Modeling and Simulation of Two-Phase Flow Evaporators for Parabolic-Trough Solar Thermal Power Plants

Colección Documentos Ciemat MODELING AND SIMULATION OF TWO-PHASE FLOW EVAPORATORS FOR PARABOLIC-TROUGH SOLAR THERMAL POWER PLANTS JAVIER BONILLA CRUZ LUIS JOSÉ YEBRA MUÑOZ SEBASTIÁN DORMIDO BENCOMO EDUARDO ZARZA MOYA GOBIERNO MINISTERIO DE ESPAÑA DE ECONOMÍA Centro de Investigaciones Y COMPETITIVIDAD Energéticas, Medioambientales y Tecnológicas MODELING AND SIMULATION OF TWO-PHASE FLOW EVAPORATORS FOR PARABOLIC-TROUGH SOLAR THERMAL POWER PLANTS JAVIER BONILLA CRUZ LUIS JOSÉ YEBRA MUÑOZ SEBASTIÁN DORMIDO BENCOMO EDUARDO ZARZA MOYA Es propiedad: EDITORIAL CIEMAT Avda. Complutense, 40 28040-MADRID 2013 Catálogo general de publicaciones oficiales http://www.060.es Depósito Legal: M-28846-2013 ISBN: 978-84-7834-705-6 NIPO: 721-13-044-9 El CIEMAT no comparte necesariamente las opiniones y juicios expuestos en este documento, cuya responsabilidad corresponde únicamente a los autores. Modeling and Simulation of Two-phase Flow Evaporators for Parabolic-Trough Solar Thermal Power Plants Javier Bonilla Cruz Luis José Yebra Muñoz Sebastián Dormido Bencomo Eduardo Zarza Moya Plataforma Solar de Almería Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas 2013 To my girlfriend, Rocío, my parents, Cecilio and Mª Angeles, and my brother, Carlos. Javier Bonilla Cruz Research is the process of going up alleys to see if they are blind. Marston Bates Acknowledgments The authors of this book would like to express their gratitude in the following paragraphs to all the people that have contributed, to a greater or lesser extent, to the development of this book, because it would not have been possible without their invaluable support. Please forgive us if we forget to mention someone in the following lines. We gratefully acknowledge the funding received towards this book and work in the Automatic Control Group at Plataforma Solar de Almería (PSA) from Centro de Investigaciones Energéticas MedioAmbientales y Tecnológi- cas (CIEMAT). We are indebted to the reviewers of this book, Dr. Lidia Roca, Dr. Jose Domingo Álvarez, Alberto de la Calle and Dr. Maria Isabel Roldán, for their corrections, advice and recommendations which contributed to improving this manuscript. We consider it an honor and a privilege to work with Prof. François E. Cellier, for his reviews, advice and sharing work. This first author is also very grateful for the invitation to work at Eidgenössische Technische Hochschule (ETH) Zurich and the chance to attend to mathematical modeling of physical systems lectures. At CIEMAT - PSA, we are very grateful to all the personnel, but specially to our colleagues at the Automatic Control Group – Dr. Lidia Roca, Alberto de la calle, Juan Luis Rivas and David Argüelles – for the discussions, advice and shared work in different projects. My gratitude is also extended to Dr. Loreto Valenzuela, for her help in obtaining experimental data to validate the models. At Centro de Investigación de Energía SOLar (CIESOL), we would like to express our deeper appreciation to Dr. Manuel Pérez, Dr. Jose Domingo Álvarez, Dr. Manuel Pasamontes, Dr. Maria del Mar Castilla, Luis Castillo and Ricardo Silva for our discussions, jokes and shared coffees and lunches. At Universidad de ALmería (UAL), we would like to thank the mem- bers of the Automatic Control, Electronics and Robotics Group (TEP-197), especially Dr. Manuel Berenguel, Dr. Francisco Rodríguez Dr. Jose Luis Guzmán, Dr. Ramón Gonzalez, Dr. Andrzej Pawlowski and Jorge Anto- nio Sánchez. We shared discussions, advice and work with them. We wish to thank Dr. Luis Iribarne for his help, recommendations and suggestions regarding reading materials about cubic splines. We wish to thank José Ignacio Zapata and Dr. John Pye from the Aus- tralian National University (ANU), for their interest in our work, sharing results and knowledge about switching moving boundary models. We really appreciate the know-how, recommendations and advice provid- ed by Dr. Francesco Casella from the Politecnico di Milano about chattering in discretized homogeneous two-phase flow models and the object-oriented design of switching moving boundary models. vii viii Acknowledgments The first author would like to say thank you very much to his family and friends. Special mention goes to his parents, Cecilio and Mª Angeles, his brother Carlos and his girlfriend Rocío who always encouraged and supported him in this endeavor. Abstract The main goal of this work was to contribute in modeling horizontal two- phase flow boiling channels (evaporators) for parabolic-trough solar thermal power plants. The evaporator model is essential for the design of control schemes. Computational fluid dynamics were applied in order to model and discretize the evaporator. Finite volume and moving boundary models were explored