Keywords: exergy analysis, energy analysis, ammonia–water combined cycle, exergy destruction, performance, thermodynamic modelling, working fluids, bottoming cycle, ammonia, water
Thermodynamic modelling of three–stage combined cycle power systems utilising ammonia–water mixture as a working fluid in bottoming cycle
In this study, two three–stage combined power cycles with ammonia–water mixture in bottoming cycle are introduced; one with variable ammonia fraction and the other with constant ammonia fraction. Energy and exergy analyses are carried out and optimal parameters of the proposed cycles are compared with the conventional power cycles. The second law efficiency of three–stage cycles with variable and constant ammonia fraction are 4.71% and 5.15% higher than steam–gas combined power cycle, respectively. Exergy flow diagram for each cycle is presented and exergy destruction of all components is investigated. Results quantitatively highlight the thermodynamic advantages of the proposed cycles in comparison with the conventional cycles. Three–stage cycle with constant ammonia fraction has the best performance in comparison with the others.