The role of thermodynamics in deriving constitutive equations is unique, and various approaches have been developed in the last decades. In the present paper, the frameworks of Extended Irreversible Thermodynamics (EIT) and Non-Equilibrium Thermodynamics with Internal Variables (NET-IV) are discussed and compared to each other on the basis of a particular problem of rarefied gases. In this comparison, both theoretical and experimental aspects are taken into account. Eventually, an experiment by Meyer and Sessler covering a wide range of pressures and frequencies is investigated. Here, concentrating on the scaling properties and the density dependence of parameters, the change of speed of sound in terms of frequency and pressure is recovered using NET-IV, and this fitting is compared to the results of Lebon and Cloot using EIT. NET-IV and EIT are seen to be more flexible than Rational Extended Thermodynamics (RET) concerning the functional form of the transport coefficients, which gives them some advantages over RET in some ranges of values of gas density.

热力学在推导本构方程方面的作用是独一无二的，并且在过去几十年中开发了各种方法。在本文中，扩展不可逆热力学 (EIT) 和具有内部变量的非平衡热力学 (NET-IV) 的框架基于稀薄气体的特定问题进行了讨论和比较。在这个比较中，理论和实验方面都被考虑在内。最终，Meyer 和 Sessler 进行了一项涵盖广泛压力和频率的实验。在这里，专注于参数的缩放特性和密度依赖性，使用 NET-IV 恢复了声速在频率和压力方面的变化，并将这种拟合与使用 EIT 的 Lebon 和 Cloot 的结果进行了比较。