The study of active gas-gap heat switch using carbon nanotubes as the adsorption material

Abstract

Heat switches are widely used in cryogenic systems and play an important role in controlling thermodynamic cycles and accelerating the cooling of cryogenic components, etc. Among them, the active gas-gap heat switch, as one of the mainstream heat switches, mostly uses activated carbon as the adsorbent. It desorbs/adsorbs helium by heating/cooling the activated carbon to realize the ON/OFF state. Normally, a short response time, which is related to the adsorption properties of the materials and the heating method of the adsorption bed, is desired. In order to further shorten the response time and improve the performance of the heat switch, a 3He active gas-gap heat switch using carbon nanotubes as the adsorption material was investigated. About 0.06 mW/K OFF-state conductance and 60 mW/K ON-state conductance were obtained at 4 K. The heat switch switched on within 35 s when 1.6 mW heating power was applied to the adsorption bed, and it took about 400 s at 4 K to reduce thermal conductance to 1/10 of ON-state conductance when the heating of the adsorption bed was stopped.