CFD modeling and experimental validation of spray drying for inhalable particles

Spray drying is a key technology for producing inhalable particles used in the treatment of respiratory diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. This study presents a comprehensive computational fluid dynamics analysis of the spray drying process, integrating detailed modeling of gas flow, droplet evaporation, and heat and mass transfer phenomena. The model is validated against experimental measurements of temperature fields and particle size distributions obtained from a Büchi B-290 Mini Spray Dryer equipped with a three-fluid nozzle. Results show good agreement between simulations and experiments, confirming the reliability of the modeling approach. A novel criterion based on the local balance between incident liquid flux and evaporation flux is introduced to interpret thermocouple readings, offering a physically consistent framework for comparing numerical and experimental temperature data. The study highlights the importance of resolving internal nozzle dynamics and multiphase interactions to improve the predictive accuracy of numerical models in pharmaceutical spray drying applications.