The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore
Foreword by Akhtar Kalam
At the present situation, for the major chunk of global population, satisfying their basic needs like energy, food, clean water and housing cannot be achieved because of the demand for energy is far much higher than the supply. In this age of energy crisis, there is a strong urge to look for renewable energy sources for the fulfillment of our basic energy need. It is not only provide the energy security but save our precious environment from greenhouse gasses. Solar energy has emerged as one of the prominent renewable energy. Solar radiation is another term used for electromagnetic radiation. By the proper utilization of the radiation, various important activities can be done like drying, water purification, electricity generation, space heating, crop cultivation etc. For developing nations like India, solar food processing is the newest and efficient advanced technology introduced for addressing different problems faced by our citizens. The technology which includes food processing and storage using solar energy can indirectly aid in removing poverty. We do not produce less; the fact is that much of our produce goes as waste as we do not have proper food processing and preservation mechanism in our country. By introducing solar drying technology to our farmers, a revolution can be started and absolute poverty and hunger can be wiped from our country. In majority of Asian countries, agriculture mostly dominates economy. More than half the population is employed in agriculture but still the demand outdoes the supply. One of the major reasons for this being lack of efficient preservation and storage techniques. One of the most popular techniques for preserving food in most of the Asian countries is drying of crops by employing solar energy. Application of solar energy in drying for preserving agricultural and marine produce is in practice since ages. This was done using direct solar radiations. Solar dryers have huge applications in agriculture and industrial sector; especially from an energy point of view, dryers are the most useful devices. These can save energy, save plenty of time, occupy minimal surface area, enhance life and quality of products and most importantly are ecofriendly. Drying rice using solar dryers has been well known for many years especially in the countries producing rice, such as v
Foreword by Akhtar Kalam
Thailand and the other Asian countries. Solar dryers can be used effectively for low temperature drying and hence can be used effectively to dry agricultural produce, flowers, herbs etc. Thus, solar dryers overcome various disadvantages of artificial mechanical dryers, reducing the total amount of fuel energy required. This book has 5 sections and covers 23 chapters. These 5 sections are: (i) (ii) (iii) (iv) (v)
Concept of Solar Drying Design and Testing of Solar Drying Systems Modelling of Solar Drying Systems Environomical Impact of Solar Drying Systems Innovation in Solar Drying
This book edited by Dr. Anil Kumar, who was a respected researcher at the Energy Technology Research Centre, Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Thailand, and at present, Assistant Professor, Dept. of Energy (Energy Centre), Maulana Azad National Institute of Technology, Bhopal (India), and Dr. Om Prakash, Assistant Professor, Department of Mechanical Engineering, from Birla Institute of Technology Mesra, Ranchi-India, is extremely well written and the authors of various chapters have substantial analytical and theoretical knowledge in the subject. A comprehensive review of the various designs, details of construction and operational principles of the wide variety of practicallyrealised designs of solar-energy drying systems has been presented. I commend this book to all undergraduates, postgraduates, researchers and academics interested in acquiring knowledge in this important area. The appropriateness of each design type for application by rural farmers and others in developing countries has been discussed. Some very recent developments in solar drying technology have also been highlighted.
Smart Energy Research Unit, College of Engineering and Science (D524 or D332) Victoria University Ballarat Road, Footscray, 3011, VIC, Australia
Foreword by D. P. Kothari
Solar energy is an ancient subject. In India, the Sun is considered to be God. Women worship the Sun. In fact, all forms of energy emanates from the Sun only. In the future, solar energy will form the major chunk of the energy supplied. India is lucky to have Sun for 220 days in most parts out of 365 days. There are several aspects of solar science and engineering which the students, teachers, researchers and industry personnel have to study, such as solar power generation by PV and solar thermal, solar refrigeration, solar cooker, solar cooling and heating, solar drying, and solar architecture. Out of these, solar drying finds a special place. The book Solar Drying Technology: Concept Design Testing Modeling Economics and the Environment edited by my friends Dr. Om Prakash and Dr. Anil Kumar will fulfil the long felt need of a book in this vital area. It will prove to be a good text/reference book. The main strength of this book is its beauty of combining theory and practice in various chapters written by well-known international experts in the area. Both the editors are well known to me and they have done a fabulous job. As a co-author/co-editor of more than 50 books and as one who has also worked in solar energy and was in the illustrious company of great solar energy experts like Prof. M.S. Sodha, Prof. S.S. Mathur, Prof. H.P. Garg, Prof. G.N. Tiwari, Prof. T.C. Kandpal and other erstwhile colleagues in the Center for Energy studies, IIT Delhi for 30 years, I can safely vouch for the quality of the book. I am sure the readers will immensely benefit by this book.
