Abstract: The injection structure is one of the key factors that restrict the efficiency of injecting refrigerant oil in air conditioning system. To study the advantages and disadvantages of three commonly used oil injection structures, the experiment tested and analyzed the change of time and pressure in the whole process of vacuum oil injection. The results showed that the oil injection structures of the globe valve and the internal thread fluorine injection nozzle has the higher efficiency than the external thread fluorine injection nozzle. The globe valve generally takes more time to install and remove the joints and other preparations than the fluorine injection nozzle. The three processes of vacuum oil injection all lead to pressurizing of the system, thereby affecting the efficiency of the subsequent processes. Considering the oil injection time, operating efficiency and the pressure rise of the system after that the refrigerant oil has been injected, the internal threaded fluorine injection nozzle is the best choice for the vacuum oil injection structure. The results provide reference for the oil injection structure design of air conditioning system.

Key words: Refrigerant oil, Oil injection structure, Pressure, Efficiency