Experimental study on a simplified precooled JT cryocooler for liquid hydrogen zero boil-off storage

For a hydrogen zero boil-off storage system in space, active cooling technique is one of the key technologies that requires effective cryocoolers. The precooled Joule-Thomson (JT) cryocooler working at liquid hydrogen tem-perature has no moving parts at low temperature with continuous refrigeration, making it reliable for space applications. In this study, a new simplified JT cryocooler with a large cooling capacity is proposed to approach liquid hydrogen refrigeration. In order to clarify cooling capacity characteristics of the simplified JT cryocooler, a laboratory prototype precooled by a Gifford-Mcmahon (GM) cryocooler is designed, fabricated and tested. The cool-down process of the simplified JT cryocooler is presented. A stable cooling capacity of 10.06 W at 20.7 K is provided by the cryocooler. The availability of the simplified JT cryocooler without a bypass assembly is verified.