Compare centrifugal pumps and positive displacement pumps.

Centrifugal pumps use kinetic energy transfer via rotating impeller; flow varies with system resistance while head is relatively constant. Best for high flow, low-medium viscosity fluids. Positive displacement (PD) pumps trap fixed volumes and push them through discharge; flow is nearly constant regardless of pressure, ideal for high viscosity, accurate metering, and high-pressure applications. PD types include reciprocating (piston, diaphragm), rotary (gear, screw, lobe). Selection criteria: centrifugal for clean, low-viscosity, high-flow; PD for viscous fluids, precise dosing, or high pressure.