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 in to the pumpas the cavity on the suction aspect expands and the liquid flows from the discharge because 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 definitely that positive displacement pumps will move liquid at 
the same swiftness regardless of the strain on the inlet end and centrifugal pumps won’t