Refrigerating system adopting single-stage serial middle air supply centrifugal compressor

The invention discloses a refrigerating system adopting a single-stage serial type middle air supply centrifugal compressor, and relates to the field of compressors, the refrigerating system comprises a serial type middle air supply refrigerating centrifugal compressor, a condenser and an air supply distributor, and a closed impeller is arranged in the serial type middle air supply refrigerating centrifugal compressor; a refrigerant side inlet of the condenser is communicated with the exhaust side of the closed impeller; a refrigerant outlet of the evaporator is communicated with the air suction side of the closed impeller through a fourth pipeline; the closed impeller comprises a wheel disc and a wheel cover which are covered with each other, a first circle of blades and a second circle of blades are arranged in the wheel disc and the wheel cover, a plurality of air supplementing holes are formed in the positions, between the first circle of blades and the second circle of blades, of the wheel cover, and the