The twin screw compressor:

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Twin screw compressor

This is similar to the one screw but contains a couple of intermeshing rotors or screws: male screw has four or five spiral blades and the female screw six or seven helical grooves, 4 - + 6, 5 + 6 or 5 + 7, male-female combinations. As one screw machines, the process is performed in three stages: suction, compression and discharge.

Two screws compressors contained in the compression chamber, with the suction opening at one end and emptying the other. As screws rotating in the space between one pair share of male and female grooves presented suction aperture. Suction gas flows into the lobe/groove space until the screws rotate enough for the bare end of this space to go beyond the suction aperture. On all length of a share/groove space is full of gas at a pressure of suction. As the rotation of screws continues male share reduces the amount of gas trapped in the women's groove, who, as contained in the plate at the discharge end of the compression chamber is compressed.

In the third phase rotation continues and the end share/groove space starts to discharge port, allowing hot gas flow in the pressure header.
Several share/groove spaces go through the suction and discharge openings in rapid succession and compressed gas flow smoothly and continuously, for all practical purposes.

The most common mechanism for the rotor to be driven from a two-pole electric motor. The female screw is then driven rotor, being separated from it by a film of oil. Besides, the woman rotor is driven instead of the rotor. Less popular method-ROM female screw through synchronization gear wheels of the screw, but it was very noisy in the beginning of the installation. Sliding between grid screws minimizes friction and wear high volumetric efficiency.

If both rotors are driven by the synchronization gear oil is not needed because there is no contact between the two screws. However, on the other arrangements oil is essential for lubrication, sealing and cooling. Oil takes a lot of heat compression and discharge temperatures of less than 88C. oil separator it is necessary in the discharge of hot gas and cooling is provided for oil or external heat exchanger or injection of liquid refrigerant in the compression process. Economizers are sometimes used to improve performance, secondary suction nozzle for gas integration between the main suction and discharge ports.

Capacity control is a sliding valve which, as it opens, allows suction gas escape to the suction side screws, without compression. This can give a smooth proportional control capacity of up to 10 percent of the design of the debt, but some machines are controlled by actions, 100%, 75%, 50%, 25% and 0%, whereas typical. Electric power consumption, as a rule, is proportional to the refrigeration debt of about 30 percent load, but in the future effectiveness of the poorer, about 20% of the energy absorbed by a 10 percent duty.

Vehicles, mostly with water cooling, but the cooling air is possible and the choice of cooling capacities from about 120 kW up to more than 2000 kW. As one screw, twin-screw can tolerate some liquid floodback.

Machine hermetic, semi-hermetic or open and motors in the sealed or - semi-hermetic compressors better cooled by suction gas. However, one machine is used for injection of gas this purpose, thus avoiding the necessity of separation of oil at the port of discharge. Sealed machine should not be used with high condensing temperature, to give heat pump or recover the heat. Instead, open the compressor should be used, where the driving motor is cooled in a traditional manner...

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