Indian Institute of Technology, Delhi New Delhi, 110016, Delhi, India
D. P. Kothari
Foreword by Trilochan Mohapatra
Food preservation is very important for food safety and security. Food and Agriculture Organization (FAO) estimated that 852 million people worldwide are undernourished. The global challenge to ensuring food and nutritional security for the fast-growing human population can be addressed through technological development and innovation in agricultural sector. Technology intervention is essential to safeguard against post-harvest losses of agri-produce that continue to happen owing to primitive methods of harvests, handling and storage. Drying of agricultural products is one of the important methods to preserve and enhance shelf-life. Although open sun drying is a very common and cost- effective method, its advantage is partly upset due to quantitative and qualitative losses caused by rodents, birds, insects, dust, rain, over drying and/or under drying. It is extremely important, therefore, to develop energy-efficient drying operations to conserve conventional energy without affecting the quality of the end product. In this regard, solar dryers not only meet the drying requirements of crops, fish and animal products, but also save time, energy and money. I am happy to record that this book is a joint venture of national and international experts whose ideas have been meticulously compiled by the editors highlighting the concept, design, testing, modelling, economics and environmental perspectives of solar dryers for plausible reading and functional adoption. The editors and the authors deserve appreciation for this timely effort.
Indian Council of Agricultural Research Krishi Bhavan New Delhi, 110001, Delhi, India 21 November 2016
The tremendous rise in demand for energy has led to scarcity of conventional sources of energy like fossil fuels, thereby pushing us to search for alternative sources of energy. With the sun being the ultimate source of energy, we need to harness its energy to sustain the growth of mankind. Solar drying has been in practice since ages to preserve different kinds of agricultural produce. Due to advancement in science and technology, we have developed inexpensive and efficient solar drying devices for drying different agricultural and marine products using solar power. Using solar dryer, the amount of moisture can be reduced tremendously, thus preserving the products for a longer time. It reduces product wastage and enhances the productivity of farmers. This book is divided in five parts. The first part deals about the concept of solar drying. In this part, there are five chapters (1, 2, 3, 4, and 5). In Chap. 1, the authors discussed the fundamental concepts of drying such as water activity and its significance, the important properties of air and its products, drying mechanism, drying curves and the performance indicators of a dryer. The fundamental knowledge in drying will enable a better understanding of any solar drying system. In Chap. 2, the author discusses the general classification of solar drying systems. Numerous types of solar dryers have been designed and developed in various parts of the world. A solar dryer can be operated based on either natural or forced convection of heat transfer. Based on the mode of heating source, a solar dryer is classified broadly in three types, namely, direct, indirect and mixed mode solar dryer. The most typical solar dryers for agricultural produce based on their construction designs were described. The selection of solar drying systems should consider the available insolation rate in the target region, kind of product that will be dried, production throughput and operational and investment costs. Most studies consider solar drying as a good alternative to traditional open air drying and/or conventional drying systems operated by fossil fuels.
