A positive displacement pump makes a fluid move by trapping a set amount and forcing (displacing) that trapped volume in to the discharge pipe. … Liquid flows into the pumpas the cavity on the suction aspect expands and the liquid flows out of the discharge since the cavity decreases.
The most common type among centrifugal pump may be the radial flow pump. … The primary difference between these kinds of pumps and centrifugal is definitely that positive displacement pumps will 
move fluid at the same swiftness regardless of the strain on the inlet end and centrifugal pumps will not