Novel concept of 60-120 kW at 4 K refrigerator

Abstract

In the last 50 years several new large cryogenic facilities with capacities up to 150 kW at 4 K were taken in operation. This required development of new generation of refrigerators/liquefiers with capacities ranges 18-25 kW at 4 K. In order to cover the required cryogenic load, several cryogenic groups, e.g. at CERN, ITER, JLab, SLAC, have to install several refrigerators with maximal power capacities each. As an alternative, development of larger refrigerators up to 120 kW power could be an alternative to the installation of several “small” ones. In the present paper, the novel concept of 60-120 kW refrigerator is considered. The discussion of novel concept will be preceded by discussion of basic design of current “state-of-the-art” refrigerators/liquefiers as well as advanced ones using high efficient heat exchangers and turbines with expected overall thermodynamic efficiencies up to 35%. For the “state-of-the-art” design, we tried to use the standard and already proven technologies in as many as possible cases, though resent developments are also considered. In practice, the refrigerators/liquefiers are designed for the specific load, e.g. pure refrigerator, pure liquefier or somehow in between these limits; however, as the cryogenic heat load for future cryogenic facilities could be different, we tried to apply general process schemes, which could be suitable to refrigerator/liquefier working at 4 K temperature level. The general layouts, screw/turbo compressor stations, 80-300 K as well as 4-80 K boxes are considered. For the advanced design, similar components are used; however turbine and heat exchangers efficiencies are in the range of 82-85% and ca. 98%, respectively. For the novel concept, the applications of turbo compressors as well as several new process schemes of 4 K boxes are considered.