Refrigeration and/or liquefaction device using selective pre-cooling, and corresponding method

A device for the refrigeration and/or liquefaction of a working gas containing helium or consisting of pure helium, the device comprising a working circuit in the form of a loop for the working gas and comprising, in series:

• a working gas compression station equipped with at least one compressor,
• a cold box for cooling the working gas and comprising a plurality of heat exchangers arranged in series and at least one turbine for expanding the working gas,
• a system for an exchange of heat between the cooled working gas and a point of use,
• at least one return pipe returning to the compression station the working gas that has passed through the system for the exchange of the exchange of heat between the cooled working gas and the point of use, at least one return pipe comprising at least one exchanger for warming the working gas, the device further comprising an additional system for pre-cooling the working gas at the exit from the compression station, the additional system comprising a volume of auxiliary cryogenic fluid, the volume being connected to the working circuit via at least one heat exchanger in order to selectively transfer negative calories from the auxiliary cryogenic fluid to the working gas using a plurality of valves, the cold box comprising a first working-gas cooling stage comprising a first and a second heat exchanger which are connected both in series and in parallel, using the plurality of valves, to the working circuit at the outlet of the compression station, such that the working gas leaving the compression station can be admitted selectively, using the plurality of valves, to the first and/or to the second heat exchanger, the first cooling stage also comprising a third heat exchanger selectively in a heat-exchange relationship with the auxiliary fluid, such that the third heat exchanger is connected both in series and in parallel to the first and second heat exchangers, such that the gas leaving the first and/or the second heat exchanger is admitted selectively, using the plurality of valves, to the third heat exchanger, wherein the working circuit comprises a recovery pipe fitted with at least one recovery valve and which connects an outlet of the third heat exchanger to the second heat exchanger so as to allow, selectively, the transfer of negative calories from the working gas leaving the third heat exchanger to the second heat exchanger.