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1. Semi-sleeve piston refrigeration compressors: Among various types of refrigeration compressors, piston compressors are the earliest type to have been developed and remain widely used to this day. For example, semi-hermetic piston refrigeration compressors are widely used in freezing and refrigeration equipment. Common manufacturers include Emerson, Bitzer, Sanyo, Dulink, and other compressor brands. Features of semi-hermetic piston refrigeration compressors: they offer a wide range of pressure levels and cooling capacities, have low requirements regarding materials, are technically mature, and have a relatively simple compressor system; however, they are very sensitive to liquid slugging. The common faults of semi-hermetic piston refrigeration compressors fall into two categories: mechanical faults and electrical faults. Common mechanical failures include wear or damage to the connecting rods, crankshaft, valve plates, and valves ； Electrical faults are commonly seen in the form of short circuits, open circuits, and burns in motor windings. 2. Twin-rotor refrigeration compressors: Twin-rotor compressors are now widely used in household appliances. The export volume of such compressors has been on the rise year after year; during the ten-year period from the 2009 to 2019 cooling seasons, the compound annual growth rate was 12.8%. Currently, many air conditioning units with a capacity of less than 7 horsepower opt for twin-rotor compressors. Features of rotary compressor: few components and simple structure. Few vulnerable parts; reliable operation. There is no suction valve plate, the clearance volume is small, the gas transfer coefficient is high, high precision in manufacturing is required, the sealing performance is poor, and there are significant leakage losses. Previously, a friend asked about the advantages of vortex compressors and twin-rotor compressors when compared to each other. The advantages of twin-rotor compressors are: good energy efficiency at low frequencies; however, their energy efficiency at high frequencies is inferior to that of scroll compressors. They generate more noise, vibration, and wear compared to scroll compressors, have a shorter lifespan, and it is difficult to create compressors with large displacement volumes using this design. The advantages of vortex compressors are: a moderate energy efficiency at low frequencies, better energy efficiency at high frequencies compared to vortex compressors, low noise and vibration levels, minimal wear, a long service life, and the ability to handle large displacement volumes. 3. Vortex refrigeration compressors: A vortex compressor is mainly composed of a moving disk (vortex rotor), a stationary disk (vortex stator), a bracket, a cross coupling ring, a back pressure chamber, and an eccentric shaft. It can be divided into low-pressure chamber compression and high-pressure chamber types. The low-pressure chamber compressor features a low temperature throughout its entire housing, with low pressure inside the housing cavity (except at the exhaust port and the exhaust chamber) ； The high-pressure chamber compressor features a whole housing that is hot, with high pressure throughout the chamber (except at the suction port and suction chamber). Features of vortex compressors: smooth operation, low vibration, a quiet working environment, very few vulnerable components, stable performance, low noise level, long service life, and a high EER value. They are used in both refrigeration and air conditioning systems. 4. Screw refrigeration compressors: Screw refrigeration compressors are mainly composed of a casing, rotors, bearings, shaft seals, balance pistons, energy regulation devices, etc. A screw refrigeration compressor features two screws with spiral grooves that rotate while meshing with each other, causing changes in the volume between the teeth and thus enabling the processes of suction and compression. The cooling capacity can be adjusted continuously from 10% to 100%. Screw refrigeration compressors are now widely used in freezing and refrigeration as well as HVAC equipment. Features of screw refrigeration compressors: The rotors and bearings have high strength and wear resistance ； The displacement is hardly affected by the exhaust pressure ； Maintains high efficiency over a wide range of operating conditions ； It enables stepless energy adjustment and is insensitive to the incoming fluid. Someone previously asked in the Refrigeration Encyclopedia technical group whether screw compressors are vulnerable to liquid slugging, and many people replied that they are not. In fact, screw compressors are also vulnerable to liquid slugging; however, they are less sensitive to a small amount of backflow. Yet, a large amount of backflow can still cause compressor failures, and this is something that needs to be taken into account. 5. Centrifugal refrigeration compressors: Centrifugal refrigeration compressors belong to the speed-type compressors and are mechanical devices that utilize rotating impellers. It relies on a high-speed rotating blade wheel to do work on the gas in order to increase its pressure. Refrigeration compressors with a single-unit capacity of over 1200 kW almost all use centrifugal refrigeration compressors; centrifugal compressors are generally used in large and very large air conditioning systems. Features of centrifugal refrigeration compressors: good dynamic balance and low vibration ； Few wear-prone components; long continuous operating cycle ； Easy to achieve multi-stage compression and throttling, allowing for various evaporation temperatures ； Capable of economical stepless adjustment ； When the cooling capacity is low, the efficiency is lower ； Prone to surge,