JPS6414560A - Cryogenic refrigerating machine - Google Patents

Abstract

PURPOSE: To decrease the size and the number of units by precooling refrigerant gas helium through a Gifford-MacMahon chiller and then cooling the refrigerant through a Joule-Thomson heat exchanger and expanding through a Joule- Thomson valve thereby attaining cryogenic temperature. CONSTITUTION: Pressurized refrigerant helium gas compressed through a compressor 22 is fed to a precooling chiller 26 after impurities are removed therefrom and then passed through first and second cold stages 29a, 29b where the pressure is dropped down to about 8 atm before the majority of refrigerant helium gas is returned back to the compressor 22 through a low pressure outlet 27b. On the other hand, gas helium branched from the forward end and the temperature is lowered down to about 20 deg.K by a capillary 30 is fed through a Joule-Thomson heat exchanger 33 through a surge tank 32. The refrigerant is heat exchanged thereat with low pressure low temperature gas helium and cooled down to about 10 deg.K and fed to a cryogenic temperature generating section 35 where it is subjected to Joule-Thomson expansion thus generating chill of about 4 deg.K. Subsequently, it is returned back to the compressor 22 white raising the temperature sequentially by robbing heat from the section 35, and the heat exchanger 33, and heat exchanging sections 36b, 36a.