in this work. However, some issues in the dynamic simulation of finite volume models, i.e. chattering, did not allow for taking full advantage of dynamic simulations. Furthermore, none of the current moving boundary models considered dynamic switching between all possible flow configurations in evaporators for parabolic-trough solar thermal power plants. The developed evaporator models were obtained from physical principles. The object-oriented equation-based modeling paradigm, which was considered for the design of the dynamic evaporator models, contributed to model maintenance, reusability and decoupling. The equation-based modeling paradigm increased reusability further, by not fixing the causality and thus making the models suitable for a wider range of experiments and simulations. In order to validate the evaporator models, experimental data from a direct steam generation parabolic-trough solar thermal power plant was used –theDIrect Solar Steam (DISS) facility owned by Centro de Investigaciones Energéticas MedioAmbientales y Tecnológicas (CIEMAT)-Plataforma Solar de Almería (PSA), a Spanish government research and testing center. This work makes contributions to the field of modeling and simulation of dynamical systems. A chattering study of finite volume homogeneous two- phase flow dynamic models is presented. The general solutions employed to solve the chattering problem were analyzed, and particular approaches were implemented: Mean Densities and the Heuristic approaches, enabling discretized models to be simulated effectively. New mathematical moving boundary models were developed in order to support dynamic switching between all possible flow configurations for evaporators and condensers, and an equation-based object-oriented library was also implemented to test the integrity and stability of the moving boundary models. Approaches to solve chattering in finite volume models and new moving boundary models were validated against experimental data taken from the DISS facility. For this purpose, different DISS models were implemented, by considering finite volume and moving boundary models. Some unknown pa- rameters were calibrated using a multi-objective genetic algorithm. Finally, these DISS models were compared against experimental data from the DISS facility in terms of accuracy and performance. In order to facilitate these tasks, simulation and calibration frameworks were defined. ix x Abstract All the developed DISS models, composed of finite volume and moving boundary evaporator models, were exposed to a wide range of operating conditions and disturbances, proving that they can take full advantage of dynamic simulations and can be used for the design, testing and validation of advanced control systems. Contents Acknowledgments vii Abstract ix Contents xi List of Figures xix List of Tables xxiii List of Acronyms xxv List of Abbreviations xxix Nomenclature xxxi I Introduction 1 1 Introduction and Document Structure 3 1.1 Context and Scope ........................ 3 1.2 Goals ............................... 6 1.3 Document Structure ....................... 7 1.4 Scientific Contributions ..................... 10 1.4.1 Scientific Contributions Included in this Book ..... 10 1.4.2 Scientific Contributions Related to this Work ..... 11 1.5 Research Projects ......................... 12 II Theoretical Background 13 2 Modeling & Simulation 15 2.1 System ............................... 15 2.2 Experiment ............................ 16 2.3 Model ............................... 16 2.4 Simulation ............................. 16 2.5 Motivation ............................. 17 2.6 Classification of Mathematical Models ............. 17 2.6.1 Black-Box, White-Box and Grey-Box Models ..... 18 2.6.2 Linear and Nonlinear Models .............. 18 2.6.3 Dynamic and Static Models ............... 18 xi xii Contents 2.6.4 Continuous, Discrete and Hybrid Models ........ 18 2.6.5 Variable-structure and Static-structure Models .... 19 2.6.6 Deterministic and Probabilistic Models ......... 19 2.6.7 Quantitative and Qualitative Models .......... 19 2.7 Modeling ............................. 19 2.7.1 Modeling Paradigms ................... 20 2.8 Classification of Simulations ................... 21 2.8.1 Static and Dynamic Simulations ............ 21 2.8.2 Continuous, Discrete and Hybrid Simulations ..... 22 2.9 Simulation Techniques ...................... 22 2.9.1 Transforming Mathematical Models to be Solvable .. 23 2.9.2 Solving Mathematical Models .............. 23 2.10 Evolution of Mathematical Modeling & Simulation ...... 25 2.11 The Modelica Language ..................... 28 2.11.1 Main Features ....................... 28 2.11.2 Modelica Standard Library ............... 30 2.11.3 Modelica Tools ...................... 30 2.12 Summary and Conclusions

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