High-Heat-Flux Regime of Superfluid Cooling in Vertical Channels

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Abstract
Limiting temperature gradients at the breakdown of superfluid heat transport have been measured as a function of temperature for three configurations of insulated vertical channels. Values of the temperature gradient calculated from a vaporization hypothesis are in good agreement with the experimentally measured gradients, indicating that metastable superheating does not occur. Systematic discrepancies noted at low temperatures and high heat fluxes show that the vaporization hypothesis is not a complete description. Values of the Gorter-Mellink constant have been determined and are found to exhibit a systematic dependence on channel size as well as temperature. Limiting heat fluxes calculated using the experimentally determined Gorter-Mellink constant are in good agreement with experimental values above ∼ 1.6 K; deviations are observed at lower temperatures.