IntermediateTopic 63 of 105Thermodynamics & Fluids
Pumps
Add energy to fluids; operating point is where pump curve meets system curve.
In depth
Centrifugal pumps use an impeller to convert shaft power to fluid head; positive displacement pumps (gear, piston) deliver fixed volume per revolution. P_hydraulic=ρgQH; efficiency η=P_h/P_shaft. Operating point is intersection of pump and system curves.
Key points
- Pump curve H-Q
- BEP best efficiency point
- Series and parallel operation
ExampleA pump delivering 0.05 m³/s at 30 m head needs ≥14.7 kW hydraulic power.
A pump is designed to work where its curve meets the system curve, so this operating point decides flow, head and power in practice.
What is Pumps?
Add energy to fluids; operating point is where pump curve meets system curve.
Why is it important to understand pumps?
A pump is designed to work where its curve meets the system curve, so this operating point decides flow, head and power in practice.
What is the operating point?
The intersection of the pump's head-flow curve with the system's resistance curve, where the pump head equals the system head loss.
Why does closing a valve change the flow?
It increases the system resistance, which moves the system curve up, and the operating point shifts to a lower flow.
How is Pumps used in practice?
Typical applications include selecting a pump whose operating point gives the required flow in a water system, predicting how throttling a discharge valve changes flow and matching a pump to a system with changing demand.
What should I learn before Pumps?
Study "Pipe networks" first (topic 62 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
What are the key points of Pumps?
Pump curve H-Q. BEP best efficiency point. Series and parallel operation.
Can you give an example of Pumps?
A pump delivering 0.05 m³/s at 30 m head needs ≥14.7 kW hydraulic power.
What comes after Pumps?
The next topic is "Pump affinity laws", which builds directly on this one.
How difficult is Pumps?
It is classed as Intermediate in Thermodynamics & Fluids (topic 63 of 105). It is an intermediate topic. Work through the beginner topics in Thermodynamics & Fluids first.