Observations of flow patterns in a spray dryer

Experiments have been performed on a pilot scale, cylinder-on-cone spray dr yer fitted with a vaned-wheel atomiser to observe air flow patterns, with a nd without water spray. A combination of tufts, smoke streams and a laser l ight sheet, was used to provide information about regions of recirculation, flow stability, spray trajectories and wall deposition. While atomiser-ind uced swirl dominated the flow patterns under typical operating conditions, some instability was observed, although different in type, for situations w ith and without atomiser rotation. Clockwise eddies were observed to form a nd collapse between the wall and the strongly anti-clockwise swirling core created by anti-clockwise atomiser rotation. Without swirl, large portions of the recirculation zones at the walls were observed to have a weak tenden cy to change randomly between clockwise, anti-clockwise and chaotic behavio ur.