Exergy-Focused Enhancement Methods for Heat Recovery Steam Generators on the Performance of Combined Cycle Power Plants: A Review

Abstract

Combined-cycle power plants (CCPPs) use a Brayton-Rankine combined cycle, achieving high efficiency through integration of the Brayton and Rankine cycles via an HRSG. This review paper presents a unified thermodynamic comparison of energy- and exergy-based performance for four HRSG configurations: a single-pressure HRSG, a dual-pressure HRSG, a triple-pressure HRSG, and a triple-pressure HRSG with reheat. From the literature, exergy destruction in the combustion chamber was found to be the highest, ranging from 58% to 74%. In the heat recovery steam generator, the high-pressure evaporator contributes the most to heat loss, reaching as high as 40–50%. The efficiency of single-pressure systems is moderate (~41–45%), while dual-pressure systems recover approximately 47–49% of exergy. The triple-pressure reheat configuration offers the best performance, with efficiencies of 60-64% and exergy efficiencies above 54%. Irreversibility is strongly influenced by key parameters, including the pinch point, approach temperature, HRSG pressure levels, supplementary firing, and ambient conditions. Past research has lacked a comprehensive comparison and integrated analysis of design variables, which the current study addresses by identifying the most effective engineering practices to optimize CCPPs for high efficiency and low emissions.