The Phenomenological Theory of Liquid Helium II

Abstract
The purpose of the present paper is to refine the "two-fluid model" as a phenomenological theory of liquid He II. General thermohydrodynamical equations are formulated in Part I, following the treatment of viscous fluids by Eckart and Tolman. The previous phenomenological theories, which have been proposed by Landau, Tisza, F. London and Zilsel, and Gorter, are included in the present general formalism, and their intrinsic relations are discussed from a unified point of view.