Exergetic and Exergo-Economical Analyses of a Gas-Steam Combined Cycle System
Guven Gonca, Bülent Güzel
Abstract
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:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mover accent="true"> <m:mrow> <m:mi mathvariant="italic">m</m:mi> </m:mrow> <m:mo>˙</m:mo> </m:mover> </m:mrow> <m:mrow> <m:mi mathvariant="italic">a</m:mi> </m:mrow> </m:msub> </m:math> {\dot{m}_{a}} ), the flow rate of the fuel mass ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mover accent="true"> <m:mrow> <m:mi mathvariant="italic">m</m:mi> </m:mrow> <m:mo>˙</m:mo> </m:mover> </m:mrow> <m:mrow> <m:mi mathvariant="italic">f</m:mi> </m:mrow> </m:msub> </m:math> {\dot{m}_{f}} ), inlet temperature of the air into the compressor ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mi mathvariant="normal">T</m:mi> </m:mrow> <m:mrow> <m:mn>1</m:mn> </m:mrow> </m:msub> </m:math> {\mathrm{T}_{1}} ), steam temperature ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:msub> <m:mrow> <m:mi mathvariant="normal">T</m:mi> </m:mrow> <m:mrow> <m:mn>6</m:mn> </m:mrow> </m:msub> </m:math> {\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.