Patent attributes
The invention provides a freezer unit using refrigerants serving as an oil carrier without using any refrigerants of subjects of the ozone regulation and being capable of realizing extremely low temperatures such as −150° C. The freezer unit includes a refrigerant circuit on a high temperature side and a refrigerant circuit on a low temperature side to form independent closed refrigerant circuits which condense refrigerants delivered from compressors and thereafter evaporate the condensed refrigerants to achieve cooling action, and a cascade condenser formed by an evaporator in the refrigerant circuit on the high temperature side and a condenser in the refrigerant circuit on the low temperature side. Confined in the refrigerant circuit on the low temperature side are nonazeotropic mixed refrigerants containing R245fa, R600, R404A, R508A, R14, R50 and R740, or nonazeotropic mixed refrigerants containing R245fa, R600, R404A, R23, R14, R50 and R740, or nonazeotropic mixed refrigerants containing R245fa, R600, R404A, R508B, R14, R50 and R740.
