Numerical study of single droplet drying in an acoustic levitator before the critical point of time

•CFD simulations are used to study the first drying stage of a levitated droplet.•Secondary effects near the deformed droplet make its solvent evaporate faster.•Internal convection due to the acoustic streaming keeps the binary droplet well-mixed.•The performance of the acoustic levitator is affected by the drying air temperature. When using an acoustic levitator to perform single droplet drying studies, one has to be aware of its significant impact on the heat and mass transfer. In this paper, we propose a model for the first drying stage of an acoustically levitated water droplet containing suspended solids. Both the realistic geometry of the acoustic levitator and the deformation of the levitated droplet are taken into account by our numerical simulations. Empirical data from the literature are used to validate our single droplet levitation and drying model in case of pure water and binary water-maltodextrin droplets. We found that the acoustic streaming inside the levitated droplet has a retarding effect on its critical point of time when the solute forms a solid crust at the free phase boundary. Moreover, the temperature dependence of the sound wave length turned out to have a crucial impact on the performance of the acoustic levitator.