The present invention relates to compositions for use in refrigeration and
air-conditioning systems comprising
1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane and at least one
hydrocarbon. Further, the present invention relates to compositions for
use in refrigeration and air-conditioning systems employing a centrifugal
compressor comprising 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane at
least one hydrocarbon. The compositions of the present invention may be
azeotropic or near-azeotropic and are useful in processes for producing
cooling or heat or as heat transfer fluids.