A drying model, named NIZO-DrySim is developed to simulate aspects of drying processes in the food industry. DrySim simulates the gas flow in a spray dryer in two dimensions and calculates the trajectories and the course of the drying process of the atomised particles. The model makes use of computational fluid dynamics (CFD) techniques. It utilises the k-epsilon turbulence model to calculate the gas flow field. The drying of droplets is influenced by both external and internal transport phenomena (from particle surface to surrounding air in the first case and diffusion within particles in the second). The differential equation that describes the diffusion process of spherical particles is solved numerically, simultaneously with the equations for external heat and mass transfer. It is shown that the drying model is an effective tool in giving indications of how to adapt industrial dryers, for example to get a better product quality or reduce fouling problems.