Another example is the simulation of an industrial spray dryer for the production of a powder with high lactose content.The dryer was equipped with one cnetral and sveral non-central air inlet channels and with nozzle atomizers. This dryer had serious fouling problems in the bottom part (cone). The simulation as shown in Figure 5 indicated clearly that the powder particles collded with the cone wall whren the airflow reversed in the conical part of the dryer .Under these conditions the particles were not dry enough and were very sticky. Furthermore ,the simulations indicated that the thermal load od the particles atomised in the central air inlet was much higher than that of the particles atomised in the noncentral air inlets due to the temperature distribution in the dryer .According to new simulations , adapting the cone angle would reduce the fouling problem. However, this would be an expensive modification since the height of the building was limited .Reconstruction of the air inlet has now solved the problem ,mainly by changing the diameters of the air inlet channels

Figure 5. Computational simulation of an industrial spray dryer:air humidity and temperature contours; (b) simulated air-flow patterns and particle trajectories.