Question

Power required by a centrifugal pump is proportional to (Where, D = diameter, N = rpm):

• A. \(\text{\( N^2D^3 \)}\)
• B. \(\text{\( ND^2 \)}\)
• C. \(\text{\( N^2D \)}\)
• D. \(\text{\( N^3D \)}\)

Hint:

For centrifugal pumps, power requirement follows \( P \propto N^3D \), meaning higher speeds require exponentially more power.

Answer 1

The Correct Option is D

Step 1: Understanding pump power requirement. - Power (\( P \)) in a centrifugal pump is proportional to: \[ P \propto N^3D \] where: - \( N \) = rotational speed (rpm), - \( D \) = diameter of impeller.
Step 2: Explanation of incorrect options.
- (A) \( N^2D^3 \), (B) \( ND^2 \), (C) \( N^2D \): These do not match the cubic dependency of power on rotational speed.
Step 3: Selecting the correct option. Since power varies as \( N^3D \), the correct answer is (D) \( N^3D \).