Compressors are classified as:
The motor windings are cooled by incoming suction vapors.
These have advantage of no leakage, less noise and compactness.
These are classified again as hermetically sealed, semi sealed and open-type
In rolling piston type, roller is mounted on eccentric shaft with single blade.
In rotating vane type with four vanes the rotor is concentric with the shaft.
The machine consists of two helically grooved rotors which rotate in a housing.
This compressor increases pressure of low pressure vapor refrigerant to high pressure by centrifugal force.
It generally consists of an inlet casing, impeller, diffuser and a volute casing.
It is used for refrigerants that require large displacement and low condensing pressure such as R-11 and R-113