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Cavitation and speed: Effect of increasing pump rotational speed on NPSH required (NPSHr). Assume similar operating conditions within a pump family and incompressible flow. Choose the correct statement about how NPSHr changes with speed.

Difficulty: Easy

NPSHr decreases as speed increases.
NPSHr increases with speed due to higher inlet losses and acceleration effects.
NPSHr is independent of speed.
NPSHr becomes zero at the best efficiency point (BEP).

Correct Answer: NPSHr increases with speed due to higher inlet losses and acceleration effects.

Explanation:

Concept

NPSH required grows with speed because inlet velocities and losses increase, raising the cavitation margin needed to avoid vapor formation.

Affinity/Scaling insight
For geometrically similar conditions, higher N increases characteristic velocities and losses at the eye, typically increasing NPSHr.

Cavitation and speed: Effect of increasing pump rotational speed on NPSH required (NPSHr). Assume similar operating conditions within a pump family and incompressible flow. Choose the correct statement about how NPSHr changes with speed.

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