Abstract: A method of cooling a process stream with an auxiliary stream is described, wherein the exchange of heat between the process stream and the auxiliary stream is effected in a first heat exchanger and a second heat exchanger connected downstream thereof.

Abstract: A method for controlling speeds of compressors arranged in series for compressing a fluid. The desired inlet pressure is predefined and the actual inlet pressure is detected. The actual discharge pressure of the fluid is recorded and the actual total pressure ratio is recorded. A proportional integral value is determined from the deviation of the actual inlet pressure from the desired inlet pressure and a capacity factor is determined from the proportional integral value and the actual total pressure ratio. A model total pressure ratio is determined from the actual total pressure ratio and the capacity factor. A reduced desired speed for each compressor is determined as a function value of the control function associated with the respective compressor. The control function assigns a reduced desired speed to each value pair of capacity factor and model total pressure ratio and is used to adjust the speed of each compressor.

Abstract: A method of cooling a process stream with an auxiliary stream is described, wherein the exchange of heat between the process stream and the auxiliary stream is effected in a first heat exchanger and a second heat exchanger connected downstream thereof.

Abstract: A method for controlling speeds of compressors arranged in series for compressing a fluid. The desired inlet pressure is predefined and the actual inlet pressure is detected. The actual discharge pressure of the fluid is recorded and the actual total pressure ratio is recorded. A proportional integral value is determined from the deviation of the actual inlet pressure from the desired inlet pressure and a capacity factor is determined from the proportional integral value and the actual total pressure ratio. A model total pressure ratio is determined from the actual total pressure ratio and the capacity factor. A reduced desired speed for each compressor is determined as a function value of the control function associated with the respective compressor. The control function assigns a reduced desired speed to each value pair of capacity factor and model total pressure ratio and is used to adjust the speed of each compressor.

Abstract: A method and apparatus for a refrigeration circuit is disclosed. In the refrigeration circuit, a single-component or multi-component refrigerant, preferably a nitrogenous refrigerant, in particular nitrogen, circulates, where at least one partial stream of the refrigerant is expanded. The expansion of the refrigerant takes place in at least two expansion turbines that are arranged in series, and the temperature of the refrigerant at the exit of the expansion turbines, or at least at one of the exits of the expansion turbines, is above the saturation temperature of the refrigerant. In this connection, the temperature of the refrigerant at the exit of the expansion turbines, or at least at one of the exits of the expansion turbines, is less than 10° C., preferably less than 5° C., in particular less than 2° C., above the saturation temperature of the refrigerant.