(155b) Scale-up of Solids Suspension - Zwietering or Power per Mass?

Physical and virtual experiments were made on three sized tanks for solid suspensions. The 12”, 20” and 40” tanks had flat bottoms. Hydrofoils of various solidities and pitched blade turbines of several widths were studied in a range of 0.20 < D/T < 0.6. Water was used as the liquid in all tests and various solids were tested in concentrations from 1% to 40% having particles sizes from 80 to 850 microns. Each of the three tanks were equipped with torque cells and video equipment to determine the just off-bottom speed, 90% suspension and the fully suspended criteria. A virtual mixing (CFD) experiment of each physical experiment was also done to identify the fluid momentum properties at the location of the last suspended particles from the bottom. Results will show comparisons of the two suspension models most commonly used today, Zwietering and power per mass.

This is a continuation of our work that we showed at the North American Mixing Conference in June, 2014 at the Sagamore, Lake George, NY.