a centrifugal compressor for compressing a refrigerant vapor in a refrigeration cycle . the compressor comprises an impeller drive shaft supported by first and second radial bearings for rotation within the compressor housing and an impeller assembly including at least one centrifugal impeller wheel mounted on the impeller drive shaft to rotate with the impeller drive shaft . the first and second radial bearings are hydrodynamic fluid bearings in which the bearing fluid is the refrigerant vapor . the compressor further comprising a conduit for supplying a portion of the refrigerant vapor from the impeller assembly to the first and second fluid bearings .