2H-Ne-He as the Working Fluid Components In Cryogenic Systems

Recently with the increasing demand for isotopic materials, the development of customized refrigeration units which allows temperature stabilization, or cryostatting in the temperature range of 30…50 K became necessary. The required temperature stabilization depends on the isotope and process type and need to be performed at different temperatures. Thus, it is obvious that the development of a reliable and efficient refrigeration unit operating in the temperature range of 30…50 K is a relevant objective. This paper presents the result of a preliminary study of the cryogenic system designed for the cold production in the temperature range of 20...50 K. Structurally, the system is designed as a cascade of two refrigeration machines using a mixed refrigerant media as coolant. The Linde-Hampson refrigeration unit, which generates cold at a temperature level of about 90...100 K, is the upper high-temperature stage of the refrigeration cascade. The working fluid of the upper stage is a multicomponent zeotropic mixture of hydrocarbons. The working mixture is compressed in a hermetic lubricated compressor with a moderate compression ratio and a maximum discharge pressure of up to 30 bar. The lower "cryogenic" stage of the system implements the Bell-Coleman cycle. A three-component zeotropic mixture 2H-Ne-He is used as the working fluid of the low-temperature stage, which ensures the operability of the "cryogenic" stage of the system in the temperature range of 20...90 K. The current paper presents the design diagrams and thermodynamic cycles of the system and its elements. The rationale for selection of the refrigerant mixture and a preliminary analysis of the system components are reported.