Abstract
Measurements have been made of the heat transfer in liquid helium II in a capillary glass tube with an inside diameter of 93.3μm and a length of 8.5cm. Heat supplied to a lower part of a cell produced a thermal counterflow in the tube. The temperature difference (ΔT) across the tube was measured using a thermocouple (Au [0.03 at% Fe]-Nb⋅Ti) with a SQUID detector. The obtained value of the critical vortex line density (L0)c associated with the transition from a turbulent flow to a laminar flow was larger than that given by Vinen.
The spontaneous periodic fluctuation (ΔTf) of the temperature difference was observed at the transition. The period of the fluctuation was about 20 seconds and the magnitude of ΔTf/ΔT was about 0.15 at 1.5K.
