Development of a −186 °C cryogenic preservation chamber based on a dual mixed-gases Joule–Thomson refrigeration cycle

First of all, a dual mixed-gases Joule–Thomson refrigeration system was designed, constructed and tested in this work. A minimum no-load temperature of −197.7 °C (about 75.5 K) was reached and about 110 W cooling capacities at −174 °C (about 99 K) was obtained with the mixed-gases refrigeration prototype. Secondly, a cryogenic chamber for biomaterials preservation was built and tested with the similar cycle configuration, which has reached the lowest temperature of −192 °C (about 81 K) with an effective preservation volume of 80 L. A relatively fast cooling-down rate for this cryogenic chamber was obtained. Specifically, it took 2.5 h to reach −180 °C, and about 5 h to reach −190 °C. The cryogenic chamber shows a good perspective as a substitute for traditionally used liquid nitrogen preservation vessels.