COMPUTATIONAL FLUID-DYNAMICS MODELING OF VERTICAL PNEUMATIC CONVEYING DRYERS

At present, there are no fully reliable design models for pneumatic conveying dryers. SPS have carried out experiments to find particle velocities, heat transfer and drying rates in a vertical unit, and have developed a model based on stepwise integration up the tube. Results were promising, but drying rates were underpredicted near the feed point. Computational fluid dynamics (CFD) techniques, using the FLOW3D program, were employed to model the feed point region. Particle trajectories, gas velocities and temperatures were calculated. A large dead zone near the feed point was revealed and the hold-up in this was estimated. The model predicted two previously unexplained experimental observations; higher than expected particle velocities up to 0.5 m above the feed point, and 'dipping' of solids entering the drying tube. A wide range of further applications for CFD techniques can be envisaged.