Cooling and/or liquefying method and system

A system for cooling and/or liquefying a flow of user fluid, comprising:

• a low-temperature refrigeration device for refrigeration at a temperature of between minus 100 degrees centigrade and minus 273 degrees centigrade, the refrigeration device comprising a working circuit that forms a loop and contains a working fluid and a cooling exchanger that is configured to extract heat from the flow of user fluid by heat exchange with the working fluid circulating in the working circuit, the working circuit forming a cycle comprising, in series:
• one or more compressors configured to compress the working fluid, a cooling line of a working circuit heat exchanger configured to cool the working fluid, a turbine configured to expand the working fluid, a beating line within the cooling exchanger configured to heat the working fluid, and a beating line of the working circuit heat exchanger configured to beat the working fluid;
• a tank of user fluid;
• a circulation duct for said flow of user fluid to be cooled in heat exchange with the cooling exchanger of the refrigeration device;
• and
• an electronic controller for controlling the refrigeration device, said controller being configured to:
• switch operation of the refrigeration device into a cooling mode in which the cooling exchanger is cooled by the working gas in order to cool a flow of user fluid or into a stopped mode in which the circulation of the working fluid in the working circuit is interrupted;
• and
• switch operation of the system into a configuration for cleaning away impurities that have solidified in the cooling exchange in which the refrigeration device is switched into its stopped mode, and simultaneously, a flow of the user fluid is made to circulate in the cooling exchanger by pumping the user fluid into the circulation duct from a liquid phase of the user tank and return the circulated user fluid to the user tank by raining down into a gas phase of the tank.