Effects of Impeller Design and Arrangement

Impellers usually enter the vessel from the top however, very large or novel vessels find it useful for the impeller to enter from the bottom or side (Hamby et al.. 

Impellers can be classified into groups based on the liquid viscosity used in the reactor (Hamby et al., 1992). Propellers, turbines, and paddles have a higher tip speed relative to other impeller types and are used for low viscosity Newtonian liquids that are encountered in most processes (Ogut and Hatch, 1988). Propellers are usually operated faster and paddles are operated slower than turbines. The standard three-bladed propeller has poor gas-liquid dispersion and contacting characteristics and will be excluded from further discussion. 

---