Switchless Sorption-Compressor Design

Sorption coolers are free of vibrations and EMI, and have the potential of a long lifetime. They are, therefore, an attractive for cooling sensitive optical detector systems in space, as well as in ground applications. Generally, gas-gap heat switches are utilized for reducing the input power in the desorption phase of the compressor sorption cycle. This is specifically required in space applications since the compressor cells are cooled by radiators which are proportional in size to the compressor input power. In terrestrial applications, such as the METIS instrument in the European Extremely Large Telescope, low input powers may not be the major concern. Especially in applications requiring both a high cooling powers and a large number of compressor cells, complexity and cost may become more important. In order to reduce these, we developed an alternative switchless sorption-compressor design using short-pulse heating. A dynamic thermal model was built for evaluating this concept and for optimizing the compressorcell dimensions and operating parameters. This paper describes the design of compressor cells with and without heat switches, related to the METIS cooler. Furthermore, it presents experimental results on a switchless compressor that were used for validating a dynamic model. In the paper, the impact of the switchless compressor design on the METIS cooler configuration is also considered.