The invention relates to a process for cooling or heating a fluid or a body by means of a vapour compression circuit comprising a
centrifugal compressor and containing a heat-transfer fluid, the heat-transfer fluid comprising at least two compounds selected from 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoropropene, 1,1-difluoroethane and 3,3,3-trifluoropropene, in which: the ratio of the Mach number of the
centrifugal compressor to the Mach number which the
centrifugal compressor has under the same operating conditions if the heat-transfer fluid is replaced with 1,1,1,2-tetrafluoroethane in the vapour compression circuit is greater than or equal to 0.97 and less than or equal to 1.03; the
compression ratio of the centrifugal compressor is less than or equal to the
compression ratio which the centrifugal compressor has under the same operating conditions if the heat-transfer fluid is replaced with 1,1,12-tetrafluorethane in the vapour compression circuit. The invention also relates to equipment suitable for implementing this cooling or heating process, and also to a process for converting existing equipment.