Design parameters for cryogenic thermosyphons

Abstract

Cryogenic thermosyphons are the thermal conductors of choice for a variety of applications such as conduction-cooled superconducting devices. They exhibit a small effective thermal resistance at small cross-sections. A careful design, however, is crucial to ensure sufficient heat transport for all possible heatloads. The aim of this work is to obtain experimental results on critical limitations and the effective thermal conductivity dependent on the length, the cross-sectional area, and the working liquid fill level of a thermosyphon for different heatloads. For the experiments, a modular thermosyphon was designed with 5 different adiabatic tubes of length [cm]/cross-sectional diameter [cm] 10/1, 10/2, 30/0.5, 30/1, 30/2, which can be mounted between condenser and evaporator. The thermosyphon was operated with different fill levels of either nitrogen or neon and different heatloads. The effective thermal conductivity between condenser and evaporator was determined, dependent on the design parameters mentioned above. Additionally, the useful temperature range of operation was determined, and limitations were monitored and visualized using a built-in camera. The results can support the proper design of thermosyphons for dedicated applications by providing information about the heat transport capability for different thermosyphon design parameters. © 2008 American Institute of Physics.