Chapter 236 – 1.8 K Refrigeration Units for the LHC: Performance Assessment of Pre-series Units

Publisher Summary This chapter reviews a 1.8 K refrigeration unit for the Large Hadron Collider (LHC) at CERN. Eight refrigeration units of 2400 W will provide the cooling capacity below 2 K for its superconducting magnets at 1.8 K, each of them coupled to a 4.5 K refrigerator. The two selected vendors have proposed cycles based on centrifugal cold compressors combined with volumetric screw compressors with sub-atmospheric suction, as previously identified by CERN as “reference cycle.” The supply of the series units was linked to successful testing and acceptance of the pre-series temporarily installed in a dedicated test station. The global capacity, the performance of cold compressors, and some process specificities have been thoroughly tested and have been presented in this chapter. Their achieved coefficients of performance (COPs) are in the range of 900 W/W with cold compressor isentropic efficiency higher than 70 % for all modes and warm compressor isothermal efficiency around 45 % in sub-atmospheric conditions. Series units delivery at CERN are now finalized for IHI–Linde and are expected in the coming months for Air Liquide allowing then the acceptance tests of the series units.