4. Agitation and Mixing Tests on a small scale tank 0.3 m diameter (Rushton impeller, diameter 0.1 m) have shown that a blending process between two miscible liquids (aqueous solutions, properties approximately the same as water, i.e. viscosity 1 mN s/m2, density 1000 kg/m3) is satisfactorily completed after 1 minute using an impeller speed of 250 rev/min. It is decided to scale up the process to a tank of 2.5 m diameter using the criterion of constant tip-speed. (a) What speed should be chosen for the larger impeller? Answer: 20.8 rev/min (b) What power will be required? Answer: 9.8 W (c) What will be the blend time in the large tank? Answer: 1.15 min