Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements



Current literature relies almost exclusively on the power number to compare and characterize impellers. Industrial mixing requirements may rely on conditions far away from the impeller. A protocol is proposed to compare impellers designed for turbulent mixing on the basis of impeller hydrodynamic performance and mixing process objectives. A hydrofoil impeller (KPC), and a mixed-flow impeller (45° down-pumping PBT), each at two diameters, were used to test the protocol. Fourteen measures were considered. Five are recommended for full characterization: power number, momentum number, and peak rate of dissipation of turbulent kinetic energy to characterize conditions at the impeller; power at just-suspended speed to compare the efficiency of solids suspension at the bottom of the tank; and point of air entrainment as a measure of turbulence penetration to the free surface. These five measures provide complete information about mixing performance and good differentiation between the impellers and geometries. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2573–2588, 2012