Disclosed herein is an
air conditioning or
refrigeration apparatus, and in particular, a
chiller apparatus containing a composition comprising 1,1,1,4,4,4-hexafluoro-2-
butene and 1,2-dichloroethylene, wherein the 1,1,1,4,4,4-hexafluoro-2-
butene is cis isomer or primarily cis isomer and wherein the 1,2-dichloroethylene is trans isomer or primarily trans isomer. These chillers may be flooded evaporators or direct expansion evaporators, which utilize centrifugal compressors. Also disclosed herein are methods for producing cooling comprising evaporating a composition comprising cis-1,1,1,4,4,4-hexafluoro-2-
butene and trans-1,2-dichloroethylene in the vicinity of a body to be cooled. Also disclosed herein are compositions comprising cis-1,1,1,4,4,4-hexafluoro-2-butene and trans-1,2-dichloroethylene, wherein the cis-1,1,1,4,4,4-hexafluoro-2-butene is present at 50 to about 60 weight percent.