Multistage compression system

A multistage compression system using refrigerant and oil, the multistage compression system comprising:

• a low-stage compressor configured to compress the refrigerant;
• a high-stage compressor configured to further compress the refrigerant compressed by the low-stage compressor;
• first and second refrigerant pipes configured to introduce the refrigerant compressed and discharged by the low-stage compressor into a suction part of the high-stage compressor;
• an intercooler configured to cool the refrigerant discharged by the low-stage compressor before the refrigerant is sucked into the high-stage compressor, the intercooler being disposed between the first and second refrigerant pipes;
• and
• an oil discharge pipe configured to discharge the oil in the low-stage compressor, the intercooler being configured to cool the refrigerant discharged by the low-stage compressor before the refrigerant is sucked into the high-stage compressor, the oil discharge pipe being connected to the intercooler, and the oil discharge pipe being configured to supply the oil discharged from the low-stage compressor to the intercooler,
• the first refrigerant pipe being configured to discharge the refrigerant from the low-stage compressor and to supply the refrigerant to the intercooler, and the second refrigerant pipe being configured to supply the refrigerant from the intercooler to the suction-part of the high-stage compressor.