In general, the superfluid behaviour is modelled through phenomenological
and microscopic theories. In the phenomenological approach,
a superfluid is generally considered a mixture of two fluids, one with
superfluid behaviour and one normal that gradually disappears with a
decreasing temperature [4,5].
Although the second sound is a quantum mechanical phenomenon
in which heat transfer occurs by wave-like motion, the goal of the
present paper is to use basic principles of classical Thermomechanics
of Continuum Media to analyse the effect of the thermomechanical
coupling on the hyperbolic heat transfer in a superfluid undergoing a
complex flow. To make the reasoning clearer, temperature is assumed
to be below critical and only the supercritical fraction of the fluid is
considered. In the framework of Thermomechanics of Continuum
Media, we are not directly interested in the microstructure of the
matter, and the material (continuum like) behaviour is described
through constitutive equations. Therefore, in the analysis, we will not
use statistical methods to predict the thermodynamic properties of a
system from the microscopic structure of its constituents neither will
we consider relativistic heat conduction. The approach is preliminary
but allows understanding how turbulent compressible irrotational
flows caused by the lost of internal friction may affect heat transfer. It
is shown that, due to the thermo-mechanical coupling, density waves
may induce heat sources or sinks travelling at sound speed, while
temperature waves travel at a different and independent speed.
Sufficient conditions for an objective and thermodynamically
consistent modelling of hyperbolic heat transfer in supercritical fluids
are presented and analysed. An objective version of the Cattaneo
equation is adopted. A general procedure, developed within the framework
of thermodynamics of irreversible processes allows presenting
sufficient conditions to satisfy a local version of the second law of
thermodynamics.
In general, the superfluid behaviour is modelled through phenomenological
and microscopic theories. In the phenomenological approach,
a superfluid is generally considered a mixture of two fluids, one with
superfluid behaviour and one normal that gradually disappears with a
decreasing temperature [4,5].
Although the second sound is a quantum mechanical phenomenon
in which heat transfer occurs by wave-like motion, the goal of the
present paper is to use basic principles of classical Thermomechanics
of Continuum Media to analyse the effect of the thermomechanical
coupling on the hyperbolic heat transfer in a superfluid undergoing a
complex flow. To make the reasoning clearer, temperature is assumed
to be below critical and only the supercritical fraction of the fluid is
considered. In the framework of Thermomechanics of Continuum
Media, we are not directly interested in the microstructure of the
matter, and the material (continuum like) behaviour is described
through constitutive equations. Therefore, in the analysis, we will not
use statistical methods to predict the thermodynamic properties of a
system from the microscopic structure of its constituents neither will
we consider relativistic heat conduction. The approach is preliminary
but allows understanding how turbulent compressible irrotational
flows caused by the lost of internal friction may affect heat transfer. It
is shown that, due to the thermo-mechanical coupling, density waves
may induce heat sources or sinks travelling at sound speed, while
temperature waves travel at a different and independent speed.
Sufficient conditions for an objective and thermodynamically
consistent modelling of hyperbolic heat transfer in supercritical fluids
are presented and analysed. An objective version of the Cattaneo
equation is adopted. A general procedure, developed within the framework
of thermodynamics of irreversible processes allows presenting
sufficient conditions to satisfy a local version of the second law of
thermodynamics.
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