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.
Mechanical Engineering
Hydraulic Machines
Difficulty: Easy
Choose an option
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ANPSHr decreases as speed increases.
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BNPSHr increases with speed due to higher inlet losses and acceleration effects.
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CNPSHr is independent of speed.
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DNPSHr becomes zero at the best efficiency point (BEP).
Answer
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 insightFor geometrically similar conditions, higher N increases characteristic velocities and losses at the eye, typically increasing NPSHr.
Final AnswerNPSHr increases with speed.