A new model for a drying droplet

•A new mathematical model for droplet drying.•Analysis of drying of a spray consisting of chitosan dissolved in water.•Validation of the model against experimental data. A new model for droplet drying is suggested. This model is based on the analytical solutions to the heat transfer and species diffusion equations inside spherical droplets. Small solid particles dispersed in an ambient evaporating liquid, or a non-evaporating substance dissolved in this liquid, are treated as non-evaporating components. Three key sub-processes are involved in the process of droplet drying within the new model: droplet heating/cooling, diffusion of the components inside the droplets, and evaporation of the volatile component. The model is used to analyse the drying of a spray consisting of chitosan dissolved in water. After completion of the evaporation process, the size of the residual solid ball predicted by the model is consistent with those observed experimentally.