Simulation of heat and mass transfer in spray drying

<p/>A survey is given of heat and mass transfer around droplets in spray dryers and the diffusional transport inside them. A calculational model is developed which includes variable diffusion coefficients in the drying liquid and swelling or shrinking of droplets. Calculations for droplets containing soluble solids show how the drying histories of droplets are influenced by three extreme patterns of air circulation and spray dispersion, and by droplet inflation. The influence of these factors on the properties of spray-dried liquid foods are discussed. Furthermore diffusion equations for binary systems are surveyed and diffusion coefficients for super-saturated aqueous maltose solutions are reported.