A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure.
A scroll compressor has one scroll, or spiral, orbiting in a path defined by a matching fixed scroll. The fixed scroll is attached to the compressor body.
The orbiting scroll is coupled to the crankshaft and orbits, rather than rotates. The orbiting motion creates a series of gas pockets traveling between the two scrolls. On the outer portion of the scrolls, the pockets draw in gas, and then move into the center of the scroll, where the gas is discharged. As the gas moves into the increasingly smaller inner pockets, the temperature and pressure increase to the desired discharge pressure.
A rotary compressor is a type of gas compressor that uses a rotary-type positive-displacement mechanism.
Semi Hermetic Compressor
The semi-hermetic compressor also encloses the motor compressor by Common Housing. It prevents the leakage of the fluid. In a semi-hermetic, the casing is bolted together instead of rigidly welding. It offers limited serviceability; casing can be open to repair motor and other components.