  We investigate the transport properties of a kinetic theory model that is
tuned to describe the thermodynamic properties of QCD at zero chemical
potential using a new formulation of the relaxation time approximation. In
contrast to previous approaches, the latter is constructed to preserve the
fundamental properties of the collision term of the Boltzmann equation for any
energy-dependence of the relaxation time. A novel choice of matching conditions
is implemented to ensure that the background mean-field depends only on the
temperature even when the system is out of equilibrium. We provide a consistent
analysis of how the transport coefficients of relativistic Navier-Stokes theory
vary with the energy dependence of the relaxation time. We also show that the
entropy production of this theory is consistent with the second law of
thermodynamics and verify that it is independent of the matching conditions
employed. We used this fact to calculate the matching independent combination
of transport coefficients.
