To keep the power input constant for a stirred vessel operating under fully developed turbulent flow conditions (constant power number), if the impeller diameter is increased by 20%, the impeller speed should be decreased by a factor of_________________?

Question

Accepted Answer

(1.2)5/3. For constant power input (constant Power Number), the relationship is $P 	ext{ constant} = N^3 D^5 	ext{ constant}$. If $D$ increases by 1.2, $N$ must decrease by $(1.2)^{-5/3}$.