ENERGY AND EXERGY ANALYSIS OF A PASSIVE AND ACTIVE SOLAR DISTILLATION SYSTEMS
by
VIMAL DIMRI
Centre for Energy Studies
Submitted in fulfilment of the requirements of the degree of
Doctor of Philosophy
to the
Indian Institute of Technology Delhi
July, 2007
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Certificate
It is certified that the thesis entitled, "Energy and Exergy Analysis of A Passive and Active Solar Distillation Systems", submitted by Vimal Dimri to Indian Institute of Technology, Delhi is worthy of consideration for the award of the degree of 'Doctor of Philosophy' and is a record of the original bonafide research work carried out by him under our guidance and supervision. The results contained in the thesis have not been submitted in part or full to any other University or Institute for the award of any degree or diploma.
A
Dr. A. Chandra Professor
Centre for Energy Studies Indian Institute of Technology Hauz Khas, New Delhi- 110016
Dr. GN.Tiwari Professor
Centre for Energy Studies Indian Institute of Technology Hauz Khas, New Delhi- 110016
Date: July 24, 2007
Acknowledgements
I feel immense pleasure to express my heart felt gratitude to my supervisor, Prof G.N. Tiwari for his constant and consistent inspiring guidance and utmost co-operation at every stage which culminated in successful completion of my research work. I also would like to thank my co-supervisor Prof A. Chandra for his inspiration and guidance for my research work.
I am very much thankful to Prof. M.S. Sodha (FNA), Prof. M.K.G. Babu, Head, Prof S. N. Garg and Dr. Subodh Kumar of Centre for Energy Studies for their kind advice and help from time to time. I am also thankful to Prof. V. K. Srivastava for valuable timely suggestions for my research work.
I express my utmost obligation to Mr. Arvind Chel for providing me all possible helps extended to me to complete this daunting task of research work and also providing me the support by taking keen interest in my work and helping me from time to time. My special thanks to Mrs. Geetanjali Chel, wife of Mr. Arvind Chel for her kind support and encouragement.
My sincere thanks go to my colleagues and to my friends Dr. Rajesh Tripathi, Dr. Bikash Sarkar, Dr. M. K. Ghosal, Dr. H. N. Singh, Dr. Anil Kumar, Dr. Anand Joshi, Ms. Tribeni Das and Mr. Jamil Ahmed.
I owe my profound gratitude to my wife Smt. Uma Dimri, daughter Neha Dimri, son Gaurav Dimri and my parents who have been a constant source of inspiration without which I would not have completed this work. I have no befitting words to express my deep sentiments to them for their wholehearted support and patience during the period of study.
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I along with my family members extend our deep sense of obligation to Mrs. Kamlawati Tiwari and her children for their high degree of hospitality, blessings and encouragement throughout my study.
Last but not the least, I convey my sincere thanks to Mr. Lakhrni Chand, Mr. Dhanne Singh, Mr. Umesh Kumar Mishra, Mr. Satish Kumar Jaiswal and all staff members of CES, IIT Delhi for their kind support and help in completing this research work.
Date: July 24, 2007 VIMAL DIMRI
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Abstract
At present, one of the foremost challenges in front of the entire world is to obtain fresh water from the natural resources of water so as to meet the growing demand of fresh water for domestic as well as industrial use. The water resources like rivers, lakes and underground reservoirs contain a large number of micro-organisms which affect health of human beings. However, the water after distillation can be used for domestic as well as industrial use. The conventional methods for distillation are energy intensive techniques and require fast depleting sources of energy. In such circumstances, solar energy is the oldest form of energy available to mankind and is abundant in nature, provides the best alternative to obtain fresh water by with the help of solar still.
The rate of distillate output from solar still mainly depends on operating temperature, shape and material of condensing cover. Further, it is important to study the behavior of heat and mass transfer relation as a function of operating temperature and material of condensing cover. It is to be noted that the primary aim of most of the research work done in the field of solar distillation is to increase the yield of the distiller unit, which can be attained by maximizing the temperature difference between water and
the condensing cover. Hence the design parameters should be employed efficiently to attain the above-mentioned aim. Solar intensity and ambient air temperature are interrelated to each other. Higher solar intensity leads to high temperature inside the solar still and hence results in higher temperature of water in it. It is essential that the solar radiation falling on solar still should contribute towards the enhancement of temperature of water, especially during winter months. Also, the higher operating temperature of solar still water can be achieved using solar collectors input to the conventional solar still.
