How do you select impellers for different bioreactor applications?

Impeller selection balances mixing, oxygen transfer, and shear stress. Rushton disc turbines provide high shear and good gas dispersion but high power consumption - suitable for microbial fermentation. Pitched blade turbines offer axial flow with moderate shear - good for blending. Hydrofoil impellers (A315, Elephant Ear) provide efficient bulk mixing with low shear - ideal for mammalian cells. Marine propellers give good axial mixing at low shear. Multiple impeller configurations (e.g., Rushton bottom + hydrofoil top) optimize both gas dispersion and mixing. Selection considers: organism sensitivity, viscosity (shear-thinning media need different approaches), gas dispersion requirements, and scale. CFD modeling aids impeller design optimization.