Abstract
The characteristics of heat transfer in a simulated channel for a large superconducting coil have been investigated. Subcooled He I layer on the heated surface exposed to the pressurized superfluid helium (He IIp) expands the non-boiling region beyond the Kapitza region up to qn, above which nucleate boiling sets in. As the bath temperature decreases, the orientation-independent qn is increased more rapidly than qλ, at which the superfluidity is broken at the center of the heated surface. A decrease in the temperature of the coolant in contact with the heated surface has been detected in He IIp as well as in the saturated He II. Enhanced stabilization can be established for superconducting coils by taking qn into account; the temperature rise at the hot spot on the superconductor may be restrained below 4.5K without bubbling.