In Chap. 3, the author deals with the characteristics of the different systems for solar drying of crops. The fundamental concepts and contexts of their use to dry crops are discussed in the chapter. It is shown that solar drying is the outcome of complex interactions between the intensity and duration of solar energy, the prevailing ambient relative humidity and temperature, the characteristics of a particular crop and its pre-preparation and the design and operation of the solar dryer. In Chap. 4, the authors discuss the fundamental mathematical relations of solar drying systems. Basic mathematical relations and theories of the drying process involving simultaneous heat and mass transfer models as well as those of the simplified thin layer and deep bed models are given. An overview of solar drying methods (in both thin layer and deep bed dryers) along with the principal solar drying systems (direct-sun dryers and passive and active dryers) is briefly provided, discussing the respective fields of application and analysing their advantages and disadvantages. Finally, the basic mathematic equations used for describing and modelling the various physical processes within the most common drying systems and devices are reported. A brief discussion of the recent advances in modelling is presented where pertinent. In Chap. 5, the authors discuss the advancement in greenhouse drying system. Greenhouse drying system is one of the most popular solar drying systems. The state-of-the-art advancement in the field of greenhouse drying is also discussed. Part II deals with the design and testing of the solar drying systems. In this part, there are three chapters (6, 7, and 8). In Chap. 6, design procedures for solar drying systems including the use of rules of thumb of psychrometric charts and design equations are discussed. The economic aspects of solar drying systems are also deliberated. Various case studies, relating to the application of direct mode, indirect mode and mixed mode types of solar drying systems, have been presented. Although direct mode dryers are economic to construct, they have major drawbacks such as their drying temperatures cannot be regulated, leading to over- or under-drying. Well-designed solar crop drying systems are capable of drastically reducing losses of agricultural products occasioned by postharvest spoilage. Chapter 7 deals with the thermal testing methods for solar dryers. The standard testing method not only provides better performance management of the dryer system but allows manufacturers to achieve competitive efficiency and good product quality by comparing the available designs. In this chapter, an extensive review of solar dryer performance evaluation has been presented. Furthermore, the chapter describes existing testing procedures for most common designs of solar dryers and related practices used in the measurement, evaluation and description of overall performance, including a variety of food products dried in scientific investigations. Chapter 8 deals with the exergy analysis of solar dryers. Exergy analysis corrects existing inefficiencies at its sources and contributes more meaningful in solar dryer designs. Increased efficiency can often contribute in an environmentally acceptable way by direct reduction of irreversibility that might otherwise have
occurred. Exergy analysis is one of the most powerful mechanisms in order to design an optimum solar dryer. Part III deals with the modelling of the solar dryers. Mathematical and soft computing modelling techniques are discussed. There are six chapters (9, 10, 11, 12, 13, and 14) in this part. In Chap. 9, mathematical modelling of solar drying systems is presented. This chapter begins with a broad appraisal of the basic concepts and essential theories for the mathematical modelling of solar drying. Next, the common modelling approaches and developmental steps (model conceptualization, mathematical formulation, determination of model parameters, method of solution and experimental validation) implicated in solar drying were outlined. Then the sequential progress of thin layer drying models (semi-theoretical, theoretical and empirical models) was discussed briefly. The subsequent section of the chapter reviews the application of the above models by different researchers in the last decade. Afterwards, newly developed or commonly used thin layer drying mathematical equations related to the solar collector models and drying cabinet models for different solar drying systems and food products were shown. Finally, the chapter concludes with future directions and the need for more investigations on solar drying. Chapter 10 deals with the drying kinetics of solar drying systems. This chapter presents the heat and mass transfer mechanisms that regulate the drying rate, the conditions in direct and indirect solar drying, the drying curves and the mathematical modelling of the solar drying processes, with application examples in various dominions. Chapter 11 deals with mathematical and computational modelling simulation of solar drying systems. In mathematical modelling, both fundamental (Fickian diffusion) and semiempirical drying models have been applied to the solar drying of a variety of agricultural commodities in several different dryer types (direct, indirect and mixed mode with both forced and natural convection). Computational modelling (i.e. computational fluid dynamics or CFD), both in 2-dimensional and 3-dimensional modes, affords insights on geometry-specific solar drying issues, such as airflow patterns within the drying cabinet. Both mathematical and computational modelling have recently been brought to bear on solar drying innovations such as thermal storage, use of desiccants during drying and dynamic feedback control of the drying process. Robust models are also necessary for the performance evaluation and comparison of different dryer designs and configurations. The outputs of mathematical and computational models are compared with measured drying data (whether performed outdoors or with a solar simulator) to ensure the accuracy and efficacy of the model. Chapter 12 describes the different numerical methods that can be utilized for the performance evaluation of the solar drying system. Numerical techniques help in developing a solar dryer to increase drying effectiveness and analyses and forecast the performance of dissimilar types of a solar dryer. Numerical analysis is essential for forecasting the relevant parameters, which are highly required in a solar drying system. Computational fluid dynamics (CFD) can be used to analyse and investigate the heat and mass transfer inside the solar dryer. Adaptive-network-based
