Energy, exergy and parametric analysis of a combined cycle power plant

This paper presents the thermodynamics (energy and exergy) analysis of a power plant using the design data. The plant is a triple pressure combined cycle power plant (CCPP) equipped with reheat facilities. The temperature gradient as well as the exergy destruction were determined across each components of the heat recovery steam generator (HRSG). Among the components of the HRSG high-pressure evaporator experienced a large temperature gradient which accounted for high irreversibility while intermediate-pressure superheater experienced low-temperature change and therefore low irreversibility. Exergy analysis showed that the major source of irreversibility (exergy destruction) in the steam turbine cycle (STC) of the CCPP is the stack followed by the HRSG, turbine, and condenser. The exergetic efficiency of the turbine is the highest in the STC with more than 92% while the exergetic efficiency of the condenser was the lowest one with less than 63%. Parametric analyses were conducted where the effects of some operating parameters on the turbine output, efficiencies, and exergy destruction were investigated. The results indicated that superheat pressure, reheat pressure, and steam quality at the exit of the low-pressure steam turbine significantly affect the output of the turbine and efficiencies.