Refrigeration Cycle: Positive Displacement Compressors

All positive displacement compressors generate pressure by drawing vapor into a compression chamber, sealing the chamber, and then shrinking the volume of the chamber. There are four common types of positive displacement compressors: 1) Screw Compressors 2) Reciprocating (or Piston) Compressors 3) Rotary Vane Compressors; and 4) Scroll Compressors.

Screw compressors utilize meshing rotors to force the gas into smaller volumes which increases the pressure as the gas passes through the screw compressor.

A reciprocating compressor uses pistons moving back and forth to reduce the volume in a cylinder which increases the pressure of the vapor inside the cylinder.

A rotary vane compressor employs centrifugal force to move vanes inside a rotor that rotates off-center within a cylinder.

A scroll compressor has one fixed scroll and a second rotating scroll. As the rotating scroll moves, the refrigerant vapor is pushed to the center of the two scrolls, causing a reduction in gas volume. Scroll compressors are not used in industrial refrigeration applications.