The economizer produced by our company is suitable for commercial central air-conditioning units. Its main function is: the high-pressure liquid refrigerant from the condenser is divided into two parts after entering the economizer. One part is further cooled by throttling and heat expansion to reduce the temperature of the other part and make it supercooled. The supercooled liquid is cooled directly through the feed valve directly into the evaporator. The other part of uncooled gas refrigerant through the economizer and compressor pipeline, re-enter the compressor to continue compression, into the cycle. It expands the refrigeration mode to stabilize the liquid refrigerant medium, so as to improve the capacity and efficiency of the system.