The power of the screw chiller is relatively larger than that of the scroll type. It is mainly used in central air conditioning systems or large industrial refrigeration.

　　 (1) Twin-screw refrigeration compressor: Twin-screw refrigeration compressor is an energy-adjustable oil-injected compressor. Its three consecutive processes of suction, compression, and exhaust are realized by a periodic volume change Screw-Type Condensing Unit when a pair of interlocking Yin and Yang rotors in the machine body rotate. Generally, the male rotor is the active rotor, and the female rotor is the driven rotor. Main components: double rotor, body, main bearing, shaft seal, balancing piston and energy adjustment device. The capacity is 15-100% stepless adjustment or two or three-stage adjustment, which adopts the hydraulic piston to increase or decrease the load. Conventional use: both radial and axial rolling bearings; open type with oil separator, oil storage tank and oil pump; closed type for differential pressure oil supply for lubrication, oil injection, cooling and piston movement to adjust the capacity of the slide valve. Inhalation process: The gas enters the interdental volume of the Yin-Yang rotor through the suction port. Compression process: When the rotor rotates, the volume between the teeth of the male and female rotors is connected (V-shaped space). Due to the meshing of the teeth, the volume gradually decreases and the gas is compressed. Exhaust process: compressed gas moves to the exhaust port to complete a working cycle.

　　 (2) Single screw refrigeration compressor

　　 uses an active rotor and two star wheels to produce compression. Its three consecutive processes of suction, compression, and exhaust are realized by periodic volume changes when the rotor and star wheel rotate. The rotor has six teeth and the star wheel has eleven teeth. The main components are a rotor, two star wheels, body, main bearing, and energy adjustment device. The capacity can be adjusted from 10%-100% steplessly and three or four sections. Inhalation process: the gas enters the rotor slot through the suction port. As the rotor rotates, the star wheel sequentially enters a state of meshing with the rotor slot, and the gas enters the compression cavity (the closed space formed by the curved surface of the rotor slot, the inner cavity of the casing, and the tooth surface of the star wheel). Compression process: As the rotor rotates, the volume of the compression chamber continues to decrease, and the gas compresses until the front edge of the compression chamber turns to the exhaust port. Exhaust process: The front edge of the compression chamber is turned to the exhaust port to start exhaust, and a working cycle is completed. Due to the symmetrical arrangement of the star wheels, the cycle will be compressed twice every revolution, and the exhaust volume is corresponding to twice the exhaust volume of the above cycle.