Progress in Joule-Thomson Microcooling at the University of Twente

Abstract

The development of miniaturized Joule-Thomson (JT) coolers has been an ongoing research topic at the University of Twente for many years. In the current research, a new run of singlestage JT microcoolers with gross cooling powers of 40 mW and 180 mW at 100 K was developed and fabricated. The temperature profiles along the counter-flow heat exchangers of both types were measured, as were their net cooling powers. Operated with nitrogen gas, the latter was measured to be 26 mW at 90 bar and 131 mW at 80 bar, for both types, respectively. Furthermore, it is shown that the influence of gravity on the performance of the microcoolers is negligible. Also, the issue of clogging caused by tiny amounts of water is further investigated. No clogging is observed when the microcooler is driven by gas cleaned with a microtorr® getter filter. However, when unpurified gas is used, clogging occurs during cool down and prevents the microcooler from cooling down below about 230 K. Furthermore, the incorporation of sorption compressors is explored to make a closed-cycle JT microcooler that delivers 50 mW at 100 K. A final design is made on the basis of a quasistatic thermodynamic analysis. The cooler will operate with methane as the working fluid, and the total input power will be around 33 W.