Helium II thermal counterflow: Temperature- and pressure-difference data and analysis in terms of the Vinen theory

An extensive investigation of the temperature and pressure difference associated with the thermal counterflow of He II in long capillary tubes is reported. For heat currents that are not too large, our temperature data are in excellent agreement with the Vinen theory in which mutual friction is regarded as arising from a homogeneous mass of quantized vortex line. Our pressure data, which are obtained simultaneously with the temperature data, are used to determine the eddy viscosity of the vortex lines. The Vinen theory is reviewed and somewhat modified in the light of these and other recent results. It is suggested that the vortex-line model of thermal counterflow is one of the few successful quantitative models of nonlinear hydrodynamics effects in He II