Pool heat transfer to liquid and supercritical helium in high centrifugal acceleration fields

Abstract

In relation to the problem of cooling the rotating field windings of a superconducting alternator, a preliminary experimental study of pool heat transfer to helium under high speed rotation is reported. Heat transfer from a flat copper surface has been measured for a range of heat flux 0.2–650mW cm −2 and in local centrifugal acceleration fields of 180–1720g perpendicular to the surface. Analysis of the data indicates that the mode of heat transfer by free convection at both subcritical and supercritical pressures follows the simple correlation Nu = 0.29 Ra 0.29. At subcritical pressures, nucleate boiling is an additional process at sufficiently high heat fluxes.