Operational analysis and update on modifications to a helium liquefier under development at BARC

An experimental helium refrigerator/liquefier is being designed and developed by Cryo-Technology Division to be installed at Bhabha Atomic Research Centre, Mumbai. During first trial runs, certain limitations of the process were observed and some other fabrication/development issues came to light. After detailed steady state cycle simulation studies, it was decided to undertake some major modifications to achieve the target of about 200W refrigeration capacity at around 4.7K. The most significant modification involved changing the basic thermodynamic cycle from Collins to a modified Claude cycle which is more suited to turboexpanders. To this effect, simulation studies on the new cycle, with two turboexpanders in series interspaced with a multi stream heat exchanger, was taken up and the process computed. The present paper aims to describe in details different studies taken up on the helium refrigerator. It also aims to provide an update on the present status of development of the helium refrigerator/liquefier.