Comparison of correlations for predicting thermodynamic properties of ammonia-water mixtures

Tillner-Roth and Friend have presented a new correlation for the thermodyna mic properties of ammonia-water mixtures. In this study, the new correlatio n has been compared to other correlations used in simulations of power cycl es using ammonia-water mixtures as working fluids. The saturation propertie s for mixtures, calculated with the different correlations, have been exami ned at different temperatures and pressures. Available experimental data ha ve been included in the comparison. The variation of the enthalpy with temp erature at different pressures for a mixture has also been compared. The co rrelations have been examined for use in power cycle simulations as well. T he comparison reveals that the new correlation shows a more reasonable beha vior when the critical point of the mixture is approached. At lower tempera tures and pressures, the compared correlations give very similar results. T he differences in the results from the cycle simulations, using different c orrelations, are small but they tend to increase with increasing maximum pr essure in the cycle.