  Based on the theory of the thermodynamic equilibrium in a system of quantum
vortices in superfluids in the presence of a counterflow, the influence of a
vortex tangle on various thermodynamic phenomena in quantum liquids is studied.
Using the early calculated partition function we study some of the properties
of He II related to counterflow, such as the distribution of vortex loops in
their length, the suppression of the superfluid density $\rho _{s}$ and the
shift $T_{\lambda}$. Good agreement with the early obtained results is a fairly
strong argument in favor of the point of view that the gas of string-like
topological excitations can indeed be considered as a additional kind of
quasi-particles having the inner structure at high temperatures, especially
near the phase transition. The application of the developed formalism to the
theory of quantum turbulence is briefly discussed.
