What is the effect of increasing impeller speed in a centrifugal pump?

• A. It decreases the discharge pressure
• B. It stabilizes flow rate
• C. It increases the discharge pressure
• D. It causes the pump to overheat

Answer: (C)

Increasing the impeller speed in a centrifugal pump affects the discharge pressure in a significant way. When the impeller spins faster, it imparts more kinetic energy to the fluid being pumped. This increased energy results in a higher velocity of the fluid as it exits the impeller, which leads to an increase in both the flow rate and the discharge pressure of the pump.

The relationship between impeller speed and discharge pressure is rooted in the principles of fluid dynamics. According to the affinity laws, specifically the one related to pump speed, if the speed is increased, the flow rate and head (which corresponds to discharge pressure) will increase proportionally, assuming that other factors remain constant. This is critical in applications where meeting a certain pressure is essential for system performance.

In summary, increasing the impeller speed will increase the energy transferred to the fluid, resulting in higher discharge pressure, making this the correct answer.