The power of screw water chiller is relatively larger than that of scroll chiller. It is mainly used in central air conditioning system or large industrial refrigeration. It can be divided into two categories.

1.Twin-screw refrigeration compressor is an energy-adjustable fuel injection compressor. Its three continuous processes of inspiration, compression and exhaust are realized by periodic volume change of a pair of intermeshing Yin and Yang rotors in the body when they rotate. Generally, the Yang rotor is the active rotor and the Yin rotor is the driven rotor. Main components: double rotor, body, main bearing, shaft seal, balance piston and energy regulating device. The capacity is 15-100% stepless regulation or two-stage or three-stage regulation, adopting the way of increasing or reducing load of oil pressure piston. Conventional use: both radial and axial rolling bearings; open type with oil separator, storage tank and oil pump; closed type for differential pressure oil supply for lubrication, injection, cooling and driving sliding valve capacity adjustment of piston movement. Inhalation process: The gas enters the interdental volume of Yin and Yang rotors through the intake. Compression process: When the rotor rotates, the volume between the teeth of Yin and Yang rotors is connected (V-shaped space). Because the teeth mesh with each other, the volume gradually reduces and the gas is compressed. Exhaust process: The compressed gas moves to the exhaust port to complete a working cycle.

2. Compression is generated by the engagement of an active rotor and two star wheels. Its three continuous processes of suction, compression and exhaust are realized by periodic volume change of rotor and star wheel when they rotate. The number of rotor teeth is six and the star wheel is eleven. The main components are a rotor, two star wheels, body, main bearing and energy regulating device. The capacity is 10% to 100% stepless regulation or three-stage or four stage regulation. Inhalation process: The gas enters the rotor slot through the suction port. With the rotation of the rotor, the star wheel enters the meshing state with the rotor slot in turn, and the gas enters the compressed cavity (the closed space formed by the rotor slot surface, the inner cavity of the housing and the tooth surface of the star wheel). Compression process: As the rotor rotates, the volume of the compression chamber decreases. The gas moves to the exhaust port with compression to the front of the compression chamber. Exhaust process: When the front edge of the compression chamber is turned to the exhaust port, the exhaust starts and a working cycle is completed. Because of the symmetrical arrangement of the star wheel, the cycle will be compressed twice in each rotation cycle, and the exhaust volume correspondingly is twice as much as the exhaust volume of the cycle mentioned above.