There is a close correlation between the oil separator efficiency of low temperature chiller and the lubrication reliability of the compressor. The main function of the oil separator is to separate the lubricating oil carried in the exhaust of the compressor, preventing it from entering the condenser and evaporator, thereby reducing the efficiency of the heat exchanger and affecting the normal operation of the compressor. Therefore, the efficiency of the oil separator directly affects the lubrication reliability of the compressor.

The influence of the efficiency of the oil separator on the reliability of compressor lubrication

The higher the efficiency of the oil separator is, the more lubricating oil is separated from the compressor exhaust, and the more lubricating oil can be returned to the compressor. This helps maintain a stable supply of lubricating oil inside the compressor, thereby ensuring the normal lubrication and cooling of the compressor. For instance, it was mentioned that when using high-viscosity refrigeration oil, due to its increased viscosity at low temperatures, it is prone to adhere to the inner wall of the evaporator to form an oil film, which affects the heat exchange effect. By installing a secondary oil separator, the amount of oil entering the evaporator can be reduced to the minimum, thereby improving the refrigeration efficiency and enhancing the reliability of the system operation.

It is pointed out that the oil separation efficiency of the centrifugal oil separator can reach over 99%, and at the same time, it can also reduce the vibration and noise of the compressor. This highly efficient oil separation not only helps to reduce the entry of lubricating oil into the system, but also enhances the operational stability of the compressor.

2. The relationship between the efficiency of the oil separator and the return oil of the system

The efficiency of the oil separator also directly affects the oil return capacity of the system. If the oil separator is inefficient and fails to effectively separate the lubricating oil, the oil may enter the evaporator, forming an oil film that hinders gas flow and reduces volumetric efficiency. Research shows that when the circulation volume of lubricating oil exceeds 3%, the heat exchange capacity will deteriorate and the pressure loss will increase. When it reaches 5%, the cooling capacity decays by more than 10%, increasing power consumption and reducing the system's cooling capacity.

To reduce the amount of refrigeration oil entering the heat exchanger and ensure the stable and safe operation of the compressor, a return oil system is usually installed in the refrigeration unit, which includes components such as high-performance oil separators, oil storage tanks, and oil level controllers. As an important separation component, the oil separator is installed between the exhaust pipe and the condenser of the refrigeration unit. It is used to separate the refrigeration oil discharged along with the exhaust, ensuring its smooth return to the crankcase of the compressor and guaranteeing the normal operation of the compressor.

3. The relationship between the efficiency of the oil separator and the service life of the compressor

The efficiency of the oil separator is also closely related to the service life of the compressor. If the oil separator is inefficient and fails to effectively separate the lubricating oil, the oil may enter the evaporator, forming an oil film that hinders gas flow and reduces volumetric efficiency. It is pointed out that for refrigeration systems with extremely low temperatures, such as medical low-temperature boxes at -85℃ and -150℃, in addition to using high-efficiency oil separators, special solvents are usually added to prevent lubricating oil from blocking the capillary tubes and expansion valves and to facilitate oil return. In practical applications, the problem of oil return caused by improper design of the evaporator and the return gas pipeline is not uncommon. For the R22 and R404A systems, the oil supply for the flooded evaporator is very difficult, and the design of the system's return oil pipeline must be extremely careful. For such a system, the use of a high-efficiency oil separator can significantly reduce the amount of oil entering the system pipeline and effectively extend the time when there is no oil return in the return pipe after startup.

4. The relationship between the efficiency of oil separators and system energy consumption

The efficiency of the oil separator will also affect the energy consumption of the system. If the oil separator is inefficient and fails to effectively separate the lubricating oil, the oil may enter the evaporator, forming an oil film that hinders gas flow and reduces volumetric efficiency. It is mentioned that an efficient oil separator is used to limit the carrying capacity of lubricating oil to below 500ppm. Lubricating oil is extremely important for the lubrication of screw compressors, the sealing of rotors and cooling. However, lubricating oil in the evaporator may lead to a decrease in heat transfer efficiency and system performance. Therefore, an efficient oil separator can ensure that the lubricating oil circulates only within the lubricating oil circuit, thereby enhancing the heat transfer efficiency.

5. The Relationship between the Efficiency of Oil Separators and system maintenance

The efficiency of the oil separator is also closely related to the maintenance of the system. If the oil separator is inefficient and fails to effectively separate the lubricating oil, the oil may enter the evaporator, forming an oil film that hinders gas flow and reduces volumetric efficiency. It is mentioned that the three-level oil return management technology ensures the reliable and efficient operation of the unit. The first-stage oil return: The compressor is equipped with an internal oil separator. After the oil-gas refrigerant mixture is separated by the internal oil separator of the compressor at the end of the rotor compression, the oil content in the refrigerant is significantly reduced. The second-stage oil return: The refrigerant discharged from the compressor, which contains a small amount of lubricating oil, passes through the second-stage oil separator built into the condenser. The vast majority of the lubricating oil will return to the compressor through the bottom oil return pipe of the oil separator. The third-stage return oil: A very small amount of lubricating oil enters the system along with the refrigerant and remains at the bottom of the evaporator. At this point, the third-stage ejector return oil will pump the lubricating oil completely back to the compressor.

Conclusion

There is a close correlation between the oil separator efficiency of low temperature chiller and the lubrication reliability of the compressor. The higher the efficiency of the oil separator is, the more effectively it can separate the lubricating oil, reduce the entry of lubricating oil into the system, thereby improving the heat exchange efficiency, extending the service life of the compressor, reducing the energy consumption of the system, and enhancing the operational reliability of the system. Therefore, when designing and selecting a low temperature chiller, the efficiency of the oil separator should be fully considered to ensure the normal operation of the compressor and the efficient operation of the system.