Disclosed is a refrigeration and/or liquefaction method using a system that includes a low-temperature refrigeration device comprising a working circuit which forms a loop and contains a working fluid, the working circuit forming a cycle comprising, connected in series: a compression mechanism, a cooling mechanism, an expansion mechanism and a heating mechanism the refrigeration device further comprising a cooling exchanger for extracting heat from the useful fluid stream by exchanging heat with the working fluid flowing in the working circuit, the system comprising a pipe through which the useful fluid stream flows in the cooling exchanger, the method comprising a cooling step in which the refrigeration device is in a first operating mode for cooling the cooling exchanger while a useful fluid stream flows in the cooling exchanger, the method comprising, after said cooling step, a step of cleaning impurities that have solidified in the cooling exchanger, characterized in that during the cleaning step, the refrigeration device is in a second operating mode in which the working gas flows in the working circuit but in which the cooling exchanger cools less intensely than in the first operating mode.

A system for controlling a capacity of a compressor includes a motor of the compressor including a main winding connected at a connection point to an auxiliary winding and a drive configured to control a speed of the motor. The system includes a first switch configured to selectively connect the main winding to either a first line voltage or a first output of the drive, a second switch configured to selectively connect the connection point to either a second line voltage or a second output of the drive, and a third switch configured to selectively connect the auxiliary winding to either a capacitor or a third output of the drive. The system includes a solenoid valve configured to selectively either operate in a first capacity or a second capacity. The system includes a control module configured to control the drive, the first switch, the second switch, and the third switch.

A refrigeration cycle including at least one outdoor unit including a plurality of compressors and indoor units each placed in indoor spaces comprises a plurality of compressors for supplying refrigerant to indoor units; and a controller for controlling cooperatively a plurality of the compressors in the outdoor unit to provide a capacity for air-conditioning in the indoor spaces through the indoor units, wherein the controller controls operation of the compressors so as to minimize a cost including start/stop of each compressor by prediction of an air-conditioning requirement in a next time chunk.

A system for controlling a capacity of a compressor includes a motor of the compressor including a main winding connected at a connection point to an auxiliary winding and a drive configured to control a speed of the motor. The system includes a first switch configured to selectively connect the main winding to either a first line voltage or a first output of the drive, a second switch configured to selectively connect the connection point to either a second line voltage or a second output of the drive, and a third switch configured to selectively connect the auxiliary winding to either a capacitor or a third output of the drive. The system includes a solenoid valve configured to selectively either operate in a first capacity or a second capacity. The system includes a control module configured to control the drive, the first switch, the second switch, and the third switch.

Method for controlling a compressor system, arranged in a heat pumping circuit, said compressor system being designed to be operated at at least two different compressor capacity stages, said compressor capacity stages being adjusted by a capacity adjustment system enabling switching from one compressor capacity stage to another compressor capacity stage, said capacity adjustment system being controlled by a capacity selection signal defining the compressor capacity stage to be selected, said method comprising determining a capacity set value, determining a decision quantity on the basis of said capacity set value, determining a calculated capacity average value on the basis of capacity selection signals generated before, comparing said calculated capacity average value with said decision quantity and changing said compressor capacity stage to the next higher stage if the calculated capacity average value is below the decision quantity or changing said compressor capacity stage to the next lower stage if the calculated capacity average value is above the decision quantity, or not changing said compressor capacity stage if the calculated capacity average value meets said decision quantity.

A refrigeration cycle including at least one outdoor unit including a plurality of compressors and indoor units each placed in indoor spaces comprises a plurality of compressors for supplying refrigerant to indoor units; and a controller for controlling cooperatively a plurality of the compressors in the outdoor unit to provide a capacity for air-conditioning in the indoor spaces through the indoor units, wherein the controller controls operation of the compressors so as to minimize a cost including start/stop of each compressor by prediction of an air-conditioning requirement in a next time chunk.

A control system for controlling an output for a plurality of compressors includes a control unit receiving a first value from a first sensor and generating a first output based on the first value. The control unit receives a second value from a second sensor and derives a final output from the first output and the second value. A plurality of compressors receives the control commands from the control unit based on the final output.

A climate-control system includes a variable-capacity compressor. An outdoor ambient temperature sensor indicates a temperature of the outdoor ambient air. A return air temperature sensor indicates a temperature of the return air in the system. A controller commands a startup compressor stage based on the temperature from the outdoor ambient temperature sensor and commands a running compressor stage based on a time-based slope of the temperature from the return air temperature sensor and the startup compressor stage.

An air conditioner that is a refrigeration apparatus has, in a refrigerant circuit, a compressor, an outdoor heat exchanger that functions as an evaporator in a heating operation, an indoor heat exchanger that functions as a condenser in the heating operation, and a four way valve. The refrigerant circuit is configured in such a way that a high-pressure value of the refrigerant circuit in a defrost operation is lower than a high-pressure value of the refrigerant circuit in the heating operation. An end-of-defrost frequency decrease rate, which is a rate of decrease in the operating frequency of the compressor in the defrost operation, is set faster than a normal frequency decrease rate, which is a rate of decrease in the operating frequency of the compressor in the heating operation.

A system includes a dynamic compressor and a controller having a processor and a memory. The compressor includes a first compressor stage having a first variable inlet guide vane (VIGV) and a second compressor stage having a second VIGV. The memory stores instructions that program the processor to operate the compressor at a current speed, a first position of the first VIGV, and a second position of the second VIGV to compress the working fluid, and to determine if a condition is satisfied. If the condition is not satisfied, the processor is programmed to continue to operate the compressor at the current speed, the first position of the first VIGV, and the second position of the second VIGV. If the condition is satisfied, the processor is programmed to change the second position of the second VIGV to a third position and maintain the first position of the first VIGV.