USE OF MIXTURE MAINLY COMPRISING DIFLUOROMETHANE AND PENTAFLUOROETHANE AS REFRIGERANT FOR CRYOGENIC REFRIGERATION

摘要

PROBLEM TO BE SOLVED: To obtain a refrigerant for cryogenic refrigeration which is nonflammable, can substitute for bromotrifluoromethane (R-13B1), and does not influence or hardly influences on the environment by mixing difluoromethane with pentafluoroethane at a specified ratio. SOLUTION: A mixture comprising 25-50 mass % difluoromethane (HFC-32) and 50-75 mass % pentafluoroethane (HFC-125) is used as a refrigerant for cryogenic refrigeration. If necessary, the mixture may further contain 12 mass % or lower trifluoromethane (HFC-23) or 20 mass % or lower 1,1,1- trifluoroethane (HFC-143a). The mixture enables a refrigerant bath temp. of about -54 deg.C to be obtd., while that obtd. with R-13B1 is -59 deg.C. Though the mixture requires a little higher compressor pressure, its cooling rate is higher and hence energy saving of about 40% is possible.