MEMS-Fabricated, Highly Effective, Compact Recuperative Heat Exchanger for a Miniature, Reliable Cryocooler

RTI will demonstrate the MEMS technologies for a recuperative heat exchanger for a reverse turbo Brayton cycle (RTBC) cryocooler. In the phase I efforts, the heat exchanger would be designed for a 20 W (cooling load), 77K RTBC cryocooler. Selection of this relatively high-temperature cycle is for ease of testing in Phase II, which will involve fabrication of complete cryocooler, testing of the heat exchanger(s) built in Phase I as well as extending the design to lower temperatures down to 10 K. Key technical innovation is based on techniques to drastically minimize performance-degrading axial conduction, while not impeding heat exchange between the hot and cold streams. Microfabrication is a key enabler for implementation of this concept. Multiple fabrication alternatives would be considered. Based on preliminary analysis, the heat exchanger for Phase I is expected to be approximately 3x3x7.5 cm in linear dimensions, weigh about 0.085 kg, and have an effectiveness of 0.982 and a pressure drop of about 1000 Pa in each fluid for a mass flow rate of 0.00181 kg/s of Neon in each side of the heat exchanger, providing an overall COP of 0.083 for a 77 K cooler.