A positive displacement pump makes a liquid move by trapping a fixed amount and forcing (displacing) that trapped volume in to the discharge pipe. … Liquid flows into the pumpas the cavity on the suction side expands and the liquid flows from the discharge because the cavity decreases.
The most common type among centrifugal pump may be the radial flow pump. … The primary difference between these types of pumps and centrifugal 
can be that positive displacement pumps will move liquid at the same acceleration regardless of the strain on the inlet end and centrifugal pumps will not
