Experimental study on a closed-cycle Joule-Thomson cryocooler working at liquid hydrogen temperature

Because of high reliability, simplicity and no moving parts in the cold end, the Joule-Thomson (JT) cryocooler working at liquid hydrogen temperature has the potential to be used in the field of hydrogen liquefaction, liquid hydrogen storage and electronic devices cooling. However, studies on JT cryocoolers with cooling capacities above 10 W at liquid hydrogen temperature are rare. Therefore, in order to study cooling characteristics of a closed-cycle JT cryocooler working at liquid hydrogen temperature with a cooling capacity above 10 W, a laboratory prototype of a simplified JT cryocooler driven by an oil-lubricated scroll-type compressor has been built and tested. Pure hydrogen gas is used as the working fluid. The cool-down process of this closed-cycle JT cryocooler is illustrated and analyzed. The cooling temperature of 20.7 K is approached at the end of the cooldown process. Using the heat balance method, a stable cooling capacity of 10.9 W at 20.8 K is measured. The stability of temperature, pressure and mass flow rate is analyzed. Over a period of 0.5 h, the maximum differences in cooling temperature and pressure are lower than 0.1 K and 0.001 MPa, respectively. Mass flow rate fluctuation which is 0.44 mg/s has little influence on the cooling temperature.