The capacity of the refrigeration system could be increased by using the economizer

but the COP would not be improved equally due to the increased compressor power consumption from super feeding

and the improvement of COP depends mainly upon the parameters such as superfeed pressure

superfeed port location. In this study

the thermodynamic processes of the twin-screw refrigeration compressor at different superfeed pressures were investigated by analyzing the indication diagrams recorded in the twin-screw refrigeration compressor with an economizer

and the influence of the super-feed pressure on the compressor efficiency and system COP was obtained. The results show that the gas pressure in working chamber experiences a rapid increase as super-feed gas enters the chamber

and then a slow rise

and finally the pressure has a slight drop at the late phase of the super-feeding process. Correspondingly

the compressor efficiency and COP rise first and then drop

depending upon the superfeed pressure. As a result

there is an optimum superfeed pressure under which the system COP reaches the best.