The thermal efficiency of a pumped supercritical helium helium refrgeration system operating below 6 K

Abstract The thermal efficiency of a pumped supercritical helium refrigeration system is calculated as a function of the heat load operating temperature and the supercritical helium pressure. The increase in the compressor power requirement caused by the pump operation over the compressor power required for a 4.5 K liquid helium refrigerator is presented. The use of reciprocating pumps is favoured over a centrifugal pump because of lower losses and its capability to operate at higher temperature during cool-down.