Refrigeration system

Refrigeration system comprising a refrigerant circuit, a main mass flow of a refrigerant being guided in said circuit, a refrigerant-cooling heat exchanger arranged in the refrigerant circuit on the high pressure side, an expansion cooling device arranged in the refrigerant circuit, said device cooling the main mass flow of the refrigerant in the active state and thereby generating an additional mass flow of gaseous refrigerant, a reservoir for liquefied refrigerant arranged in the refrigerant circuit, at least one expansion unit for liquefied refrigerant of the main mass flow, said expansion unit being arranged in the refrigerant circuit and having an expansion element and a post-connected heat exchanger on the low pressure side, said heat exchanger making refrigerating capacity available, and at least one refrigerant compressor arranged in the refrigerant circuit, said compressor having a main compressor stage and at least one additional compressor stage driven together with the main compressor stage, said two stages compressing refrigerant to high pressure PH, wherein the main compressor stage and the at least one additional compressor stage are adapted to be used such that either the main compressor stage compresses refrigerant from the main mass flow and the additional compressor stage compresses refrigerant from the additional mass flow or the main compressor stage and the additional compressor stage compress refrigerant from the main mass flow, at least two refrigerant compressors being arranged in the refrigerant circuit, said compressors being adapted to be switched on individually for the purpose of compressing the main mass flow, at least two of the refrigerant compressors each have at least one additional compressor stage, wherein each of the additional compressor stages is adapted to be used optionally for the compression of refrigerant from the main mass flow or for the compression of refrigerant from the additional mass flow and a control provided for switching in a first operating mode as a function of the operating conditions on such a number of additional compressor stages for the compression of refrigerant from the additional mass flow that the expansion cooling device liquefies the main mass flow and reduces its enthalpy.