Abstract: The invention relates to a compressor assembly, where the inlet port of a liquid-piston rotary compressor is coupled to a suction line and the outlet port of the compressor is coupled to a storage tank. An air-discharge line and a return line leading to the liquid-piston rotary compressor are coupled to the storage tank which recirculate operating liquid. Furthermore, an after-cooler device having a primary and a secondary zone is provided, which is connected with its primary zone to the suction line and, its secondary zone, to the air-discharge line. The condensate being produced in the after-cooler device is recirculated into the circulation zone of the operating liquid.