Principles And Advantages And Disadvantages Of Cold Storage Screw Compressor Refrigeration Unit

First, the working principle of screw compressor refrigeration unit
Screw refrigeration compressor is a new type of high-speed compressor. The principle of increasing gas pressure is the same as that of piston compressor, which belongs to volumetric compression. At present, twin screw compressors are generally used. Twin screw compressors use two mutually intermeshing screws to make relative rotational movements to compress the gas.

With the rapid development of the refrigeration industry and the improvement of processing methods, screw compressor refrigeration units have developed greatly. The cold storage is gradually becoming larger, the types of units are increasing, the scope of use is expanding, and it is expanding to different application areas.

Driven by the motor, the driving rotor rotates with the motor, and at this time, the driven rotor that is engaged also follows the opposite direction. In the rotor movement, when a pair of meshing grooves of the driving rotor and the driven rotor communicate with the suction duct, sufficient suction is performed. When the rotor continues to rotate, the pair of suction grooves leaves the suction orifice on the suction end face, and the gas in the tooth groove enclosed by the suction and exhaust end seats is isolated from the outside of the casing and begins to be compressed.

The driving and driven rotors continue to rotate, and the tooth peaks of the driving rotor continuously fill the tooth valleys of the driven rotor. Similarly, the tooth peaks of the driven rotor also continuously fill the tooth valleys of the corresponding driving rotor. As a result of the mutual filling, the groove volumes of the respective rotors are gradually reduced, and the gas in the grooves is gradually compressed. When the gas pressure reaches the specified value, the rotor is turned to a position where the groove communicates with the exhaust port to discharge the gas. Such continuous operation, the refrigerant is continuously compressed and discharged from the screw compressor refrigeration unit.

Screw refrigeration compressors inject a large amount of oil during the compression process, which can take away the heat generated during the compression process. At the same time, the oil film is used to seal the gap between the female and male rotors and the gap between the rotor and the cylinder, so that internal leakage losses are reduced.

Advantages and disadvantages of screw compressor refrigeration unit

1. Main advantages
(1) Easy management
The screw compressor refrigeration unit has no suction and exhaust valves, pistons, piston rings, cylinder liners and other fragile parts, which is convenient for maintenance and repair. Smooth and reliable operation, easy to realize long-distance operation and automation.

(2) High speed and good economic performance.
Screw compressors are rotary machines. Because there are no suction and exhaust valves, the speed can be increased. Usually the speed is 1500-3000 / min, which is generally higher than the speed of piston compressors, thus improving the economic indicators.

(3) Small size and light weight.
Due to the high speed, when the exhaust volume is the same, the machine is small in size, compact in structure, light in weight, low in metal consumption, and small in area.

(4) The foundation is small.
Since the screw compressor refrigeration unit does not have the mass inertia force of the piston compressor and the dynamic balance performance is good, the foundation can be made small.

(5) Strong adaptability to operation.
Can be applied to a variety of refrigerants, high volume efficiency. Good performance even at low evaporation temperatures and high compression ratios. Because there is no clearance volume, the volumetric efficiency is much higher than the piston type.

(6) The exhaust temperature is low.
With oil injection cooling, the exhaust temperature is lower than the reciprocating type, so single-stage compression can still be used at higher compression ratios. When the evaporation temperature is -40 ° C, the discharge temperature is less than or equal to 90 ° C, which is beneficial to the operation of the machine.

(7) Continuous stepless adjustment.
Since the most widely used current is the use of slide valves for energy adjustment, the refrigeration capacity can be adjusted steplessly within the energy range of 10% to 100%, achieving continuous stepless adjustment.

(8) There is no danger of liquid strike.
Due to the structural characteristics, the screw compressor is not sensitive to the wet stroke. It can allow wet vapor or a small amount of liquid refrigerant to enter the body without the risk of liquid strike.

2. The main disadvantages
(1) Rotor processing is difficult.
The rotor requires high machining accuracy and is difficult to process, requiring special equipment.

(2) The auxiliary equipment is huge.
For screw compressor refrigeration unit, in order to separate the lubricating oil in the exhaust gas, an oil separator and an oil return device with large volume, complicated structure and high efficiency are required.

(3) The noise is large.
Because the rotor cogging passes through the suction and exhaust orifices at high speed periodically, and leaks through the gap, the noise is relatively large. Generally, if all screw-type refrigeration compression is set in the machine room, the machine room should not be close to the main warehouse or other workshops. It is better to leave it separately from other buildings.

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