DESCRIPTION OF THE REAL-GAS ISENTROPIC CHANGES FOR AN AMMONIA-WATER VAPOR MIXTURE

The NH3-H2O binary mixture is used extensively in industrial refrigera tion or heat-pump applications while it is a candidate for future unit s working with resorption-compression [1]. In this paper, the thermody namic changes of an ammonia-water mixture in the vapor phase, along an isentropic expansion, have been calculated numerically for a starting point with a temperature of 800 degrees C and initial pressures of 20 , 30, 40, and 50 bar. For this purpose, a special computer program, IS ENEXPR, has been developed. The thermodynamic relations used were obta ined in terms of the Gibbs free energy equation for the gas phase of p ure components [1], [3], [6] and the entropy was held constant with an accuracy better than 0.000001 kJ/kgK. The runs performed for isentrop ic expansions showed a dependence of the isentropic on the both expone nts initial pressure and NH3 mass fraction xi, while the other propert ies depend on varying degrees upon xi. Results are given in the form o f diagrams, describing the isentropic change of the NH3-H2O gas phase mixture.