centrifugal pump
Thread Content
Excuse me: Why does the head of a centrifugal pump increase when the flow rate of a centrifugal pump decreases?
Please refer to the flow, efficiency and pressure head curves of the pump in "Principles of Chemical Engineering".
What I want to know is why the lift of the regulating valve increases when the flow rate is reduced. Don't look at their curvilinear relationship. Consider it from the perspective of pipeline losses.
It can be seen simply and intuitively from the external characteristics of the pump - the performance curve. From the internal flow law, the conversion problem of the velocity field and the pressure field, the flow rate decreases, the speed becomes smaller, and the pressure increases.
As long as the structure and size of the pump remain unchanged, the head will remain unchanged. Are you saying that the outlet pressure will increase? Outlet pressure and head are different concepts. If the outlet pressure becomes larger and the flow rate becomes smaller, the outlet pipeline is blocked.
Every pump has a curve. It should be easy to understand by looking at the curve!
Reducing the flow rate on the pipeline through the regulating valve actually reduces the flow rate of the pump. Therefore, according to the flow head curve, the natural head at the low flow end increases.
Your flow rate has decreased, but the power of the pump motor (or diesel engine) has not changed. . . .