Improvement of Helium Liquefaction Performance Based on the Temperature-Distributed Regenerative Refrigeration Method Using 3He Fluid

Abstract

Liquid helium has important applications in infrared wavelength detection, superconducting quantum interference, and so on. Regenerative refrigerators are generally applied for small-scale applications. However, the liquefaction efficiency of helium is not high. The main reason is the contradiction between the large sensible heat load and the limited refrigeration efficiency at 4.2 K. A novel method of temperature-distributed regenerative refrigeration, which generates the refrigeration power over a wide temperature range based on real gas effects, is theoretically studied using the ³He working fluid for the first time. The liquefaction rate and efficiency of helium is improved because of a smaller entropy generation with this temperature-distributed method. The temperature-distributed refrigeration power of the ³He working fluid is larger than that of ⁴He when the absolute pressure is smaller, because the critical pressure of ³He is lower; while such a refrigeration power of ³He distributes at a lower temperature range that of ⁴He at the same reduced pressure because the critical temperature of ³He is lower. The liquefaction rate reaches 50.5 L/d when the cold-end refrigeration power is 1.5 W. This rate is 2–3 times that of liquefying with only the cold end with ⁴He or ³He. Furthermore, the liquefaction efficiency (FOM) increases with the rise in pressure. The theoretical FOM is 47.7% at a reduced pressure of 61.7 (14.1 MPa), which is a 7% improvement over the case with ⁴He (44.7%). These results demonstrate advantages of using the temperature-distributed method with ³He, thus opening up a new avenue for further researches in helium liquefaction systems.