Thermal mass and thermal inertia in fluids - A comparison of hypotheses
Stanisław Sieniutycz , R. Stephen Berry
AbstractThermal inertia and thermal mass are concepts that offer means to describe transport of heat in nonequilibrium fluids. However there are options regarding how to separate the part of the total flow that caries entropy from the "mechanical", nonentropy-bearing part. Some hypotheses are examined and compared for constructing such a field theory of thermal mass in the energy representation. A global intrinsic symmetry and a finite thermal momentum imply that any formulation which hypothesizes a constant ratio θ of thermal mass to the entropy must tie the thermal mass to the so-called bare mass of particles, to preserve the global conservation of matter. However, in any formulation consistent with the Grad-Boltzmann theory, where θ must be variable, the thermal mass behaves as a separate variable governed by the entropy and the second law. Nonetheless, in this case θ has a reasonably broad plateau of values within which entropy is a measure of the thermal mass associated with changes of state. Nonlinear transformations linking usual thermodynamic variables with those of the thermal mass frame preserve the components of the tensor of matter, including Nöther's energy and pressure. A formula is given for the fraction of the observed mass assignable as thermal mass, in accordance with Grad's solution of the Boltzmann equation.
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