High-resolution thermography and modelling allows for improved characterization of drying sessile single droplets

Abstract

Single droplet drying experiments help to understand droplet drying behavior during spray drying. In this study, high-resolution thermography and high-speed camera monitoring were used to characterize drying behavior of sessile single droplets containing solutes. Selected solutes were maltodextrin with a dextrose equivalent of 6, 21, and 38, whey protein isolate and galacto-oligosaccharide. A heat and mass transfer-based model was developed to describe the drying kinetics of the sessile droplets, assuming ideal shrinkage. This model accurately predicted the drying behavior of the droplets, including the droplet temperature during the constant rate period, the duration of this period, and the final droplet temperature. Remaining differences between measured and predicted droplet temperature are explained by skin formation and subsequent morphological development. Tracking temperature with thermography allows to more accurately follow and understand drying behavior, including morphology development of sessile droplets. It makes it possible to develop better models to translate the obtained insights to spray drying behavior.