The core working logic of a refrigeration compressor is to complete the “suction compression discharge” cycle of refrigerant vapor by consuming mechanical energy, promoting the circulation of refrigerant in the refrigeration system, and realizing the transfer of heat from low temperature environment to high temperature environment. Its working principle is essentially the compression cycle process in thermodynamics, and the circulation mode of different types of compressors may vary slightly, but the core principle is the same.
Taking the mainstream positive displacement compressor as an example, its working process is divided into four stages: the suction stage, the compressor increases the volume of the working chamber and reduces the internal pressure through the movement of the compression mechanism (such as piston, rotor). When the pressure is lower than the refrigerant vapor pressure in the evaporator, the low-temperature and low-pressure refrigerant vapor in the evaporator enters the working chamber through the suction valve to complete the suction; In the compression stage, the compression mechanism continues to move, and the volume of the working chamber gradually decreases. The refrigerant vapor entering the chamber is compressed, and the pressure and temperature rise synchronously. During this process, the mechanical energy of the motor is converted into the internal energy of the refrigerant; During the exhaust phase, when the pressure of the refrigerant vapor rises above the pressure inside the condenser, the exhaust valve opens and the high-temperature and high-pressure refrigerant vapor is discharged into the condenser, completing the exhaust process; In the expansion stage, after the exhaust is completed, the compression mechanism moves in the opposite direction, and the working chamber volume slightly increases. The internal pressure briefly decreases to prepare for the next intake. Some compressors reduce gas residue and improve compression efficiency by setting clearance volume.
The working principle of a centrifugal refrigeration compressor is different from that of a volumetric compressor. It generates centrifugal force through a high-speed rotating impeller, which sucks refrigerant vapor into the impeller. The impeller drives the refrigerant to rotate at high speed, giving it kinetic energy. Then, the refrigerant enters the diffuser, where the flow rate decreases and the kinetic energy is converted into pressure energy, achieving steam compression. Afterwards, the high-temperature and high-pressure refrigerant vapor is discharged to the condenser through the volute shell. The compression process of a centrifugal compressor is continuous, without obvious suction, compression, and exhaust sections, making it suitable for refrigeration scenarios with high flow rates and low pressure ratios.
Regardless of the type, the operation of a refrigeration compressor must comply with the first law of thermodynamics. During the compression process, heat is generated, and some of the heat is dissipated through the cooling mechanism to avoid refrigerant decomposition and lubricating oil carbonization caused by high exhaust temperatures, which can affect the normal operation of the refrigeration system. At the same time, the compression ratio of the compressor (the ratio of exhaust pressure to suction pressure) is a key parameter. If the compression ratio is too large or too small, it will affect the refrigeration efficiency and needs to be accurately matched according to the application conditions.
