Time-dependent flow patterns in spray dryers : Particle processing

Low-freguency oscillations in the flowfield inside a 1.5 m diameter spray-drying chamber have been measured using a hot-wire anemometer. We have found that the strongest oscillations occur under the conditions predicted by numerical solutions of the time-averaged Navier-Stokes equations, where significant swirl in the inlet air is sufficient to cause vortex breakdown, the formation of a central recirculation zone and a precessing vortex core. In addition, the good agreement between the frequencies of the strongest oscillations measured here (1-3 HGz) and the frequency predicted by the numerical simulation (1 Hz) gives confidence in the procedures used in the simulation