A Deeper Look into the Thermodynamic Perfection of the Debye Equation of State for Helium-3

A new form of a state equation for helium-3 in wide range of temperature and pressure, based on a conceptual extrapolation from the Debye equation for specific heat of solid materials was previously developed. A deeper look into the performance of the state equation was recently considered necessary and valuable, due to some feedback from cryogenic applications. The evaluation of has been conducted with the Grüneisen parameter along isobar and isotherms, cubic sound velocity – pressure linearity, enthalpy and entropy at low pressures, and the virial coefficients as the benchmarks. Some similar analysis was applied to helium-4 for the sake of analogizing the common behavior of these isotopes, particularly in the critical region. The results confirmed the good thermodynamic perfection of the Debye state equation for helium-3 in most areas on the phase diagram as declared before.