Thermodynamic Analysis of Supercritical and Subcritical Rankine Cycles

In this work the thermodynamic analysis of two power cycles operating at ultracritical and supercritical conditions (300 bar, 600°C), and conventional or subcritical (124 bar, 538°C) is made. The supercritical cycle has ten and eight stages of regenerative feed heating. The conventional cycle has seven and six stages of regenerative feed heating. The aim of this analysis is to show the variation of work out, thermal efficiency, the heat rate, specific steam and fuel consumptions and the operating range of the pressure of overheating. For example, supercritical conditions operation of 300 bar and 600°C and a condensation pressure of 0.1107 bar, the maximum pressure reheating is 100 bar, because with a higher pressure, steam quality at the end of the step of expanding the low pressure turbine will be less than 0.88, requiring a second reheating. Additionally, the supercritical Rankine cycles have better thermal efficiency than subcritical cycles, increases in average 6%, and consequently the heat rate and steam and fuel consumption decrease.© 2016 ASME