Exergetic Analysis of Combined Cycle Power Plant With Single Steam Extraction

Abstract

Combined Cycle Power Plant (CCPP) is one of the most efficient systems of energy conversion with different topping and bottoming cycles. One of the acceptable schemes, the combination of Brayton and Rankine Cycle, is analyzed for various design parameters. In the present analysis thermodynamic modelling of a CCPP with single steam extraction from bottoming Rankine Cycle is carried out to study the effect of Inlet Air Temperature (IAT), Cycle Ratio (CR), Turbine Inlet Temperature (TIT), air compressor and gas turbine efficiency on the first and second law efficiency. For parametric analysis computer programming tool Engineering Equation Solver (EES) is used and thermodynamic properties of many fluids and gases are inbuilt function of the software. From the results it is concluded that combustion chamber is the source of highest exergy destruction followed by heat recovery steam generator, gas turbine, air compressor and steam turbine. With increase in TIT, optimum CR is also found to be increased because both the gas turbine efficiency and the gas turbine exhaust temperature are increased for the optimum cycle ratio.

Comparative Study of Different Combined Cycle Power Plant Schemes

“…In literature (Dev et al, 2013a) exergy is defined as maximum possible work potential of a thermal system w.r.t. the ambient environment being considered as the datum state.…”

“…The potential of work is further dependent upon the difference in between system and surrounding. In a system entropy generation is due to heat transfer through finite temperature difference (Dev et al, 2013a), chemical reaction (Dev et al, 2013b), mechanical friction (Dev et al, 2013c), mixing of fluids at different temperature (Dev et al, 2013a) and vibration (Dev et al, 2013b). In a CCPP chemical reaction in between air and fuel takes place in CC.…”

Analysis of Thermal System

“…Due to high temperature of operation predominant pollutant generated by a gas turbine are nitrogen oxides (NO x ) which is further dependent upon the C/H ratio of the fuel [12][13][14]. Higher is the hydrogen content in the fuel more is the water formation during combustion.…”