Introduction of Refrigerant Oil Related Knowledge

1. Classification of refrigerant oil  

One is traditional mineral oil;  The other is a synthetic polyol ester oil such as PO, often called polyester oil is also a synthetic poly (b) diol lubricating oil, their Chinese name is not very unified.  POE oil can be used not only in HFC refrigerant system, but also in hydrocarbon refrigerant.  PAG oil can be used in HFCS, hydrocarbons and ammonia systems as refrigerants.  

2. Main functions of refrigerating oil  

Reduce friction work, friction heat and wear;  

Fill the sealing part with oil to ensure sealing performance and prevent refrigerant leakage;  

The movement of oil takes away the dust generated by metal friction and plays a role in cleaning the friction surface.  

Provide hydraulic power for unloading mechanism  

3. Performance requirements of refrigerant oil  

Appropriate viscosity: the viscosity of refrigerant oil in addition to ensure that the friction surface of the moving parts has good lubricity, but also to take away part of the heat from the refrigerator, and play a sealing role.  If the refrigerant used by the refrigerator is mutually soluble to the refrigerant oil, it should be considered to use the oil with greater viscosity, in order to overcome the influence of lubricating oil diluted by the refrigerant.  

Small volatility, high flash point: the more volatile refrigerant oil, with the refrigerant circulation of the oil is also more, so the refrigerant oil distillate range is required to narrow the better, flash point should also be higher than the refrigerator exhaust temperature of 25 ~ 30℃.  

Good chemical stability and thermal oxidation stability: the final compression temperature of the refrigerator can reach 130℃ ~ 160℃. At this temperature, the refrigerant oil will be heated and constantly decompose and deteriorate, resulting in carbon deposition and refrigerator failure and wear.  And the decomposition products of oil will react with the refrigerant, so that the refrigeration effect is bad, and the acid generated will strongly corrodes the refrigerator components.  

No water and impurities: because water freezes in the evaporator will affect the heating efficiency, and contact with refrigerant will accelerate the decomposition of refrigerant and corrosion of equipment, so the refrigerant oil can not contain water and impurities.  

Other: Refrigerant oil should also have good foam resistance, rubber, enameled wire and other materials do not dissolve, do not expand.  It should have good electrical insulation when used in enclosed refrigerator.  

4. Factors that should be considered when choosing refrigerant oil  

Viscosity: the higher the speed of the compressor, the greater the viscosity of the refrigerant oil.  

Thermal stability: Thermal stability is generally measured by flash point of refrigerant oil.  Flash point refers to the temperature at which the steam of refrigerant oil flashes when it encounters fire.  Flash point of refrigerant oil must be higher than the exhaust temperature of the compressor, such as R717, R22 compressor using refrigerant oil flash point should be above 160℃.  

Fluidity: the refrigerant oil should have good fluidity at low temperature. In the evaporator, due to low temperature, the viscosity of the oil increases, the fluidity becomes worse. When the refrigerant oil stops flowing at a certain temperature, the temperature at this time is called the freezing point of the oil.  The freezing point of refrigerating machine oil is required to be low, especially the freezing point of oil in low temperature refrigerating machine is very important.  

Solubility: all kinds of refrigerant and refrigerant oil are not the same, roughly divided into three categories: one is mutually insoluble, one is mutually infinite dissolution, and another is between the two.  

Turbidity point: The temperature at which the refrigerant oil starts to precipitate paraffin (oil becomes cloudy) is called the turbidity point. When there is refrigerant, the turbidity point of the refrigerant oil will decrease.  

5. The main reason for deterioration of refrigerated oil  

Mixed with water: because of the infiltration of air in the refrigeration system, the water in the air is mixed with the refrigerant oil after contact;  More water content in refrigerant will also make water mixed with refrigerant oil.  After the refrigerant oil is mixed with water, the viscosity decreases, causing corrosion to the metal.  In freon refrigeration system, can also cause "ice jam" phenomenon;  

Oxidation: Refrigerated oil in the use process, when the exhaust temperature of the compressor is higher, it may cause oxidative deterioration, especially refrigerated oil with poor chemical stability, is more prone to deterioration. After a period of time, residue will be formed in refrigerated oil, so that the lubrication of bearings and other places becomes bad.  Organic fillers, mechanical impurities and other mixed into the refrigerant oil will also accelerate its aging or oxidation;  

Refrigerant oil mixing: when several different grades of refrigerant oil are mixed, the viscosity of refrigerant oil will be reduced, and even the formation of oil film will be destroyed, and the bearing will be damaged;  If two kinds of refrigerant oil, containing different properties of antioxidant additives, when mixed together, it is possible to produce chemical changes, the formation of sediment, so that the lubrication of the compressor is affected, so pay attention to the use.