Compressor oil return is not smooth how to deal with?

Compressor oil return is not smooth how to deal with?

  The oil return problem of refrigeration compressor has always been a hot topic of refrigeration system, in general, the reason for the poor oil return of screw compressor is mainly because of the gas mixing phenomenon of lubricating oil and refrigerant during operation. In the operation of the refrigeration system, the refrigerant and the refrigerator lubricating oil are misintegrated, resulting in the lubricating oil and the refrigerant being discharged into the condenser in the form of gas mist and microdroplets. If the oil separator effect is not good or the systemdesign is not good, it will cause poor separation effect and poor system oil return problem.

  The oil return of the screw compressor is not smooth, which will lead to a large number of lubricating oil remaining in the evaporator pipeline, and when the oil film increases to a certain extent, it will directly affect the system cooling; On the other hand, the machine can not run without oil, and it needs to constantly replenish lubricating oil, which will lead to the accumulation of lubricating oil in the system, resulting in a vicious cycle, increasing operating costs and reducing operating reliability. Under normal circumstances, less than 1% of the refrigerant gas flow rate of the oil and gas mixture is allowed to circulate in the system.

  There are two ways to return oil to the compressor, one is to return oil to the oil separator, and the other is to return oil to the gas pipe. The oil separator is installed on the compressor exhaust pipe, generally can separate 50-95% of the oil, the oil return effect is good, the speed is fast, greatly reducing the amount of oil entering the system pipeline, so as to effectively extend the operation time without oil return. The pipeline is particularly long cold storage refrigeration system, full liquid ice making system and very low temperature freeze-drying equipment, etc., ten minutes or even tens of minutes after the boot does not return the oil or the amount of oil is very small is not rare, poor design system will appear compressor oil pressure is too low and shut down the problem. The high efficiency oil separator installed in this refrigeration system can greatly extend the operation time of the compressor without oil return, so that the compressor can safely pass the crisis stage of no oil return after starting up. The lubricating oil that is not separated will enter the system and flow with the refrigerant in the tube to form an oil circulation. After the lubricating oil enters the evaporator, on the one hand, due to the low temperature and small solubility, a part of the lubricating oil is separated from the refrigerant; On the other hand, the temperature is low and the viscosity is large, and the separated lubricating oil is easy to adhere to the tube wall, and the flow is more difficult. The lower the evaporation temperature, the more difficult it is to return the oil. This requires that the design of the evaporation pipeline and the design and construction of the return pipe must be conducive to the return of oil, and the common practice is to use the descending pipeline design and ensure the larger airflow speed. For refrigeration systems with particularly low temperatures, in addition to the selection of high-efficiency oil separators, special solvents are usually added to prevent lubricating oil from plugging capillary tubes and expansion valves, and to help return oil.

Shanghai KUB Refrigeration Equipment Co., Ltd.

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