fuzzy inference system (ANFIS) is able to predict the performance of the solar drying system. The artificial neural network can be applied to estimate the quantity of the dehydrated product. FUZZY logic is an essential tool to precisely forecast the results with least inaccuracy. Numerical techniques are applied for testing the drying behaviour of products in the laboratory as well as commercial level. Chapter 13 deals with simulation of food solar drying. This chapter covers the application of different software in the design and development of solar dryers. This comprehensive and extensive analysis of the different software will be very useful to the research community, academicians and solar dryer designers. Chapter 14 discusses the simulation process of food solar drying, presenting the basic issues of mass and heat transfer under time-varying conditions. Food drying embraces several phenomena, and scientists do not completely understand its underlying mechanisms. However, mathematical simulation and modelling provide comprehension to improve knowledge on drying mechanisms, allow the prediction of the drying behaviour, and are essential tools in the design of solar drying equipment. The major difficulty in simulating solar food drying arises from variable meteorological conditions that change air temperature, moisture and velocity inside the solar equipment, during the drying process. Therefore, an integrated heat and mass transfer model under dynamic conditions is presented, and appropriate assumptions are discussed. A meteorological model and desorption isotherms are taken into consideration as well. The integrated model includes food shrinkage, changing boundary conditions and variable thermal properties and water diffusivity with time and space (non-isotropic characteristics). In Part IV, the environomical impact of solar drying systems is discussed. In this part, there are five chapters (15, 16, 17, 18, and 19). Chapter 15 deals with the economics of solar drying systems. Various methodologies to evaluate the economics of the solar dryer are highlighted. Cost effective drying systems will have great impact on marketing and publicity. Chapter 16 presents the importance of economic consideration of solar dryers and a review of techno-economic study of solar dryers developed over the years with economic and energy analysis. In the present context, this study is important because many types of solar dryers were invented, namely, hybrid solar dryer, direct solar dryer and indirect solar dryer, for various drying applications. However, the availability of a suitable solar drying system which is technically and costeffectively feasible is limited. As of now, only some solar dryers which meet the valued parameters like economical, technical and socio-economical requirements commercially exist. Chapter 17 discusses the holistic approach to the economic analysis of various developed solar dryers. Various important economic analysis parameters are being discussed like annualized cost, capital cost, savings earned in its entire working life and the time required to recover capital investments, payback period with interest and without interest, etc. Chapter 18 presents the economic analysis of hybrid photovoltaic-thermal (PV-T) integrated indirect-type solar dryer. A solar dryer integrating with photovoltaic (PV)-powered DC fan has been developed for forced air circulation without
the use of external power supplies like grid electricity. This dryer has also been coupled to a solar air heater having a sun-tracking facility and blackened surface as absorber for improved energy collection efficiency. A new PV-T integrated solar dryer consists of a solar air heater and a drying chamber with chimney. This system can be used for drying various agricultural products like fruits and vegetables. Experimental studies have been conducted for the forced mode under no load and load conditions. Energy analysis and techno-economic analysis of hybrid PV-T dryer have also been carried out. Chapter 19 presents the energy analysis of the direct and indirect solar drying system. Various important energy analysis parameters such as CO2 discharges per year, embodied energy, energy payback time, carbon mitigation and carbon credit have been considered. This analysis helps to protect the environment from pollution and encourages the use of solar energy. The embodied energy of the greenhouse dryer is calculated. In the last part, various innovations in the solar drying system are discussed. It includes four chapters (20, 21, 22, and 23). Chapter 20 presents energy conservation through recirculation of hot air in a solar dryer. The experiment was conducted in a system where the pneumatic conveyor is applied in the solar drying system. The drying efficiency and the specific energy of the solar dryer with inclined drying chamber were on an average less than the vertical type. The drying capacity (initial load) of the inclined drying chamber was larger than the vertical chamber type. Chapter 21 discusses the development and performance study of solar air heater for solar drying applications. It explores general theoretical thermodynamic performance studies of some improved solar air heater for drying applications, followed with detailed thermal performance studies of an improved hemispherical protruded solar air heater. Economic analysis estimated that if 400 m2 of galvanized roof of black tea processing factory were converted into a solar air heater by using black painting, plywood insulation and tempered glass enclosure, then an average 20 % of conventional thermal energy for black tea drying may be saved. The annual carbon-dioxide reduction of 2189 tonnes is achievable by using improved solar air heater. The payback period of the hybrid renewable thermal energy-based system is less than 15 months, and benefit to cost ratio is 1:1. Chapter 22 includes recent and past research on different thermal storage systems for solar dryers like latent heat storage, sensible heat storage and thermos-chemical storage commonly used for domestic and industrial applications. Chapter 23 provides an idea about the methodology of the promising phase change material (PCM) development through proper mixing and simultaneous measurement of their thermo-physical properties by the differential scanning calorimeter (DSC) thermal analysis technique. Based on the DSC analysis, it may be concluded that the developed binary mixtures were in the melting range of 40–60oC with an adequate amount of latent heat of fusion which can be utilized for the application of solar dryers as well as for other relevant TES applications.
