A positive displacement pump makes a liquid move by trapping a fixed amount 
and forcing (displacing) that trapped volume into the discharge pipe. … Liquid flows in to the pumpas the cavity on the suction part expands and the liquid flows out of the discharge since the cavity decreases.
The most typical type among centrifugal pump may be the radial flow pump. … The main difference between these kinds of pumps and centrifugal is certainly that positive displacement pumps will move liquid at the same velocity regardless of the strain on the inlet end and centrifugal pumps won’t
