Thermophysical properties of ammonia-water mixtures for prediction of heat transfer areas in power cycles

In power cycles using ammonia-water mixtures as the working fluid, several heat exchangers are used. The influence of different correlations for predicting thermophysical properties on the calculations of the size of the heat exchangers is presented. Different correlations for predicting both the thermodynamic and the transport properties are included. The use of different correlations for the thermodynamic properties gives a difference in the total heal exchanger area of 7%, but for individual heat exchanges, the difference is up to 24%. Different correlations for the mixture transport properties give differences in the predicted heat exchanger areas that are, at most, about 10%, for the individual heat exchangers. The influence on the total heat exchanger area is not larger than 3%. A difference in the total heat exchanger area of 7% would probably correspond to less than 2% of the total cost for the process equipment. Experimental data and correlations developed for the ammonia-water mixture transport propel ties are very scarce. The evaporation and condensation processes involving ammonia-water mixtures are also not fully understood.