Refrigerating Systems. Screw compressors

Ironically, the screw was invented in 1878. However, commercial applications developed slowly because of its inability to meet strict tolerances with an existing production equipment time. Over the past 10 years, several producers presented Chillers with screw compressors and got away from the old piston technology. Screw compressor technology offers many benefits over piston types, including increased reliability and improved performance. In addition to these priorities, some remarkable features make the screw compressor compressor selection for future hmm developments and projects (Duncan, 1999).

Screw compressors are also positive displacement cooling system components. As one screw and twin-screw compressors are widely used in refrigeration. One of the screw compressor consists of one screw rotor (shaft)and a pair of gates rotors, which are then grid and together with the form of the case of pressurized volume, which is compressed. There are two different screw compressor designs. One-two spiral structures in which there are men's and women's rotor combined with each other (see Fig. 3.9a). The other is a single rotary screw design, in which the two gates of the rotors are placed on both sides of the main rotor compressor (see Fig. 3.9 billion).

Piston compressors until recently was carrying a load in applications requiring temperatures below -35 C. technology choice, mainly because the cascading system of cooling was the only choice. Screw compressors were developed specifically for use in applications -40 C or lower (down to -50C). Originally developed for large applications, this technology is now available in the chambers, requiring only a single 15 HP more powerful compressor. The development of this advanced screw-style cooling system provides the following advantages:

- better performance for HP,
- increase of reliability,
- reduction of costs,
- fewer moving parts
- less vibration, and
- less refrigerant loss.

Design and function, screw compressor has far fewer moving parts than with reciprocating style. Engineered without valves and bearings, parts are sharply reduced. This reduction of the parts is important because it significantly increases the reliability of compressors and increases the speed of the expected useful life.

Please note that the screw compressor technology significantly reduces the risk of refrigerant loss due to vibration reduction within the whole system. Any structuring within the refrigeration unit may cause the loss of refrigerant. With the acceleration of expenses on R-22, R-134a and R-507/404A, product loss is becoming a decisive factor operating.

A two-screw compressor consists of two spiral fluted rotors (containing a couple of mingling screws) and works as a pump (Fig. 3.10). Male screw is directly connected to an electric motor, and this leads to the compressor. With the lack of suction or discharge valves gas is drawn into the combustion chambers, between the gear teeth and cylinder wall and the spiral movement of the gears forces gas to move in rotor the shaft. Single-screw compressors are also available, and they consist of helical gear on the main rotor shaft and a pair of planet wheels, one on each side, to separate high and low pressure. Oil floods provides lubrication and limits of refrigerant leakage. These compressors are used mainly recover the heat and heat pumps.

Screw compressor (Fig. 3.10) has a rotor (with four blades), which manages the woman rotor (ravines) in stationary building with inlet port on one end and the output port to another. Rotating elements of open an empty input pipe fan, compressor, make the gas, and then seal the port. More speed decreases volume between the rotors and compresses the refrigerant gas. Gas is discharged to low-volume, high pressure at the outlet of the compressor through the outlet port. In General, the rotor is driven directly. On the other hand, the woman rotor rotates a rotor, or by gearing, or through direct contact with the rotor.

For industrial refrigeration applications such as process chillers, heat compact screw compressors provides the perfect solution. Built-in oil separator and oil stratum significantly reduces installation time, complexity, cost and space required. These compressors are available in sizes from 50140 PS, which are equipped with double system of power management and auto-economizer and can be used with common refrigerants R-134a, R-407C and R-22, R-404A, R-507A in special applications). Surgery with or without you can save money.

On Fig. 3.11 shows a cutaway view of a hermetic rotary screw compressor type normally used in small refrigeration systems, especially in the residential and commercial units.