Concept for thermal insulation arrangement within a flexible cryostat for HTS power cables

摘要

The successful application of high temperature superconducting power cables requires improved flexible cryostats with respect to their thermal heat load between environment (300 K) and LN_2 (77 K) operating temperature. Heat transfer through the thermal radiation consists of thermal radiation, solid and residual gas conduction. Considering this heat load contributions, a new concept for the thermal insulation arrangement is presented in this paper. The main advantage of this concept consists in a separation of the thermal insulation and the supporting structure. This separation protects the thermal insulation rum degradation by mechanical load. The fraction of solid heat conduction through this support structure is minimised by small contact areas and high heat conduction lengths. Heat transfer due to residual gas conduction is reduced by improved evacuation conditions close to the cold wall. Finally the structure allows subdivision of the multilayer insulation ensuring an optimal number of layers with respect to their insulation thickness, i.e. an optimal layer density.