The Impact of Different Types of Refrigeration Machine Oil on the Performance of Piston-Type Refrigeration Compressors

Different types of refrigeration oil affect the performance of reciprocating refrigeration compressors in terms of lubrication, sealing, heat transfer, operational stability, and service life. Mineral oil features good compatibility with traditional refrigerants such as R22 and forms tough oil films. It can effectively lubricate pistons, valve plates, crankshaft connecting rods, and other components, and delivers excellent sealing performance to reduce internal leakage of the unit. Nevertheless, it has poor low-temperature fluidity, tends to wax, and suffers poor oil supply under low-temperature conditions. It is also incompatible with new environmentally friendly refrigerants including R134a and R410A. POE synthetic oil has great miscibility with HFC refrigerants and outstanding low-temperature fluidity, ensuring stable oil supply in low-temperature environments and reducing unit start-stop failures. It also boasts superior chemical stability with less carbon deposition, which slows down component aging. However, its load-bearing capacity of oil film is inferior to mineral oil, resulting in slightly weaker sealing performance. In addition, it is highly hygroscopic; moisture ingress will easily cause system ice blockage and component corrosion. PAG synthetic oil has a high viscosity index and excellent high-temperature oxidation resistance, making it suitable for reciprocating compressors used in high-temperature working conditions and heat pump units. Its drawbacks include limited compatibility with some refrigerants and a relatively high price. Improper selection of refrigeration oil will aggravate mechanical wear, increase vibration and noise, reduce refrigeration efficiency, and greatly shorten the service life of the compressor.