Thermodynamic modeling based optimization for thermal systems in heat recovery steam generator during cold start-up operation Peyman Sindareh-Esfahani a , Ali Ghaffari a , Pouria Ahmadi b, * a Department of Mechanical Engineering, K.N. Toosi University of Technology, Pardis St., Vanak Sq., Tehran, Iran b Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe St. North, Oshawa, ON L1H 7K4, Canada highlights  A comprehensive model for thermal systems in HRSGs, cold start-up is presented.  Two parameter identification algorithms are applied to the model.  A designed parameter identification algorithm based on GA is presented.  The aspects of the model and proposed parameter identification algorithm are studied.  Application of experimental data in order to modeling and validation experiments. article info Article history: Received 1 August 2013 Accepted 14 November 2013 Available online xxx Keywords: Modeling Adaptive parameter identification Genetic algorithm Heat recovery steam generator Cold start-up abstract In this research paper, a comprehensive thermodynamic model of a thermal system in a dual pressure heat recovery steam generator during cold start-up operation is presented. The model consists of un- known parameters identified by two parameter identification techniques. The first algorithm is an online adaptive parameter identification algorithm which is based on gradient algorithm with integral cost function and forgetting factor. Second algorithm is a designed parameter identification algorithm based on the genetic algorithm method. Results are compared with a broad set of actual data taken from one of the Iranian power plants during cold start-up. Simulation results represent the effectiveness and reli- ability of the developed model and each of two parameter identification techniques. A comprehensive study is carried out in order to compare two applied techniques. The first technique leads to time-varying parameters and the second reaches the constant parameters with a piecewise model. In order to achieve a simulated model for heat recovery steam generator cold start-up, the costs of the modeling and identification process, and the concepts of the optimization lead to the designed algorithm based on genetic algorithm. Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. 1. Introduction Over the past few decades, the number of combined cycle power plants has increased due to their higher thermal efficiency than individual steam or gas turbine cycles. A heat recovery steam generator is a kind of heat exchanger used in CCPPs and is a connector between gas turbine and steam turbine cycle. An HRSG produces steam by using the exhaust gases from gas turbine. The produced steam feeds to the steam turbine to generate electricity. The combination of gas turbine, steam turbine, and HRSG makes the possibility of reaching more efficiency and less emissions [1]. One of the most critical operations of HRSG is the start-up stage; because in this stage, there are some concurrent fulfillments of conflicting objectives such as maximizing the pro- duced energy and minimizing the pollutant emissions [2e4]. Some studies concentrate on the problem of CCPP start-up optimization to reduce the start-up time and pollutant emissions [5e8]. Furthermore, increasing the produced energy considering the limitation of temperature and pressure gradients is also taken into account in these studies. In order to control the key parameters of HRSG such as temperature and pressure during cold start-up and optimize this stage based on the defined objective functions and constraints, it is necessary to have a comprehensive model of the HRSG cold start-up [9]. Previous studies focused on dynamic modeling in steady state and transient conditions can be divided into three categories. The * Corresponding author. Tel.: þ1 289 6009505. E-mail addresses: Peyman.Sindareh@gmail.com (P. Sindareh-Esfahani), Ghaffari@kntu.ac.ir (A. Ghaffari), Pouria.Ahmadi@uoit.ca, pouryaahmadi81@gmail. com (P. Ahmadi). Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng 1359-4311/$ e see front matter Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.applthermaleng.2013.11.031 Applied Thermal Engineering xxx (2013) 1e11 Please cite this article in press as: P. Sindareh-Esfahani, et al., Thermodynamic modeling based optimization for thermal systems in heat recovery steam generator during cold start-up operation, Applied Thermal Engineering (2013), http://dx.doi.org/10.1016/ j.applthermaleng.2013.11.031