Three-stage cascade refrigeration system lubricated with polyester oil

Abstract

The invention discloses a refrigerant applicable to a three-stage cascade refrigeration system using polyester oil for lubrication. The refrigerant comprises a high-temperature-stage refrigeration unit, a medium-temperature-stage refrigeration unit and a low-temperature-stage refrigeration unit, wherein a mixture of pentafluoroethane / trifluoroethane / tetrafluoroethane is used as a refrigerant for the high-temperature-stage refrigeration unit; difluoromethane is used as a refrigerant for the medium-temperature-stage refrigeration unit; a mixture of carbon tetrafluoride and difluoromethane is used as a refrigerant for the low-temperature-stage refrigeration unit; the mass ratio of the carbon tetrafluoride to the difluoromethane is 20:1. The refrigerant has the advantages that the problems of blockage of a throttling device and instable work of a refrigeration system due to high probability of freezing of the polyester oil existing in the three-stage cascade refrigeration system using polyester oil for lubrication are solved, and meanwhile the ozone layer loss substances of the mixture of the carbon tetrafluoride and the difluoromethane are equal to zero so as to meet the environmental requirements.

Description

technical field [0001] The invention relates to a three-stage cascade refrigeration system, in particular to a three-stage cascade refrigeration system lubricated by polyester oil. Background technique [0002] At present, in the low-temperature refrigeration technology at -120°C, a three-stage cascade refrigeration system is usually used. The basic principle of the three-stage cascade refrigeration system is to use the high-temperature stage refrigeration unit, the medium-temperature stage refrigeration unit and the low-temperature stage refrigeration unit to cascade to make the temperature reach -120°C. In order to meet environmental protection requirements, high-temperature refrigeration units mostly use a mixture of pentafluoroethane / trifluoroethane / tetrafluoroethane (R-404A) as a refrigerant, and medium-temperature refrigeration units mostly use difluoromethane (R-32 ) as the refrigerant, and low-temperature refrigeration units generally use carbon tetrafluoride (R-14)...

AI Technical Summary

Problems solved by technology

However, when the low-temperature refrigeration unit uses carbon tetrafluoride as the refrigerant, carbon tetrafluoride and polyester oil are incompatible, which makes the polyester oil easy to freeze when carbon tetrafluoride flows through the throttling device under low-temperature conditions. Cause the throttling device to be blocked, and the refrigeration system has poor working stability

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