What are the requirements for refrigeration equipment for fully synthetic refrigeration oil?
Refrigeration equipment has different choices for refrigeration oils due to the use and refrigerant. The requirements for refrigeration oil are as follows:
(1) Viscosity An important parameter in the characteristics of the oil viscosity of the refrigerating oil. Different refrigerants should be used to select different refrigerating oils. If the viscosity of the frozen oil is too large, the mechanical friction power, friction heat and starting torque will increase. On the other hand, if the viscosity is too small, the desired oil film cannot be formed between the moving parts, so that the desired lubrication and cooling effect cannot be achieved.
(2) Cloud point The cloud point of the refrigerating oil refers to the temperature at which the paraffin is precipitated in the refrigerating oil when the temperature is lowered to a certain value to make the lubricating oil turbid. The cloud point of the refrigeration oil used in the refrigeration equipment should be lower than the evaporation temperature of the refrigerant, otherwise it will cause the throttle valve to block or affect the heat transfer performance.
(3) Freezing point The temperature at which the frozen oil is cooled to the stopped flow under the experimental conditions is called the freezing point. The freezing point of the refrigeration oil used in the refrigeration equipment should be as low as possible (such as the compressor of R22, the refrigeration oil should be below -55 °C), otherwise it will affect the flow of the refrigerant and increase the flow resistance, resulting in poor heat transfer.
(4) Flash point The flash point of the frozen oil refers to the lowest temperature at which the lubricating oil is heated to the point where it is in contact with the flame. The flash point of the refrigeration oil used in the refrigeration equipment must be 15 to 30 °C higher than the exhaust gas temperature to avoid burning and coking of the lubricating oil.
(5) Others such as chemical stability and oxidation resistance, moisture and mechanical impurities, and insulation properties.