Performance Analysis of an Integrated Micro Cryogenic Cooler and Miniature Compressor for Cooling to 200 K

Abstract

JouleThomson (JT) based micro cryogenic coolers (MCCs) are attractive because they can provide the cryogenic temperatures needed for small electronic devices while having a low cost and small volumetric footprint. A compressor is a major part of a cryogenic system, but so far JT based MCCs have not used miniature or microscale compressors. This work demonstrates a JT based MCC coupled with a miniature compressor for cooling to 200 K, with precooling of 273 K, using a custom hydrocarbon mixture as refrigerant. The compressor is formed by coupling a miniature piston oscillator built for stirling coolers with a micromachined check valve assembly. The MCC is formed by glass fibers within a capillary forming a counter flow heat exchanger, and a silicon and glass chip forming a JT valve. Minimum temperatures of 166 K have been observed in transient, and stable temperatures of 200 آ±1 K have been observed for >1 h. Some insight is given into the unstable performance in terms of intermittent liquid accumulation. The coefficient of performance is analyzed for the system, and it is found that most of the inefficiencies arise at the compressor.