Measurements of heat transfer to helium II at atmospheric pressure in a confined geometry

The enhanced heat removal capability of unsaturated superfluid helium 2 as used in fusion and accelerator dipole magnets was investigated. In superfluid the internal convection mechanism dominates the heat removal process and orientation with respect to gravity becomes of secondary importance. Heat transfer, can be influenced by the thermodynamic state of the liquid, especially with regard to possible phase transformations. The transformation from nonsaturated He 2 must involve an He 1 state before the film boiling transition is experienced. The attenuation of heat transfer within the restrictive geometry of typical magnet designs was measured. Cooling passages between turns result from gaps between the electrical insulation, and are typically on the order of a fraction of a millimeter.