Use of mixtures based on difluoromethane and on pentafluorethane as cryogenic fluids in very low temperature refrigeration
AssigneeElf Atochem S.A.
InventorSylvie Macaudiere
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Abstract
To replace bromotrifluoromethane (R-13B1) in very low temperature refrigeration, the invention proposes to employ a mixture containing, on a mass basis, 25 to 50% of difluoromethane and 50 to 75% of pentafluoroethane. A third component may be incorporated in this mixture.
Claims6
A method of operating a low temperature refrigeration system having an evaporation temperature of less than -45.degree. C. and designed for R-13B1 comprising formulating a quasi-azeotropic mixture containing, on a mass basis, 25 to 35% of difluoromethane and 65 to 75% of pentafluoroethane as cryogenic fluid, and replacing the R-13B1 with said mixture;
- wherein said mixture (i) exhibits a difference in pressure between its bubble and dew points of less than one-percent, (ii) has a boiling point of less than -51.degree. C. and (iii) is nonflammable.
A method of operating a low temperature refrigeration system having an evaporation temperature of less than -45.degree. C. and designed for R-13B1 comprising the steps of formulating a quasi-azeotropic mixture consisting essentially of, on a mass basis, (i) 25 to 35% of difluoromethane, (ii) 65 to 75% of pentafluoroethane as cryogenic fluid, and (iii) up to 12% of trifluoromethane or up to 20% of 1,1,1-trifluoroethane;
- and replacing the R-13B1 with said mixture;
- wherein said mixture (i) exhibits a difference in pressure between its bubble and dew points of less than one-percent, (ii) has a boiling point of less than -51.degree. C., and (iii) is nonflammable.
Dependencies are inferred from the claim text.