Using CFX4, a computational fluid dynamics program, the gas flow pattern, the droplet trajectory and the extent of drying were calculated for spray drying of a milk with a rotary disk in a spray chamber of 140 cm in diameter and 170 cm in height. Due to the cone of the chamber, whose cross sectional area became smaller toward the outlet, a recirculation flow was formed in the chamber pointing downward in the center and upward near the wall. The gas flow pattern was significantly affected by the droplets ejected from the rotating disk. The smaller droplets descended downward not far from the axis, medium sized droplets were swept into the recirculation flow, and even larger ones were little affected by the recirculation flow, travelling downward near the wall. The center of recirculation flow moved upward and toward the wall as the vane angle of the air disperser was increased from 0 to 30 and 45 °. An increase of the vane angle increased the swirling intensity and consequently the droplets flew in a larger circle resulting in an increase of the residence time. On the other hand, the droplets became more likely to hit the wall with the vane angle increase.