A mixed-gas miniature Joule–Thomson cooling system

• Published in: Cryogenics (Guildford) 2013-10, Vol.57, p.26-30
• Main Authors: Derking, J.H., Vermeer, C.H., Tirolien, T., Crook, M.R., ter Brake, H.J.M.
• Format: Article
• Language: English
• Subjects: Compressors; Cooling; Cooling systems; Gas cooler; Joule–Thomson; Mathematical analysis; Methane; Micromachining; Miniature; Miniaturization; Mixed-refrigerants; Optimization; Pressure ratio
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2013.04.004

•A mixed-gas Joule–Thomson cooling system cooling down to below 130K is investigated.•A micromachined Joule–Thomson cold stage is combined with a linear compressor.•Operating with a ternary gas mixture, a cooling power of 46mW at 150K is obtained.•The linear compressor can be used to drive 19 of these cold stages in parallel. A mixed-gas Joule–Thomson (JT) cooling system is investigated in which a micromachined JT cold stage of 60×10×0.7mm3 is combined with a linear compressor. The cooling system is operated between 1.3bar and 9.4bar with a ternary gas mixture of 39mol% methane, 20mol% ethane and 41mol% isobutane. It cools down to below 130K, and at a cold-tip temperature of 150K, a cooling power of 46mW is obtained at a mass-flow rate of 1.35mgs−1. The background losses are experimentally determined to be 20mW and are in good agreement with the calculated value of 21mW. The linear compressor can be used to drive 19 of these miniature JT cold stages in parallel, e.g. for cooling optical detectors in future space missions. In this mode, the compressor pressure ratio is slightly less, resulting in a net cooling power of 23mW per miniature JT cold stage.