Optimized point of injection of liquid refrigerant in a helical screw rotary compressor for refrigeration use

摘要

A helical screw rotary compressor within a refrigeration system is provided with a liquid refrigerant injection port opening into the working space of the compressor for injecting liquid refrigerant bled from the refrigeration system condenser at essentially compressor discharge pressure. The port is located at the optimum point of injection by determining; the minimum built-in volume ratio of the compressor, the rotor bore within which injection is to take place, the minimum and maximum system or operating compression ratios and by correlating these parameters with the pressure versus wrap angle plot for the selected compressor rotor bore. The acceptable injection point for the injection port is thus determined in terms of the wrap angle from the suction side of the compressor for the screw rotor of the selected bore where continuous pressure injection of liquid refrigerant occurs within the working space regardless of undercompression or overcompression of the working fluid without significantly compromising compressor efficiency.