(98f) Effect of Particle Size and Shape On Just Suspended Impeller Speed

The goal of this study is to determine the effect of particle size and shape in solid-liquid suspensions. Three shapes were investigated: spheres, cylinders, and plates. These experiments wereperformed holding the density of the material constant and using a single tank and impeller geometry. It was found that at equal particle mass for a range of mass fractions, the spheres were the most difficult to suspend requiring higher stirrer speeds than both rods and plates.  In addition the required speed to just suspend rods and plates was very similar.  It was found that the side length of the plate has a bigger effect on Njs than thickness of the plate and the length of the rod has little effect on Njs, while diameter has much more significant effect.  These results also show that there is a maximum Njs with respect to the characteristic diameter defined by volume divided by area which occurs between approximately 0.5 to 1mm for various shapes.

New correlations were developed for the three shapes of Aluminum tested in this study.