Performance characterization of a 20 K, High-Capacity cryocooler for Cryo Fluid Management

Future NASA mission architectures for travel to and habitation of the Lunar and Martian surfaces will require the capability of zero-boil-off storage and liquefaction of hydrogen. To intercept the projected heat loads on the cryogen tanks or to liquefy, a high capacity cryocooler providing refrigeration at 20 K is required. In addition to the refrigeration requirements, high overall efficiency is required to remain within overall size and power constraints. Creare developed and recently demonstrated a high-capacity turbo-Brayton cryocooler to meet these requirements and to support future NASA mission initiatives. The cryocooler is a single-stage turbo-Brayton cryocooler designed to produce 20 W of refrigeration at 20 K and reject heat at 270–300 K. Thermodynamic characterization testing demonstrated up to 22.5 W of refrigeration at 22.7 K and up to 21.4 W of refrigeration at 20 K. The maximum cryocooler COP was 16 % of the Carnot cycle at a 285 K heat rejection temperature and the minimum specific power was 80 W/W. The cooling capacity and performance of this cryocooler are new benchmarks for 20 K cryocoolers for space. This paper reviews the thermodynamic performance characterization testing of the cryocooler.