Disclosed herein are refrigerant and heat transfer fluid compositions comprising 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone and at least one hydrofluorocarbon for use in refrigeration and air conditioning systems employing a centrifugal compressor. The compositions may be azeotropic or near-azeotropic.