What is the difference between screw refrigeration compressor and piston refrigeration compressor?

Distinguishing from Types

Screw refrigeration compressor and piston refrigeration compressor belong to volumetric compressor, and screw refrigeration compressor is a new type of high speed refrigeration compressor.

Principle distinction

According to the principle of compressed gas, both compressors have the common ground that the compressed gas is compressed by the change of volume; the difference is that the two compressors have different ways to realize the change of working volume. The piston refrigeration compressor changes the working volume of the cylinder by means of the movement of the crankshaft connecting rod mechanism, while the screw refrigeration compressor changes the working volume by means of the rotation movement of the rotor directly connected to the shaft.

Distinguishing from the overall structure

Screw refrigeration compressor has no cylinder, piston, piston ring, cylinder liner and other vulnerable parts required by piston refrigeration compressor. The machine is compact in structure, small in size, light in weight, no clearance volume, and there is no danger of liquid shock when a small amount of liquid enters the machine. The valve can be used for stepless energy regulation of 10%-99%. It has wide application range, stable and reliable operation, long maintenance period and (2-5)*104h trouble-free operation time. Because the use of lubricating oil improves the cooling and sealing performance of the machine and reduces the exhaust temperature, even if the evaporation temperature is low (-40 C) and the compression ratio is high (about 25), it can still operate in a single stage, that is to say, it can replace the two-stage compression cycle in a range. However, screw refrigeration compressor requires high precision in processing and assembly, is not suitable for off-design operation, and has a greater noise. In general, it needs to install muffler and sound insulation equipment. When refrigerating and compressing, it needs to spray lubricating oil. Therefore, it needs many auxiliary equipment such as oil pump, oil cooler and oil recoverer.

In recent years, a screw compressor with adjustable volume ratio has been developed. The adjustable range is 2.6-5, which further improves the performance of the screw compressor. Recently, a new type of semi-closed screw machine has been developed in China, which uses 5:6 asymmetric new tooth profile to greatly improve the volumetric efficiency. The operation economy, reliability and service life of the new screw refrigeration compressor have exceeded that of the piston refrigeration compressor. Therefore, full attention should be paid to the design and selection of refrigeration units.