Technische Universität München Institut für Energietechnik Lehrstuhl für Thermodynamik Experimental and Numerical Analysis of a PCM-Supported Humidification-Dehumidification Solar Desalination System Abdel Hakim M. A. Hassabou Vollständiger Abdruck der von der Fakultät für Maschinenwesen der Technischen Universität München zur Erlangung des akademischen Grades eines DOKTOR – INGENIEURS genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr.-Ing. Dirk Weuster-Botz Prüfer der Dissertation: 1. Univ.-Prof. Wolfgang H. Polifke, Ph. D. (CCNY) 2. Prof. Abdalla Hanafi, Ph. D., University of Kairo / Ägypten Die Dissertation wurde am 27.09.2011 bei der Technischen Universität München eingereicht und durch die Fakultät für Maschinenwesen am 10.11.2011 angenommen. Preface First and foremost I thank the Greatest Creator for his countless blessings and neat creation: “He sends down rain from the sky and with it gives life to the earth after it is dead: Verily in that are signs for those who are wise.” [Al- Qur’aan 30:24]. “It is He Who has let free the two bodies of flowing water: one palatable and sweet, and the other salty and bitter; yet has He made a barrier between them, and a partition that is forbidden to be passed.” [Al-Qur’aan 25:53]. “It is He Who created The Night and the Day, and the sun and the moon: All (the celestial bodies) Swim along, each in its rounded course.” [Al-Qur’aan 21:33]. “It is not permitted to the Sun to catch up the Moon, nor can the Night outstrip the Day: Each (just) swims along in (its own) orbit (According to Law).” [Al-Qur’aan 36:40]. I would like to express my deep appreciation and gratitude to my advisors: Prof. Wolfgang Polifke, Dr-Eng. Markus Spinnler, Lehrstul für Thermodynamik, Technische Universität München (TUM), Germany, and Prof. Abdalla Hanafi, Faculty of Engineering Cairo University, for their continuous guidance, support, advices, and valuable time. I thank Allah for blessing me with such great advisors. I’m deeply grateful to Prof. Polifke for his brilliant insights and many inspiring ideas which helped me to develop better understanding and careful numerical and theoretical analysis. I have learned a great deal from him how to buildup argumentations and maintain a clear sense of purpose. My appreciation for him as a scientist and as a person outpaces the limits of acknowledgement words. I would like to thank prof. Hanafi for his support and encouragement to apply for the Ph.D. scholarship and conduct my research abroad. I appreciate the time, guidance, and efforts Prof. Hanafi provided to my research from preliminary stages to the conclusion. I also thank Prof. Hanafi for teaching me the Computational and Numerical Methods in Heat Transfer and Fluid Mechanics in my post graduate studies. A very special word of thanks goes to Dr. Markus Spinnler; Head of the Solar Research Center at TUM for making my research as smooth as possible. His early and continued technical and administrative supports were invaluable. He formulated the research proposal of my Ph.D. study and was leading the technical and administrative correspondences of my scholarship for securing the financial means and laboratory facilities. He also was very helpful in advising and discussing lab problems and experimental analysis as well proof reading of the dissertation and providing many valuable comments in concluding the study. His sense of humour and friendliness hospitality for me and my family in Germany were enjoyable and will never be forgotten. i It is my pleasure to thank Prof. Thomas Sattelmayer, Head of the Lehrstul für Thermodynamik, TUM and all the administrative and supporting staff, who were abundantly helpful and offered invaluable assistance, and great hospitality. I would like to express my deep thanking to my colleague, Dipl.-Eng. Burkhard Seifert for his support and valuable discussions during the course of the study. This research project is co-funded by the Middle East Desalination Research Center (MEDRC) through the Ph.D. scholarship grant number 05-AS-003, and TUM, Germany. The financial support of MEDRC and TUM is gratefully acknowledged and appreciated. I’m fully indebted to my great parents for their unconditional loving and support throughout my whole life. I cherish the support in all life situations and friendship of my brothers and sister; Gamal, Usama, and Walaa. I am heartily thankful to Dr-Eng. Jürgen Blumenberg and his wife; Mrs. Gaby. Their great friendship and close social relationships made my family stay in Germany very pleasant. Thanks for never letting us feel that there was a long distance between us and our dear friends and families in our home country; Egypt. Last but not least, I owe my deepest gratitude to my lovely wife Abear for her patience, providing a supportive environment for me, and taking over major responsibilities of our kids. The long trip would have been very harsh and I could not have achieved as much as I did without her enduring support. Finally I can not describe how appreciative I’m to my three kids; my daughter Salma, my son Noureldin, and my little daughter Manar. The innocent smiley faces were always motivating and triggering my advancement. Whatever I achieve will be dedicated to make your future bright. München, September 2011 Abdel Hakim Hassabou ii Abstract This work discusses the results of experimental and theoretical studies on a humidification-dehumidification (HDH) water desalination system equipped with phase change material (PCM) as a packing media in all its main components. The PCM-supported HDH system consists of an evaporator and condenser comprised by two cylindrical direct-contact packed beds filled with spherical PCM packing elements. Moreover, a solar collector and an external PCM thermal storage are used to drive the HDH plant. The external PCM thermal storage is used to guarantee continuous operation of the plant day and night round the clock under the transient behaviour of solar irradiation. The objective of using PCM elements in the evaporator and condenser was for heat storage as a back up during cloudy hours or for part-time night operation. During analysis of steady state conditions, it was discovered that the PCM packing media seem to enhance their thermal performance through locally establishing multiple- effects of heating/humidification (MEHH) and cooling/dehumidification (MECD) while air passing through the successive packing layers in the evaporator and condenser respectively. The multiple-effect phenomena are attributed solely to existence of conductive packing media, which act as heat and mass exchangers. Thus, the focus of the study lies on the thermal conductivity rather than the thermal capacity or solid- liquid phase change processes of the packing in the two columns. The major aim of this study is to examine systematically the effect of MEHH and MECD at enhanced thermal conductivity of the filling material and to determine the technical and economic feasibility of applying these concepts in HDH desalination plants under steady state operation conditions. Transient simulation models for the individual components in the HDH system have been established and validated against experimental measurements. Using both experiment and simulation, a detailed heat and mass transfer analysis for the performance of the evaporator and condenser over a wide range of operation conditions under steady state has been performed using different types of packing materials. Furthermore, a yearly parametric analysis for the whole HDH plant has been performed under real weather conditions for two locations in Egypt. The overall performance analysis focuses on the optimum operation conditions of the HDH system, with optimum conductive filling material, with and without external PCM thermal buffer. Special attention is paid to the effect of climatic conditions and comparison between PCM and water as storage media in the external thermal storage. iii Contents List of figures ............................................................................................................ viii List of Tables ............................................................................................................. xi List of Frames ............................................................................................................ xi 1 Introduction ............................................................................................................. 1 1.1 Fresh water challenges ..................................................................................... 1 1.2 Desalination option ........................................................................................... 2 1.3 Overview on desalination processes................................................................. 2 1.3.1 Energy requirements and water cost ...................................................... 4 1.3.2 Selection criteria of desalination technology ........................................... 5 1.3.3 Coupling desalination plants with power plants....................................... 6 1.3.4 Coupling renewable energies with desalination technologies ................. 6 1.3.5 Barriers and limitations of RE-desalination ............................................. 8 1.4 Solar desalination ............................................................................................. 9 1.4.1 Conventional solar stills .......................................................................... 9 1.4.2 Humidification-Dehumidification technique ..........................................