- Modelling spray drying is based on behavior of individual droplets involved in the process. The drying history of single droplets is generalized to the entire spray by incorporating drying kinetics equations into Euler-Lagrange models of spray drying process. The morphological evolution of single droplet is determined by parameters of the drying agent (e.g. pressure, temperature, humidity) and properties of solids material in the droplet (e.g. primary particle size, porosity). During the drying process, internal bubble growth may appear in the droplet center. In this study, a novel mathematical model of single droplet containing insoluble nanoscale particles and internal bubble has been developed. The possible causes for bubble inception are discussed and different morphological evolutions are examined. It was found that, in contrast to the cases with no bubble in wet particle, particle temperature remained close to wet bulb during the second drying stage until the final sensible heating period.