Influence of the Spout Velocity

The simulation results show that the velocity of the air injected via the nozzle has a strong influence on the fluid dynamics of the whole granulator. 

In Fig. 7.50, snapshots of the particle positions and their velocities after the same process time are displayed. The granulator is cut vertically in the middle, and the central plane and the parts behind that plane are shown. The color indicates the particle velocity blue particles move slowly (v 0.5 m s ) and red particles are fast (v 1.5 m s ). It can be seen from Fig. 7.50 that for all spout velocities the particles are concentrated at the center in the lower part of the Wurster tube. For high spout 

Variable unit Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 

To assess the radial distribution of particles in the granulator, horizontal slices were cut out of the simulated geometry. This was done at two different heights, as shown in Fig. 7.51. The thickness of each of the slices is 10 mm. The first slice is situated in the lower part of the Wurster tube, just around the tip of the injection nozzle. The second 

In slice 2, only a few particles are present (Fig. 7.53). Their movement is directed upwards inside the tube and downwards in the annulus in all three cases. 

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Figures 7.52 and 7.53 show instantaneous particle positions in the two slices, seen from the top. The colors indicate the vertical component of the particle velocity. Red particles are transported upwards, blue particles fall downwards. A comparison can be drawn between the first three case studies to evaluate the influence of the spout velocity on the horizontal distribution of the particles and their vertical velocity component.

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