How do pumps use energy to raise, move, or compress fluids?

Pumps are engineering devices that impart energy to fluids to raise, move, or compress them. They are generally classified by the method used to transfer this energy:1

• Volumetric Displacement: Positive displacement pumps, such as reciprocating (piston, plunger, diaphragm) or rotary (gear, lobe, screw, vane) types, mechanically trap a specific volume of fluid and force it from the inlet to the outlet, increasing pressure as the available volume decreases.12
• Addition of Kinetic Energy: Kinetic pumps, such as centrifugal pumps, use a rapidly rotating impeller to accelerate the fluid. This kinetic energy is subsequently converted into pressure energy, often by slowing the fluid within a widening casing.13
• Electromagnetic Force: Used for fluids that are good electrical conductors (like liquid metals), these pumps pass a current through the fluid within a magnetic field, creating an electromagnetic force that drives the flow, similar to an electric motor.14

Other specialized methods include jet ejectors, which use high-velocity fluid streams to create suction, and hydraulic rams, which convert the energy of a moving water column into pressure via a "water hammer" effect.4