Energy and exergy analysis of steam cooled reheat gas–steam combined cycle

This paper deals with parametric energy and exergy analysis of reheat gas–steam combined cycle using closed-loop-steam-cooling. Of the blade cooling techniques, closed-loop-steam-cooling has been found to be superior to air-film cooling. The reheat gas–steam combined cycle plant with closed-loop-steam-cooling exhibits enhanced thermal efficiency (around 62%) and plant specific work as compared to basic steam–gas combined cycle with air-film cooling as well as closed-loop-steam cooling. Further, with closed-loop-steam-cooling, the plant efficiency, reaches an optimum value in higher range of compressor pressure ratio as compared to that in film air-cooling. It has also been concluded that reheat pressure is an important design parameter and its optimum value gives maximum plant efficiency. Component-wise inefficiencies of steam cooled-reheat gas–steam combined cycle based on the second-law-model (exergy analysis) have been found to be the maximum in combustion-chamber (≈30%), followed by that in gas turbine (≈4%).