Before returning to the compressor refrigeration cycle system, when the refrigerant must complete gasification. So before the refrigerant entering the compressor must be gas and liquid separation, let the gaseous refrigerant entering the compressor, don't let too much liquid compressor and refrigerant and dilute compressor oil. Liquid refrigerant in the machine body slowly evaporates, after waiting for evaporation into the compressor. In order to make the remaining frozen oil back to the compressor in the system, at the bottom of the muffler in the gas-liquid separator is equipped with oil return hole, in the system in the remaining frozen oil to gas liquid separator, will be back in the compressor with gas refrigerant. With the protection of the gas-liquid separator, the life of the compressor will be more durable, circulation system to a more normal.