Axial transfers tube heat leak of rotating superconducting machines: Fluid contribution

Experiments have been conducted to measure the heat leak of a transfer tube assembly (rotating cylinder/stationary cylinder) in the fluid - filled gap at the low temperature end in axial direction. The angular frequency was varied up to 300 rad/s. Fluid He⁴, pressurized above its thermodynamic critical pressure was used to eliminate two - phase conditions. Zero net mass flow was established. The variation of the heat leak QLwith the gap width s was found to be .