The Rotary Screw Compressor is another type of positive displacement unit. It was first used in refrigeration in the late 1950s, but it is gaining ground quickly, due to its relative simplicity.
Basically it consists of two helical gears adjusted to each other, one male and the other female, in a stationary enclosure with suction and discharge openings. To make the threads watertight, in most projects, oil is pumped through the compressor, along with the refrigerant.
