Device and method for refrigerating or liquefying a fluid

A device for refrigeration or liquefaction of a fluid, the device comprising:

• a circuit for fluid that is to be cooled, having an upstream end intended to be connected to a source of gaseous fluid and a downstream end intended to be connected to a member for collecting the cooled or liquefied fluid;
• an assembly of heat exchanger(s) in a heat exchange relationship with the circuit for fluid that is to be cooled;
• a refrigerator in a heat exchange relationship with at least part of the assembly of heat exchanger(s), the refrigerator configured to perform a refrigeration cycle on a cycle gas, the cycle gas selected from the group consisting of:
• helium, hydrogen, nitrogen, neon, and combinations thereof,
• said refrigerator comprising the following, disposed in series in a cycle circuit:
• a compression mechanism configured to compress the cycle gas,
• at least one cooling member configured to cool the cycle gas,
• an expanding mechanism configured to expand the cycle gas, and
• at least one heating member configured to heat the expanded cycle gas,
• wherein the compression mechanism comprises multiple compression stages in series that are composed of an assembly of compressor(s) of centrifugal type,
• wherein the compression stages are mounted on a set of shafts driven in rotation by an assembly of motor(s),
• wherein the at least one cooling member comprises at least one heat exchanger disposed at the outlet of at least one compression stage in a heat exchange relationship with the cycle circuit,
• wherein said heat exchanger is cooled by a heat transfer fluid,
• wherein the compression mechanism comprises at least two compression stages that are disposed successively in series and do not have a member for cooling the cycle gas such as a heat exchanger for exchanging heat between them,
• wherein the assembly of motor(s) comprises multiple motors for driving the compression stages,
• wherein at least one of the motors is cooled by a flow of cycle gas via at least one bypass pipe for a fraction of the flow of cycle gas supplying the compression mechanism, and
• wherein the bypass pipe comprises an upstream end attached to the outlet of at least one of the compression stages for drawing off a fraction of the flow of cycle gas.