Exergetic and Exergo-Economical Analyses of a Gas-Steam Combined Cycle System

Abstract In this study, the results of an investigation of the performance of a gas-steam combined cycle system (GSCCS) under exergetic and exergo-economical criteria are reported. The effective power (P ef ), destroyed exergy (X), efficiency of exergy (ε), unit electric generation cost (C elec ) and exergy-dependent economic worth of electrical energy (C ex,elec ), which is novelly determined in this study, have been analyzed. The impacts of speed ( N ), pressure ratio of the gas cycle (λ), equivalence ratio (ϕ), the flow rate of the air mass ( m ˙ a {\dot{m}_{a}} ), the flow rate of the fuel mass ( m ˙ f {\dot{m}_{f}} ), inlet temperature of the air into the compressor ( T 1 {\mathrm{T}_{1}} ), steam temperature ( T 6 {\mathrm{T}_{6}} ) and pressure (P 6 ) of the heat exchanger, outlet pressure (P 7 ) of the high pressure steam turbine and condenser pressure (P 9 ) on P ef , ε, C elec and C ex,elec have been parametrically evaluated. It was revealed that the stream and component characteristics of the system have significant influences on the performance characteristics of the GSCCS.