CFD Modeling of Air Flow on Wall Deposition in Different Spray Dryer Geometries

Abstract

Wall deposition is one of the most conventional problems in the spray drying process. The operation of a spray dryer is affected by the wall deposition fluxes inside the equipment. In this study, computational fluid dynamic (CFD) simulation was used to investigate the effect of spray dryer geometry on wall deposition. A CFD model was developed for different geometries of spray dryer with a conical (case A) or a parabolic (cases B and C) bottom. The results implied that the parabolic geometry resulted in a lower deposition rate on the spray dryer walls. A comparison of results using the P-values (F-test) of the air velocity, in the conical and parabolic geometries, showed that there was a significant difference in air stability between them. The flow field in conical geometry case A was significantly more unstable, and parabolic geometry case C produced the most uniform airflow patterns. Moreover, the higher wall shear stress in case C, with lower values of the vorticity, would result in less wall deposition.

Keywords:

• Air flow
• Computational fluid dynamics (CFD)
• Cone geometry
• Parabolic geometry
• Spray dryer
• Vortex
• Vorticity
• Wall deposition
• Wall shear stress

ACKNOWLEDGMENT

The authors greatly appreciate Dr. Meng Wai Woo at the Monash University, Australia, for sharing constructive ideas in CFD part for this study.