Question

In a mixing tank operating at a very high Reynolds number 104, if the diameter of the im peller is doubled, keeping other conditions constant, the power required increases by a factor of:

• A. $\frac{1}{32}$
• B. $\frac{1}{4}$
• C. 4
• D. 32

Hint:

Remember the power-law relationship for impeller diameter in turbulent mixing.

Answer 1

The Correct Option is D

Power required in high Reynolds number mixing is proportional to the fifth power of the impeller diameter:

\( P \propto D^5 \)

Doubling the impeller diameter results in a \( 2^5 = 32 \)-fold increase in power requirement.