Sorption cooling: a valid extension to passive cooling

Abstract

Passive cooling has shown to be a very dependable cryogenic cooling method for space missions. Several missions employ passive radiators to cool down their delicate sensor systems for many years, without consuming power, without exporting vibrations or producing electromagnetic interference. So for a number of applications, passive cooling is a good choice. At lower temperatures, the passive coolers run into limitations that prohibit accommodation on a spacecraft. The approach to this issue has been to find a technology able to supplement passive cooling for lower temperatures, which maintains as much as possible of the advantages of passive coolers. Sorption cooling employs a closed cycle Joule-Thomson expansion process to achieve the cooling effect. Sorption cells perform the compression phase in this cycle. At a low temperature and pressure, these cells adsorb the working fluid. At a higher temperature they desorb the fluid and thus produce a high-pressure flow to the expander in the cold stage. The sorption process selected for this application is of the physical type, which is completely reversible. It does not suffer from degradation as is the case with chemical sorption of, e.g., hydrogen in metal hydrides. Sorption coolers include no moving parts except for some check valves, they export neither mechanical vibrations nor electromagnetic interference, and are potentially very dependable due to their simplicity. The required cooling temperature determines the type of working fluid to be applied. Sorption coolers can be used in conjunction with passive cooling for heat rejection at different levels. This paper starts with a brief discussion on applications of passive coolers in different types of orbits and on the limitations of passive cooling for lower cooling temperatures. Next, the working principle of sorption cooling is summarized. The DARWIN mission is chosen as an example application of sorption and passive cooling and special attention is paid to the reduction of the radiator area needed by the sorption cooler. The application field of this type of sorption cooling in space missions is currently being expanded by examining the performance of alternative working fluids, suitable for different cooling temperatures.

Performance comparison of sorption compressors for methane using metal-organic frameworks and activated carbon as adsorbents

“…Cryocoolers combined with mechanical compressors still induce microvibration, although active and/or passive isolation techniques have been employed [2]. By employing heat rather than mechanical work, sorption cryocoolers are attractive for cooling optical sensors because of their advantages of no oil, no vibration (except for several check valves), no electromagnetic interference, high reliability and long lifetime [3].…”

Experimental studies on a metal hydride–based single bed sorption cryocooler

“…Lower temperature developments have widely increased within industries and the laboratories and the cryocoolers reality includes an expansive number of providers . Sorption cryocoolers are used to produce a continuous cooling effect and work based on hydrogen compression, precooling of gas by heat exchangers, expansion of gas in J‐T valves and further evaporation in the evaporator . Sorption compressors are used in space applications as motors are not allowed in space.…”