It is hoped that this book is complete in all respects of solar drying technology and can serve as a useful tool to learners, faculty members, practising engineers and students. Despite our best of efforts, we regret if some errors are in the manuscript due to inadvertent mistake. We will greatly appreciate being informed about errors and receiving constructive criticism for the improvement of the book. Ranchi, Jharkhand, India Bhopal, Madhya Pradesh, India
Om Prakash Anil Kumar
This book is tribute to the engineers and scientists who continue to push forwards the practice and technologies of solar drying. These advances continue to reduce postharvest crop/fruit losses and promote sustainable crop/food drying technology. This book could not have been written without the efforts of numerous individuals including the primary writers, contributing authors, technical reviewers and practitioners who contribute real-life experience. Our first and foremost gratitude goes to the God Almighty for giving us the opportunity and strength to do our part of service to the society. We express our heartfelt gratitude to the president of Prince of Songkla University, Hat Yai, Songkhla, Thailand; the director of Maulana Azad National Institute of Technology Bhopal, India; and the vice chancellor of the Birla Institute of Technology, Mesra, Ranchi, India, for their kind encouragement. We would like to thank our teachers Prof. G. N. Tiwari, Centre for Energy Studies, Indian Institute of Technology Delhi, India, and Prof. Perapong Tekasakul, Vice President (Research System and Graduate Studies) of Prince of Songkla University, Hat Yai, Songkhla, Thailand, for building up our academic and research career. We are indebted to Dr. Trilochan Mohapatra, Secretary and Director General of the Department of Agricultural Research and Education, Indian Council of Agricultural Research, Ministry of Agriculture & Farmers Welfare, Krishi Bhavan, New Delhi, India, for his constant encouragement. We gratefully acknowledge Dr. D. P. Kothari, former Director i/c Indian Institute of Technology, Delhi, for his guidance and utmost support at every step. We also appreciatively acknowledge the help provided by Dr. Akhatar Kalam, Head of Engineering and Leader of Smart Energy Research Unit College of Engineering and Science (D524 or D332), Victoria University, Ballarat Road, Footscray 3011, Victoria, Australia. He is an enthusiastic academician and researcher. We appreciate our spouses, Mrs. Poonam Pandey and Mrs. Abhilasha, and our beloved children, Ms. Shravani Pandey, Master Tijil Kumar and Ms. Idika Kumar. xvii
They are the great source of support and inspiration, and their patience and sympathetic understanding throughout this project have been most valued. Our heartfelt special thanks go towards Springer for publishing this book. We would also like to thank those who were directly or indirectly involved in bringing up this book successfully. Last but not least, we wish to express our warmest gratitude to our respected parents Sh. Krishna Nandan Pandey and Smt. Indu Devi and the late Sh. Tara Chand and Smt. Vimlesh and our siblings for their unselfish efforts to help in all fields of life.
