The recovery of refrigerant oil has always been a hot topic in the refrigeration system of Transport Refrigeration Unit and Parking Air Conditioner. Today, Corunclima would like to talk about the refrigerant oil return in screw compressor.

Generally speaking, the main reason why the screw compressor is not easy to recover the refrigerant oil is the mixture of lubricating oil and refrigerant during the operation. In the operation of the refrigeration system, the refrigerant and the refrigerant oil mutually dissolve, causing the lubricating oil to be discharged into the condenser with the refrigerant in the form of air mist and micro droplet. If the oil separator does not work well or the system design is not good, it will cause poor separation effect and poor oil return.

What problems will there be if the recovery of refrigerant oil is not smooth?

The failure of oil recovery in screw compressor will cause a large amount of lubricating oil to stay in the evaporator pipe. When the oil film increases to a certain extent, it will directly affect the cooling performance of the system. On the other hand, the machine is unable to run if the refrigerant oil is insufficient, so it is necessary to replenish the refrigerant oil constantly. This will lead to the accumulation of the lubricating oil in the system, causing a vicious cycle, increasing operation cost and reducing the reliability of operation. Under normal circumstances, less than 1% of the mixture of oil and gas in the refrigerant gas flow in the system is allowed.

The oil separator is installed on the exhaust pipe of the compressor, and it can generally separate out 50-95% running oil. The oil recovery effect is good and the speed is fast. It greatly reduces the amount of oil entering the system pipeline, thus effectively prolongs the running time under no return oil.

Frequent starting of compressor is not conducive to oil recovery. Because of the short running time, the compressor stops when there is no time to form a steady high speed airflow in the return pipe, thus the oil will be stuck in the pipes. When the oil returned is less than the running oil in the pipes, the compressor will be short of oil. The shorter the operation time is, the longer the pipeline is, the more complex the system is, the more prominent the oil return problem will be. Therefore, do not start the compressor frequently.

So, how to accelerate the recovery of refrigerant oil?

Lack of oil can cause serious insufficient lubrication issue. The root cause of the lack of oil is not the quantity nor the speed of running oil, but the poor oil return. The installation of oil separator can quickly return oil and extend the operation time of the compressor with no oil returned. The design of evaporator and return piping must take into account the return of oil. Some measures such as avoiding frequent startups, regular defrosting, timely replenishment of refrigerants, and timely replacement of vulnerable parts (such as bearings) will also help to accelerate the return of refrigerant oil.

Together with Corunclima, let’s enjoy the comfort brought by worry-free transport refrigeration unit and air-conditioning system for trucks, vans, and various types of vehicles!