What is the main difference between positive displacement pump & non positive displacement pump?

Question

Accepted Answer

Positive displacement pumps move fluid by trapping a fixed amount and forcing it into the discharge pipe.

Positive displacement pumps move fluid by trapping a fixed amount and forcing it into the discharge pipe.
They create a constant flow rate regardless of the system pressure.
Examples include reciprocating pumps, rotary pumps, and diaphragm pumps.
Non-positive displacement pumps, like centrifugal pumps, use impellers to increase the fluid's velocity and transfer it to the discharge pipe.
They rely on the system pressure to determine the flow rate.
Examples include centrifugal pumps, axial flow pumps, and mixed flow pumps.

Accepted Answer

Positive displacement pump gives low discharge high pressure . 
Non positive displacement pump gives high discharge low pressure.

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