The heat conductivity and viscosity of liquid helium II

Measurements have been made in glass capillary tubes of 52 and 108u diameter, in the temperature range from 1.15 to 2.15 °K. For sufficiently small temperature gradients the thermal resistance is independent of the heat flow and is caused solely by the viscosity of the normal fluid, nn. This viscosity has been calculated from the measured thermal resistance data with the use of the existing entropy values, and the results from the two tubes are in very good agreement except for a small deviation at low temperatures which is attributed to slip. The viscosity at the saturated vapour pressure, when corrected for slip, agrees closely with the results obtained by the rotating cylinder viscometer but does not agree with the oscillating disk experiments. The variation of nn at low temperatures follows the theory of Landau & Khalatnikov if A/k is taken as 8.9 °K, but the measured values of the slip correction are slightly larger than would be expected from the theoretical phonon and roton mean free paths. In the 52 u tube the measurements have been extended up to the solidification pressure so as to give nn as a function of density. Near the lambda line nn increases rapidly with density, but at low temperatures the variation is quite small and it is found that the contribution from the rotons is almost independent of density.