Parametric optimization of a combined cycle

For the combined cycle power plants, the optimization of the heat recovery steam generator (HRSG) is of particular interest in order to improve the efficiency of the heat recovery from gas turbine exhaust gas and to maximize the power production in the steam turbine cycle. A simulation code using JavaScript with HTML user interface is used for calculating power and efficiency of the gas turbine cycle, the steam turbine cycle and the combined cycle. By using this code, effect of various operating parameters on the power and efficiency of the combined cycle has been evaluated and it has been concluded that HRSG optimization is much impact on combined cycle power and efficiency.; Two HRSG optimization methods are presented in the present work. One is carried by means of minimization of exergy losses and other is by means of minimization of surface area of HRSG. For the thermodynamic analysis, the selected objective is minimization of thermal exergy losses taking into account only the irreversibility due to the temperature difference between the hot and the cold streams; the exergy analysis is based on the gas-side effectiveness of the sections of the HRSG. From this analysis gas outlet temperature and steam outlet temperature of HRSG calculated, and HRSG effectiveness is improved. For the fixed entropy generation unit's heat transfer area can be minimized. For a counter flow heat exchangers, number of entropy generation units for the heat transfer surface Ns is a strong function of the flow channel aspect ratio L/rh and dimensionless mass velocity g1. Minimum surface area is calculated at various values of capacity ratios and is found the effect of Reynolds number on minimum area.