Principle and role of lubricating oil in the refrigeration system of chiller
In a compression refrigeration system, the compressor must lubricate the moving parts. The lubricating oil in the machine is more or less moved by the air flow during the continuous transport of the working fluid, and enters other equipment in the system. After the condenser and evaporator, it will cause harm to the system. To make the system operate efficiently and energy-saving, corresponding measures must be taken. There are two main reasons why lubricating oil can enter the system: one is the exhaust speed of the compressor. According to the moving star law, the greater the speed, the larger the oil droplets that can be carried; The increase in oil speeds up the evaporation of the oil. In fact, the influence of oil on the heat exchange equipment in the refrigeration system is related to the mutual solubility of the refrigerant and the oil. The dissolution relationship between the Freon refrigerant and the oil varies with the type and temperature of the Freon. The more fluorine atoms contained in Freon, the lower the solubility in lubricating rain. The commonly used refrigerants R11 and R12 are completely dissolved with the oil, which can be artificially independent of temperature, while R22 is temperature-dependent. Generally, it can be completely dissolved in the condensation, and partially dissolved in the evaporator. Above the solvent) and the lean layer (in the refrigerant). In the working fluid, when the two types of mutual solubility increase, the impact on the system is relatively small, otherwise, it is greater.
The characteristics of the working fluid in the Freon refrigeration system are easy to dissolve in the lubricating oil, so the system lubricating oil must take a reflux cycle. During the operation of the system, ensuring the normal circulation of lubricating oil and maintaining a stable oil level in the compressor crankcase are necessary conditions for the normal and safe operation of the system. This requires the lubrication oil circulation balance when the system is running, that is, the amount of oil carried out by the exhaust gas should be equal to the amount of oil returned to the crankcase of the compressor every moment. The return of the lubricating oil is firstly returned to the compressor after passing through the oil separator; the second is that there are no technical measures to ensure the return on the return air pipe. For the liquid supply method of the upper and lower evaporating pipes, coolers, etc., when using a thermal expansion valve to supply liquid directly, the oil can be brought back by using a high return air speed. For the design of the piping in the Freon refrigeration system, the optimal pipe diameter of the return air pipe should be calculated according to the specific situation and designed into the corresponding form. For some upward and downward evaporation tubes, shell-and-tube evaporators, etc., there is more refrigerant in the equipment's memory, and the oil cannot be returned by the borrowed air speed. At this time, "liquid extraction" must be performed. Similar to the air infiltration system, the entry of oil will also increase the cold screw pressure and increase the power consumption of the system. Therefore, the system should be equipped with an oil separator and a reliable oil return pipeline as much as possible to ensure the reliability of system operation.
The above is the principle and role of lubricating oil in the refrigeration system of chiller. For more related knowledge, please visit http://ylscps.com