Basic knowledge of refrigeration compressor (technology sharing)

Basic knowledge of refrigeration compressor (technology sharing) Compressor, a driven fluid machine that promotes low-pressure gas to high-pressure gas. It is the heart of the refrigeration system. It sucks in low-temperature and low-pressure refrigerant gas from the suction pipe, drives the piston to compress it through the operation of the motor, and discharges the high-temperature and high-pressure refrigerant gas to the exhaust pipe to provide power for the refrigeration cycle. Compression → condensation (heat release) → expansion → evaporation (heat absorption) refrigeration cycle. 　　 Linear compressor adopts magnetic levitation principle and spiral ring hydrodynamic structure to compress gas and provide power for refrigeration. 　　 Compressors are divided into piston compressors, screw compressors, centrifugal compressors, linear compressors, etc. Piston compressors are generally composed of housing, motor, cylinder, piston, control equipment (starter and thermal protector) and cooling system. There are two cooling methods: oil cooling and natural cooling. The linear compressor has no shaft, no cylinder, no shaft, seal and heat dissipation structure. 　　Compressors of general household refrigerators and air conditioners use single-phase alternating current as their power source, and their structural principles are basically the same. The refrigerant used in the two is different. 　　The compressor is produced in an assembly line. Cylinder blocks, pistons (rotating shafts), valve plates, connecting rods, crankshafts, end covers and other parts are manufactured in the machining workshop (including casting); rotors and stators are assembled in the motor workshop; shells are manufactured in the press workshop. Then it is assembled, welded, cleaned and dried in the assembly workshop, and finally packaged and shipped after inspection. 　　Most compressor manufacturers do not produce starters and thermal protectors, but purchase them from the market as needed. Representative compressor companies include: Meizhi, Lingda, Mitsubishi, Embraco, etc. 　　 There are five types of compressors used in the refrigeration and air-conditioning industry: reciprocating, screw, rotary, scroll and centrifugal. The reciprocating compressor is the most widely used compressor in small and medium-sized commercial refrigeration systems. Screw compressors are mainly used in large commercial and industrial systems. Rotary compressors and scroll compressors are mainly used in household and small-capacity commercial air-conditioning devices, while centrifugal compressors are widely used in air-conditioning systems in large buildings. 　　Various reciprocating compressors are generally classified according to the compressor housing form and the setting mode of the drive mechanism. According to the shell type, there are open and closed semi-hermetic compressors. Closed type means that the entire compressor is arranged in a shell. 　　 method When the compressor is started, the current of the motor will be 5-6 times higher than the rated current, which will not only affect the service life of the motor but also consume more power. The system will have a certain margin in the motor selection during the design. The speed of the motor is fixed, but in actual use, it sometimes needs to run at a lower or higher speed, so it is very necessary to carry out frequency conversion transformation. The frequency converter can realize the soft start of the motor, achieve the purpose of energy saving and speed regulation by changing the input voltage frequency of the equipment, and can provide the equipment with protection functions such as overcurrent, overvoltage and overload. The domestic inverter manufacturers that have done better include Sanjing and INVT. For more energy-saving transformation methods of screw air compressors, please refer to the book "Questions and Answers on Operation and Maintenance of Screw Air Compressors" by Electric Power Press 　　 type 　　 compressor can be divided into positive displacement compressor and speed compressor according to its principle. The volume type is divided into: reciprocating compressor, rotary compressor; speed type compressor is divided into: axial compressor, centrifugal compressor and mixed flow compressor. 　　 Nowadays, household refrigerators and air conditioner compressors are both positive displacement, which can be divided into reciprocating and rotary. Reciprocating compressors use piston, crank, connecting rod mechanism or piston, crank, slide tube mechanism, and rotary compressors are mostly rolling rotor compressors. In commercial air conditioners, most of them are centrifugal, scroll, and screw. 　　 can be divided into low back pressure type, medium back pressure type and high back pressure type according to the scope of application. Low back pressure type (evaporating temperature -35 ～ -15 ℃), generally used in household refrigerators, food freezers, etc. Medium back pressure type (evaporating temperature -20 ～ 0 ℃), generally used in cold drink cabinets, milk refrigerators, etc. High back pressure type (evaporating temperature -5 ~ 15 ℃), generally used in room air conditioners, dehumidifiers, heat pumps, etc. 　　The compressor specifications are divided according to the input power. Generally, the difference between each specification is about 50W. In addition, there are also divided by cylinder volume. 　　Main performance 　　 Input and output power, coefficient of performance, cooling capacity, starting current, running current, rated voltage, frequency, cylinder volume, noise, etc. Measure the performance of a compressor, mainly from the comparison of weight, efficiency and noise. 　　According to Chinese standards, its safety performance inspection is carried out in accordance with GB4706.17-2004. The main items are electrical strength, leakage current, locked rotor, and overload operation test. 　　The performance inspection of the air conditioner compressor is carried out in accordance with the regulations in GB5773-2004. In addition, when there are major changes that may affect product performance during product finalization and production, continuous production for one year or more than one year after re-production, and when there is a big difference between the factory inspection result and the type test, the type test must be carried out. . 　　Packaging, storage and transportation 　　 The packaging and transportation of the compressor can be handled according to the contract. Compressors imported in large quantities are generally packed in cartons and then shipped in containers. The compressor should be firmly fixed in the packing box, and have moisture-proof and shock-proof measures. Do not put it upside down during storage and transportation, and store it in a well-ventilated warehouse. The relative humidity should not exceed 80% and there should be no corrosive gases. Precautions 　　 Only when the compressor is in use, the sealing rubber plug is allowed to be pulled out. If the plug is detached or loosened during storage and transportation, it should be checked and treated in time before saving. Refrigerator compressors and air conditioner compressors must be CCC certified before they can be sold. 　　Importing country 　　In the case of insufficient supply of domestic compressors, China still needs to import a moderate amount every year. The main trading countries are Germany, the United States, Italy, Japan, Denmark, Brazil, South Korea, etc. The equipment transformation has greatly improved the quality and output of domestic compressors.