Thermodynamic Model of Hydrazine that Accounts for Liquid-Vapor Phase Change

The work carried out to develop a thermodynamic model of hydrazine with the theoretically built-in capability to account for liquid-vapor phase transitions and suited for implementation in two-phase flow solvers is described. After introductory considerations of fluid dynamics aspects and thermodynamic stability, the method of constructing the model based on an assumed state equation p=p(T, v) and of perfect-gas, constant-pressure, specific-heat data available from tables of thermodynamic properties published in the literature is described. The corresponding fundamental relation is given in terms of the Helmholtz potential. Subsequently, the liquid-vapor phase equilibrium is considered and resolved via equations in line with the standard thermodynamic principles of energy minimization or entropy maximization. Aspects of model validation are discussed with respect to the liquid-vapor saturation curve, vaporization enthalpy, density, and constant-pressure specific heat of the liquid phase. A description of other theoretical models published in the literature, together with a comparative analysis of their features relevant to the context of this work, is also included.