Optimization of heat recovery steam generators for combined cycle gas turbine power plants Manuel Vald es a, * , Jos  e L. Rap un b a Departamento de Ingenier  õa Energ etica y Fluidomec  anica, Universidad Polit ecnica de Madrid, E.T.S. Ingenieros Industriales, Jos e Guti errez Abascal 2, 28006 Madrid, Spain b IBERDROLA Ingenier  õa y Consultor  õa, Avda de Burgos 8B, 28036 Madrid, Spain Received 3 June 2000; accepted 12 November 2000 Abstract The heat recovery steam generator HRSG) is one of the few components of combined cycle gas turbine power plants tailored for each speci®c application. Any change in its design would directly aect all the variables of the cycle and therefore the availability of tools for its optimization is of the greatest relevance. This paper presents a method for the optimization of the HRSG based on the application of in¯uence coecients. The in¯uence coecients are a useful mathematical tool in design optimization problems. They are obtained after solving the equations of the system through the Newton±Raphson method. The main advantage of the proposed method is that it permits a better understanding of the in¯uence of the design parameters on the cycle performance. The study of the optimization of the distribution of the boiler area between its dierent components is presented as an example of the proposed technique. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Heat recovery steam generator; Boiler design optimization; In¯uence coecients 1. Introduction The design of the combined cycle gas turbine CCGT) power plant is inherently complex due to the existence of two dierent power cycles which are coupled through the heat recovery steam generator HRSG). The HRSG is the nexus between the gas cycle and the steam cycle, therefore any change in its design directly aects the cycle eciency, its power generation, the global cost, and many other variables in the cycle. Applied Thermal Engineering 21 2001) 1149±1159 www.elsevier.com/locate/apthermeng * Corresponding author. Fax: +34-1-3363006. E-mail addresses: mvaldes@etsii.upm.es M. Valde Âs), jrj@iberdrolaingenieria.es J.L. Rapu Ân). 1359-4311/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S1359-431100)00110-1