Abstract: A mechanical compressor system is provided. In the system, a suction line is connected to a first connecting port of a liquid ring compressor, and an exhaust line is connected to a second connecting port of the same. An after-cooler unit is provided which consists of two separate chambers having at least one separating wall and which is arranged with its first chamber in the suction line and with its second chamber in the exhaust line. At least one injection line is provided for injecting fluid from the return line into the suction line upstream from the after-cooler unit, or in the after-cooler unit. Thus, the gaseous working fluid is allowed to be cooled to process-compatible temperatures with only a low power demand and little additional expenditure for installation.

Abstract: An apparatus for improving the operating efficiency of a liquid-flow machine comprises a sensor for measuring the liquid throughput of the liquid-flow machine and a dosing device for controlling, in response to the measured throughput, the amount of a friction-reducing agent added to inflowing working fluid. The friction reducing agent preferably consists of marcomolecular bodies such as polyacrylamides or tensides. Inorganic fiber is also possible as an additive for reducing friction in the liquid-flow machine.