Fast cooling miniature Joule-Thomson cryocooler with improvement of energy recovery and thermal mass distribution

Abstract

Open-cycle conical miniature J-T cryocoolers are favored for applications in the infrared detection field, due to their fast cooling and compact lightweight features. In this type of cryocooler, the regenerative heat exchanger for energy recovery plays a vital role in both its miniaturization and fast cool-down, because its geometry greatly determines the distribution of its heat transfer area and thermal mass. To examine and optimize the effects of the geometry on its fast-cooling performance, a validated transient analysis model, being capable of simulating the entire operating process of an open-cycle miniature J-T cryocooler, was applied to analyze and compared the transient heat transfer and flow characteristics, and then the cooling performance under different operating conditions for one cylindrical and three different cone-angle J-T cryocoolers in this study. Researches show that in terms of geometry, it is advisable to increase the heat transfer area near the cold end of heat exchanger while ensuring a relatively small thermal mass for the entire cryocooler. By analysis, a novel structure of heat exchanger with reduced volume and mass was proposed to enhance the fast-cooling performance and miniaturize cryocooler. Studied results indicate that the performance of this novel cryocooler is improved in terms of reducing the cool-down time by 28% and the volume by 50%. Additionally, this optimized structure exhibits excellent fast-cooling performance under broader operating conditions.