14-11U

A low-density gas in the heat-conduction stationary state is considered. By means of the theory of continuous media, corrections to pressure and internal energy are obtained in the phenomenological approach, which are related to the local temperature gradient. It is derived corresponding expressions for compressibilities along and across the heat flux as well as for heat capacities. These results are generalized to the case when the stationary state of the gas is additionally described by temperature gradients of higher orders. The expression for the nonequilibrium entropy is shown to satisfy the second law of thermodynamics.