Efficiency of centrifugal pumps

Centrifugal pumps need a certain backpressure to operate more efficiently and reach their full capacity. However, the physics behind this are not very straightforward. Could anybody share a simplified / intuitive explanation?

4 Likes

Hello!
The physical principle behind how backpressure can increase the efficiency of a centrifugal pump is related to the concept of net positive suction head (NPSH).
The NPSH of a pump is the amount of energy that is available to the pump to overcome the vapor pressure of the fluid and prevent cavitation. A higher NPSH means that the pump has more energy available to it, which can help to improve its efficiency and increase its flow rate.
When a centrifugal pump is operating, it creates a low-pressure area, or vacuum, at its inlet. This low pressure can cause the fluid at the inlet to vaporize, or cavitate, which can reduce the performance of the pump and cause damage to its impeller.
If the backpressure at the discharge of the pump is high enough, it can help to increase the pressure at the pump’s inlet. This increase in pressure can help to increase the net positive suction head (NPSH) available to the pump, which can improve its performance by preventing cavitation.
Additionally, increasing the NPSH will decrease the pressure difference across the impeller which will make the pump work more efficiently and make the flow rate higher.
This increase in backpressure should be within a certain range and not too high, because excessive backpressure can have negative effects on the performance of a centrifugal pump. High backpressure can restrict the flow of fluid through the discharge piping, which can result in a reduction in the flow rate of the pump, increased power consumption and reduced pump efficiency.
The optimal backpressure will rely on the design of the pump and it is important to consult the performance curves to make sure that the pump operates within its optimal range.

3 Likes

Great topic! I am looking into this matter, can you propose any good textbooks or papers?