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

Abstract

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 ow solvers is described. After introductory considerations of uid 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, speci c-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 speci c 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. Nomenclature A; B; C; n = state equation constants a k = interpolation coef cients, Eq. (26) a N = isothermal speed of sound c p = constant-pressurespeci c heat c v = constant-volumespeci c heat f = Helmholtz potential h = enthalpy K T = isothermal compressibility coef cient K 1 ; K 2 = integration constants M = N 2 H 4 molar mass, 32.045282£ 10 ¡3 kg ¢ mol ¡1 p = thermodynamic pressure R = hydrazine gas constant, 259.46 Jand maximum reduced pressure ½ = mass density ¿ = reduced temperature ¿ t = tangent-isothermreduced temperature 8.T / = perfect-gas constant-volume speci c heat Á = reduced speci c volume ' = reduced shifted speci c volume ' m ; ' M = left and right limits of unstable-state ranges ' np;l ; ' np;r = left and right limits of negative-pressureranges à .T / = generic function of temperature Subscripts c = critical l = saturated liquid v = saturated vapor vap = vaporization

Advances in Hypergolic Propellants: Ignition, Hydrazine, and Hydrogen Peroxide Research

“…This modified Claussius equation model correctly predicts the hydrazine liquid-vapor phase equilibrium from 273.15 K to the critical point as well as capturing the low-density behavior of hydrazine (as an ideal gas). However, the model does not correctly predict the constant pressure heat capacity ( ) of hydrazine; this suggests changes to the state equation in later studies will be necessary [14].…”

“…However, before a valid model can be developed to explain the reaction from liquid hydrazine to gaseous combustion products, a detailed understanding of the thermodynamics of hydrazine is first required. In 2002, a model based on the Claussius equation and the Helmholtz potential was developed in order to accurately predict the liquid-vapor phase changes of hydrazine [14]. This modified Claussius equation model correctly predicts the hydrazine liquid-vapor phase equilibrium from 273.15 K to the critical point as well as capturing the low-density behavior of hydrazine (as an ideal gas).…”

Experimental study of the Ariane 5 attitude control system (SCA) passivation

“…The present work is limited to the experimental part of that program. The other parts are presented elsewhere [4], [5], [6].…”