How to choose refrigeration oil for refrigeration compressor and unit

How to choose refrigeration oil for refrigeration compressor and unit The lubricating oil of the refrigerator is different from other mechanical equipment. Due to the different use occasions and refrigerants, the choice of lubricating oil for the refrigerator is also different. The requirements for refrigeration oil are as follows:    1. Viscosity: The viscosity of the lubricating oil is an important parameter in the characteristics of the oil. Different refrigerants should be used to select different refrigeration oils. Also. The viscosity of lubricating oil is also related to the temperature of the freezer. As the temperature increases, the viscosity of the oil decreases. Excessive viscosity of the lubricating oil in the refrigeration equipment will increase the mechanical friction power, friction heat and starting torque. If the viscosity is too small, the required oil film will not be formed between the moving parts, and the proper lubrication and cooling cannot be achieved effect.    2. Cloud point: The cloud point of lubricating oil refers to the temperature at which paraffin wax starts to precipitate in the lubricating oil when the temperature drops to a certain value, making the lubricating oil cloudy. The cloud point of the lubricating oil used in refrigeration equipment should be lower than the evaporation temperature of the refrigerant, otherwise when the lubricating oil precipitates paraffin, it will accumulate at the throttle valve, block the throttle valve, or may accumulate on the heat transfer surface of the evaporator, affecting Heat transfer performance.    3. Freezing point: The temperature at which the lubricating oil is cooled to stop flowing under the experimental conditions is called the freezing point. In refrigeration systems, heat exchange equipment and pipes usually work at low temperatures, and oil film layers appear more or less on the walls of the pipes. If the freezing point of oil is too high, it will affect the flow of refrigerant, increase the flow resistance, and affect Heat transfer effect. Generally speaking, for freezing equipment, the freezing point should be as low as possible. For example, for R-22 compressors, the freezing oil should be below -55℃. If used in low-temperature devices, the freezing point should be lower.    4. Flash point: This refers to the minimum temperature at which the lubricating oil is heated to the point where its steam comes into contact with the flame. The flash point of the lubricating oil used in refrigeration equipment must be higher than the exhaust temperature by 15 to 30 ℃, so as not to cause combustion and coking of the lubricating oil. Usually R-12 and R-22 lubricating oils have a flash point above 160°C.    5. Chemical stability and anti-oxidation: the pure lubricating oil has stable chemical composition, does not oxidize, and will not corrode metals. However, when the lubricating oil contains refrigerant or moisture, it will cause corrosion. After oxidation of the lubricating oil, it will generate acid and corrode the metal. When the lubricating oil is at high temperature, coke will appear. If this substance is attached to the valve disc, it will affect the normal operation of the valve disc, and at the same time it will cause the filter and the throttle valve to block. Therefore, it is necessary to select refrigerator lubricants with good chemical stability and oxidation resistance.    6. Moisture and mechanical impurities: If the lubricating oil contains moisture, it will aggravate the chemical changes of the oil, make the oil deteriorate, and cause corrosion to the metal. At the same time, it will cause "ice blockage" at the throttle or expansion valve. The lubricating oil contains mechanical impurities, which will aggravate the wear of the friction surface of the moving parts, and quickly block the filter and the throttle valve or expansion valve, so the refrigerator lubricating oil should not contain mechanical impurities.    7. Insulation performance: In semi-closed and fully enclosed refrigerators, the frozen lubricating oil and refrigerant are in direct contact with the windings and terminals of the motor. Therefore, the lubricating oil is required to have good insulating properties and high breakdown voltage. Pure lubricating oil has better insulation performance, but when it contains moisture, impurities and dust, its insulation performance will decline. Generally, the refrigeration oil of a refrigerator requires a breakdown voltage of more than 2.5KV. 8. Due to the different characteristics of various refrigerants, the operating temperature of the refrigeration system differs greatly, and the refrigerator oil can generally be selected in this way: the refrigeration equipment at low speed and low temperature can choose lubrication with low viscosity and low freezing point Oil; and refrigeration equipment under high-speed or air-conditioning working conditions should use lubricating oil with high viscosity and high freezing point. Refrigerating machine oil is divided into five viscosity grades of N15, N22, N32, N46 and N68 according to the kinematic viscosity at 40℃. The choice of refrigeration oil mainly depends on the type of refrigerant, compressor type, operating conditions (evaporation temperature, condensation temperature Etc.), generally selected according to the specified requirements of the compressor.

Recent related posts

Customers frequently viewed

Submitted Successfully
Submission Failed