The study of 4He twin-tube convective heat switches

Abstract

In many cryogenic experiments and applications, there is a requirement for a heat switch. The heat switch can be used to either control the thermodynamic cycle or increase the cool-down speed. Here a twin-tube convective switch, which is essentially a closed circuit comprising stainless-steel twin-tube and copper heat exchangers connected to the cold-end (4 K) and warm-end (40 K), is numerically studied for the purpose of increasing the cool-down speed. The numerical results are validated by the experimental study. The geometric parameters and structures have significant impact on its performance. The performance analysis in terms of heat flow through the switch are conducted. Based on the parametric simulation results, the structure of the heat switch is further investigated. The heat flow of the heat switch with vertical fin-structure is 6.02 W, which is 2.7 times higher than that of the experimental case with a cylindrical cavity, which highlights the need to improve overall cool-down speed of the system.