Non-linear extended thermodynamics of real gases with 6 fields

We establish extended thermodynamics (ET) of real gases with 6 independent fields, i.e., the mass density, the velocity, the temperature and the dynamic pressure, without adopting the near-equilibrium approximation. We prove its compatibility with the universal principles (the entropy principle, the Galilean invariance and the stability), and obtain the symmetric hyperbolic system with respect to the main field. In near-equilibrium we recover the previous results. The correspondence between the ET 6-field theory and Meixner׳s theory of relaxation processes is discovered. The internal variable and the non-equilibrium temperature in Meixner׳s theory are expressed in terms of the quantities of the ET 6-field theory, in particular, the dynamic pressure. As an example, we present the cases of a rarefied polyatomic gas and study the monatomic-gas limit where the system converges to the Euler system of a perfect fluid.