Unsteadiness and resolution effects in experimentally verified simulations of a spray drying process

In this work, time-resolved three-dimensional numerical simulations supported by laboratory experiments aim to provide complementary information of the spray drying process, revealing pivotal details about the flow and particles dynamics. A drying model was implemented in the OpenFOAM open-source code and large-eddy simulations (LES) of the flow were performed on a BÜCHI Mini-spray dryer using real working conditions and input parameters. This work involved simulating a realistic number of particles (10,000 particles/s), higher than those commonly used. The simulation allowed to describe the average strong recirculation in the drying chamber, highlighting the wide spread of the residence time of each particle and how it affected its distribution. The percentage of product loss due to wall contamination is in good agreement with those in the experiment, showing that the simulations are reliable. This study illustrated the importance of unsteady and well-resolved simulations to gain insight into how flow characteristics affect particle trajectories and the product quality, giving information complementary to experimental measurements. Our observations also showed the importance of an appropriate resolution to describe flow features, those identification is crucial to design new devices with greater efficiency.