments, giving the measurements of the air temperature and humidity at four points in the coater.The code is verified as well, using a simple simulation test case, with the objective of ensuring the energy and mass conservation in the CFD-DEM communication protocol.The paper also presents the time-averaged contour plots of temperature, humidity and particle volume fraction distribution for four different experiment/simulation cases and provides insights into their spatial distribution in the Wurster coater.