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Sustainable Energy Conversion Through the Use of Organic Rankine Cycles for Waste Heat Recovery and Solar Applications

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Sustainable Energy Conversion Through the Use of Organic Rankine Cycles for Waste Heat Recovery and Solar Applications ENERGY SYSTEMS RESEARCH UNIT AEROSPACE AND MECHANICAL ENGINEERING DEPARTMENT UNIVERSITY OF LIÈGE Sustainable Energy Conversion Through the Use of Organic Rankine Cycles for Waste Heat Recovery and Solar Applications. in Partial Fulfillment of the Requirements for the Degree of Doctor of Applied Sciences Presented to the Faculty of Applied Science of the University of Liège (Belgium) by Sylvain Quoilin Liège, October 2011 Introductory remarks Version 1.1, published in October 2011 © 2011 Sylvain Quoilin 〈►[email protected]〉 Licence. This work is licensed under the Creative Commons Attribution - No Derivative Works 2.5 License. To view a copy of this license, visit ►http://creativecommons.org/licenses/by-nd/2.5/ or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA. Contact the author to request other uses if necessary. Trademarks and service marks. All trademarks, service marks, logos and company names mentioned in this work are property of their respective owner. They are protected under trademark law and unfair competition law. The importance of the glossary. It is strongly recommended to read the glossary in full before starting with the first chapter. Hints for screen use. This work is optimized for both screen and paper use. It is recommended to use the digital version where applicable. It is a file in Portable Document Format (PDF) with hyperlinks for convenient navigation. All hyperlinks are marked with link flags (►). Hyperlinks in diagrams might be marked with colored borders instead. Navigation aid for bibliographic references. Bibliographic references to works which are publicly available as PDF files mention the logical page number and an offset (if non-zero) to calculate the physical page number. For example, to look up [Example :a01, p. 100-80] jump to physical page 20 in your PDF viewer. Abstract This thesis contributes to the knowledge and the characterization of small- scale Organic Rankine Cycles (ORC). It is based on experimental data, thermodynamic models and case studies. The experimental studies include: 1. A prototype of small-scale waste heat recovery ORC using an open-drive oil-free scroll expander, declined in two successive versions with major improvements. 2. A prototype of hermetic scroll expander tested on vapor test rig designed for that purpose. The achieved performance are promising, with expander overall isentropic effectivenesses higher than 70% and cycle efficiencies comparable or higher than the typical efficiencies reported in the scientific literature for the considered temperature range. New steady-state semi-empirical models of each component are developed and validated with the experimental data. The global model of the ORC prototype allows predicting its performance with a good accuracy and can be exploited to simulate possible improvements or alternative cycle configurations. Dynamic models of the cycle are also developed for the purpose of evaluating the system's reaction to transient conditions. These models are used to define and compare different control strategies. The issues of cycle optimization and fluid selection are treated using the steady-state semi-empirical models. The thermodynamic optimization of such cycles is first demonstrated by practical examples. Furthermore, three different methods for fluid selection are proposed, investigated and compared. Their respective advantages and fields of application are described. Finally, two prospective studies of small-scale ORC systems are proposed. The first one is a solar ORC designed for the rural electrification of remote regions in Africa. This prototype aims at competing with the photovoltaic technology, with the advantage of generating hot water as by-product. The second prospective study deals with the recovery of highly transient heat sources. Advanced regulation strategies are proposed to address the practical issues of such systems. These strategies are compared with the state-of-the- art strategies and show a non-negligible potential of performance improvement. v Acknowledgments I would like to thank Professor Vincent Lemort for his trust and his support during the whole period of this work. I wish to thank him for the numerous moments spent working together on practical and theoretical issues as well as for countless valuable discussions. I am also grateful to professor Jean Lebrun, who gave me the opportunity to start this thesis and provided constructive advices along the work. Thank you to the members of the Thesis Committee, Piero Colonna, Assaad Zoughaib, Georges Heyen, Philippe Ngendakumana and Pierre Duysinx for their valuable comments and constructive criticism. A large part of this work would not have been possible without the trust of colleagues from foreign laboratories, namely Matthew Orosz, Andreas Schuster, Richard Aumann and their respective teams. They allowed me to gain valuable experience and know-how and warmly welcomed me to stay in their labs. Special thanks goes to Stéphane Bertagnolio and all the members of the Thermodynamics Laboratory for their help and availability, but above all for their friendship and the great moments spent together during these four years. Furthermore, I want to thank my family and my friends for their support and encouragements throughout my studies. Last but not least, special thanks to Jessica Schrouff for her unwavering support, for the proofreading and for the multiple comments and advices to improve this thesis. vii Table of contents ► Abstract..........................................................................................v ► Acknowledgments.......................................................................vii ► Table of contents.........................................................................ix ► Nomenclature..............................................................................xiii ► Chapter 1: Introduction...................................................................................1 ► Chapter 2: The Organic Rankine Cycle .........................................................1 ►1 Introduction......................................................................................1 ►2 Applications......................................................................................2 ►2.1 Biomass combined heat and power...............................................2 ►2.2 Geothermal energy........................................................................4 ►2.3 Solar power plants.........................................................................5 ►2.4 Heat recovery on mechanical equipment and industry processes 7 ►2.5 Heat recovery on internal combustion engines..............................7 ►3 Comparison with the steam Rankine Cycle......................................9 ►4 Expansion machines.......................................................................12 ►4.1 Turbomachines............................................................................12 ►4.2 Positive displacement expanders.................................................13 ► Chapter 3: Experimental setups.....................................................................1 ►1 Introduction......................................................................................1 ►2 ORC test bench.................................................................................3 ►2.1 Description.....................................................................................3 ►2.2 Measurements ..............................................................................7 ►2.3 Achieved performance...................................................................9 ►3 Improved ORC test bench...............................................................12 ►3.1 Description...................................................................................12 ►3.2 Test results..................................................................................15 ix Table of contents ►4 Expander test rig............................................................................18 ►4.1 Description of the test rig............................................................18 ►4.2 Measurement devices..................................................................21 ►4.3 Overall measured performance...................................................21 ►4.4 Impact of oil mass fraction on performance.................................24 ►5 Conclusions....................................................................................25 ► Chapter 4: Modeling.........................................................................................1 ►1 Introduction......................................................................................1 ►2 Steady-state modeling.....................................................................2 ►2.1 Models............................................................................................2 ►2.2 Heat exchangers..........................................................................12 ►2.3 Pump............................................................................................18 ►2.4 Cycle model.................................................................................19 ►2.5 Model exploitation........................................................................21 ►3 Dynamic models.............................................................................27 ►3.1 Heat exchangers model...............................................................27
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