Analysis of the application, advantages and disadvantages of the five major refrigeration compressors Semi-sealed piston refrigeration compressor At present, semi-hermetic piston compressors are mostly used in the cold storage and freezing and refrigeration markets (commercial refrigeration and air conditioning are also useful, but they are relatively less used now). The semi-enclosed piston cold storage compressor is generally driven by a four-pole motor, and its rated power is generally between 60-600KW. The number of cylinders is 2-8, up to 12. advantage: 1. Simple structure and mature manufacturing technology; 2. The requirements for processing materials and processing technology are relatively low; 3. It is easy to achieve high compression ratio, so it is adaptable and can be used in a very wide pressure range; 4.The device system is relatively simple and can be applied to a wide pressure range and cooling capacity requirements.
Disadvantages: 1. Large and heavy; 2. With greater noise and vibration; 3. It is difficult to achieve high speed; 4. Large gas pulsation; 5. There are many vulnerable parts, and they are afraid of liquid shock. 2 Rotor refrigeration compressor: Rotor refrigeration compressors are fully enclosed and are generally used in household air conditioners or small refrigeration equipment. The refrigeration capacity of the compressor is not high, ranging from 3KW to 15KW. advantage: 1. Simple structure, small size and light weight. Compact size; 2. No suction valve, high speed, low vibration, stable operation; 3.Suitable for variable speed operation, the speed ratio can reach 10:1;
Disadvantages: 1. The system requires high cleanliness and processing accuracy; 2. The leakage, friction and wear between the sliding vane and the cylinder wall are relatively large, and the performance is significantly reduced; 3. The unevenness of the rotation speed of the single-rotor compressor at low rotation speed increases; 3 Scroll refrigeration compressor: Scroll refrigeration compressors are currently mainly based on a fully enclosed structure, mainly used in air conditioning (heat pump), heat pump hot water, refrigeration and other fields. The supporting downstream products are: household air conditioners, multi-line, modular machines, small water and ground source heat pumps, etc. At present, a single manufacturer of scroll refrigeration compressors can achieve 20~30HP. advantage: 1. There is no reciprocating motion mechanism, so the structure is simple, small in size, light in weight, few parts (especially few wearing parts), and high reliability; 2. The torque change is small, the balance is high, the vibration is small, the operation is stable, and the vibration of the whole machine is small; 3. It has high efficiency and variable frequency speed regulation technology within its applicable cooling capacity range; 4. The scroll compressor has no clearance volume and can maintain high volumetric efficiency operation 4.Low noise, good stability, high safety, relatively not easy to hit by liquid.
Disadvantages: 1. High precision requirements, shape and position tolerances are in the micron level; 2. No exhaust valve, poor performance under variable working conditions; 3. It is not easy to implement external cooling in the working cavity, and the heat in the compression process is difficult to discharge, so it can only compress gas with a small adiabatic index or internal cooling; 4. It is difficult to realize the large displacement scroll compressor. Limited by the tooth height, the displacement is large and the diameter is large, and the unbalanced rotating mass increases. 4 Screw refrigeration compressor: Screw compressors can be divided into non-single screw compressors and twin screw compressors. It is now widely used in refrigeration equipment such as refrigeration, HVAC, and chemical processes. The input power range has been developed to 8-1000KW, and its research and development fields are very extensive, with great potential for performance optimization. advantage: 1. Few parts, less wearing parts, high reliability, stable and safe operation, low vibration; 2. The efficiency of part load is high, liquid hammer is not easy to occur, and it is not sensitive to liquid hammer; 3. It has the characteristics of forced gas transmission and has strong adaptability to working conditions; 4. Stepless adjustment is possible. Disadvantages: 1. The price is high, and the machining accuracy of body parts is high; 2. High noise during compressor operation; 3. The screw compressor can only be used in the middle and low pressure range, not in the high pressure occasions; 4. Due to the large fuel injection volume and the complicated oil treatment system, there are many auxiliary equipment for the unit. 5 Centrifugal refrigeration compressor: The centrifugal compressor has a large refrigeration capacity and is suitable for large-scale central air-conditioning systems and petrochemical industries. It is mostly used for air conditioning adjustment or refrigeration requirements in large buildings. advantage: 1. In the case of the same cooling capacity, especially when the capacity is large, compared with the reciprocating compressor unit, the huge oil separation device is omitted, the weight and size of the unit are smaller, and the footprint is small; 2. The centrifugal compressor has a simple and compact structure, few moving parts, reliable work, durable, low operating cost, easy to achieve multi-stage compression and multiple evaporation temperatures, and easy to achieve intermediate cooling; 3. There is very little lubricating oil mixed in the centrifugal unit, which has little influence on the heat transfer effect of the heat exchanger, and the unit has a higher efficiency; 5.Large gas delivery, high speed, uniform gas supply, eliminating the shortcomings of gas carrying oil;
Disadvantages: 1. It is not suitable for small flow occasions, where the single-stage pressure ratio is low. In order to obtain a higher pressure ratio, multi-stage impellers are required, and speed-increasing gears are generally used; 2. Surge is an inherent shortcoming of centrifugal compressors, the working conditions of the same unit cannot be changed greatly, and the scope of application is relatively narrow; 3. The centrifugal compressor can only obtain the highest efficiency when working under the design conditions, and it is easy to surge 4. Poor operation adaptability, high gas flow rate, high friction resistance and low efficiency; 5. The compression outlet temperature is relatively high, and the heat exchange area is easily affected by changes in the temperature, pressure, and composition of the compression medium.