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Ambient air temperature is the most critical climatic factor during winter. In the winter season the day length is short and also the altitude angle of the Sun is very low.
In the present work, the thermal and computer models for passive and active solar stills have been developed based on the assumptions that inner and outer condensing cover temperatures are different. The active solar still has been integrated with different types of solar collectors like flat plate collector, evacuated tube collector (ETC), ETC with heat pipe and concentrating collector and their daily yield values are compared.
Exergy analysis of both passive and active solar stills has also been carried out.
Parametric study of passive and active solar stills has also been carried out. The performance of solar still has been evaluated based on the inner condensing cover temperature. The effect of inner and outer condensing cover temperatures have been studied and the percentage error involved in the daily yield of solar still is estimated.
Contents
Page Certificate
Acknowledgements ii
Abstract iv
Contents vi
List of Figures
List of Tables xiv
Nomenclature xv
Chapter -I General Introduction 1-19
1.1 Introduction 1
1.2 Historical review 3
1.3 Principle of solar distillation: A state of art 4
1.4 Basic heat and mass transfer 5
1.4.1 External heat transfer coefficient 5
1.4.2 Internal heat transfer 6
1.5 Classification of solar distillation systems 7
1.6 Performance of solar still 10
1.7 Global status of solar distillation 11 Chapter -II Experimental Validation of Thermal Model 20-44
2.1 Introduction 20
2.2 Materials and methods 22
2.2.1 Experimental setup 22
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2.2.2 Instrumentation and observations 23
2.3 Thermal modeling 18
2.3.1 Inner and outer glass cover 24
2.3.2 Basin liner 26
2.3.3 Water mass 27
2.3.4 Flat plate collector 27
2.3.5 Water temperature 29
2.3.6 Hourly yield 29
2.3.7 Daily yield 29
2.4 Overall thermal efficiency 30
2.4.1 Passive solar still 30
2.4.2 Active solar still 30
2.5 Statistical analysis 30
2.5.1 Coefficient of correlation (r) 30 2.5.2 Root mean square percent deviation (e) 30
2.6 Results and discussion 31
2.7 Conclusions 44
Chapter -III Parametric Study of Passive and Active Solar Still 45-59
3.1 Introduction 45
3.2 Passive and active solar stills 46
3.3 Parametric study of passive and active solar stills 47
3.3.1 Hourly yield 47
3.3.2 Daily yield 47
3.3.3 Overall thermal efficiency of passive solar still 48 3.3.4 Overall thermal efficiency of active solar still 48
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3.4 Results and discussion 49
3.5 Conclusions 57
Chapter —IV Comparative Thermal Performance Analysis of 60-71 an Active Solar Still
4.1 Introduction 60
4.2 Active solar still integrated with different types of solar collectors 61
4.2.1 Flat plate collector 61
4.2.2 Concentrating collector 61
4.2.3 Evacuated tube collector 63
4.2.4 Evacuated tube collector with heat pipe 64
4.3 Results and discussion 65
4.4 Conclusions 71
Chapter -V Exergetic Analysis of Passive and Active Solar Still 72-87
5.1 Introduction 72
5.2 Exergy input to passive and active solar stills 74
5.3 Exergy analysis of solar stills 75
5.4 Overall instantaneous thermal efficiency of solar stills 77
5.4.1 Passive solar still 77
5.4.2 Active solar still 77
5.5 Exergy efficiency of solar stills 77
5.5.1 Exergy input to passive solar still 78 5.5.2 Exergy input to active solar still 78
5.6 Results and discussion 79
5.7 Conclusions 87
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Chapter -VI Conclusions and Recommendations 88-89
7.1 Conclusions 88
7.2 Recommendations 89
References 90
Brief Bio-Data of the Author 101
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