Characteristics of Different Systems for the Solar Drying of Crops . . . . Brian Norton
Fundamental Mathematical Relations of Solar Drying Systems . . . . . . . Stamatios Babalis, Elias Papanicolaou, and Vassilios Belessiotis
Advancement in Greenhouse Drying System . . . . . . . . . . . . . . . . . . . . . 177 Anil Kumar, Harsh Deep, Om Prakash, and O.V. Ekechukwu Part II
Design and Testing of Solar Drying Systems
Design Analysis and Studies on Some Solar Drying Systems . . . . . . . . . 199 Vinod Kumar Sharma and Cosmas Ngozichukwu Anyanwu Thermal Testing Methods for Solar Dryers . . . . . . . . . . . . . . . . . . . . . . 215 Shobhana Singh Exergy Analysis of Solar Dryers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Anil Kumar, Saurabh Ranjan, Om Prakash, and Ashish Shukla Part III
Modeling of Solar Drying Systems
Mathematical Modeling of Solar Drying Systems . . . . . . . . . . . . . . . . . . 265 Rajendra C. Patil and Rupesh R. Gawande Drying Kinetics in Solar Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 Raquel de Pinho Ferreira Guine´ and Maria Jo~ao Barroca xix
Mathematical and Computational Modeling Simulation of Solar Drying Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 Rebecca Rose Milczarek and Fatima Sierre Alleyne Numerical Techniques for Evaluating the Performance of Solar Drying Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Karunesh Kant, Atul Sharma, and Amritanshu Shukla Simulation of Food Solar Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 Ineˆs N. Ramos, Teresa R.S. Brand~ao, and Cristina L.M. Silva Applications of Soft Computing in Solar Drying Systems . . . . . . . . . . . . 419 Om Prakash, Saurabh Ranjan, Anil Kumar, and P.P. Tripathy Part IV
Environomical Impact of Solar Drying Systems
Economics of Solar Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 Deepali Atheaya Techno-economic Analysis of Solar Dryers . . . . . . . . . . . . . . . . . . . . . . 463 S. Selvanayaki and K. Sampathkumar Economic Analysis of Various Developed Solar Dryers . . . . . . . . . . . . . 495 Om Prakash, Saurabh Ranjan, Anil Kumar, and Ravi Gupta Economic Analysis of Hybrid Photovoltaic-Thermal (PV-T) Integrated Indirect-Type Solar Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . 515 Sujata Nayak and Kapil Narwal Energy Analysis of the Direct and Indirect Solar Drying System . . . . . . 529 Om Prakash, Anil Kumar, Prashant Singh Chauhan, and Daniel I. Onwude Part V
Innovations in Solar Drying
Energy Conservation Through Recirculation of Hot Air in Solar Dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545 Kamaruddin Abdullah Development and Performance Study of Solar Air Heater for Solar Drying Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 Partha Pratim Dutta and Anil Kumar Thermal Energy Storage in Solar Dryer . . . . . . . . . . . . . . . . . . . . . . . . 603 Ajay Kumar Kaviti and Harsh Deep Development of Phase Change Materials (PCMs) for Solar Drying Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 Anand Jain, Anil Kumar, A. Shukla, and Atul Sharma
Kamaruddin Abdullah Universitas Darma Persada (UNSADA), Jakarta Timur, Indonesia Fatima Sierre Alleyne United States Department of Agriculture – Agricultural Research Service, Healthy Processed Foods Research Unit, Albany, CA, USA Cosmas Ngozichukwu Anyanwu Department of Agricultural and Bioresources Engineering, University of Nigeria, Enugu State, Nigeria T.V. Arjunan Department of Mechanical Engineering, Coimbatore Institute of Engineering and Technology, Coimbatore, India Deepali Atheaya School of Engineering and Sciences, Mechanical Engineering Department, Bennett University, Greater Noida, Uttar Pradesh, India Stamatios Babalis National Center for Scientific Research “DEMOKRITOS”, Solar & Energy Systems Laboratory, Athens, Greece Jan Banout Faculty of Tropical AgriSciences, Department of Sustainable Technologies, Czech University of Life Sciences Prague, Suchdol, Czech Republic Maria Jo~ ao Barroca Molecular Physical-Chemistry Group, Coimbra University Research Center, Coimbra, Portugal Vassilios Belessiotis National Center for Scientific Research “DEMOKRITOS”, Solar & Energy Systems Laboratory, Athens, Greece Teresa R.S. Branda~o CBQF- Centro de Biotecnologia e Quı´mica Fina, Escola Superior de Biotecnologia, Centro Regional do Porto da Universidade Cato´lica Portuguesa, Porto, Portugal Prashant Singh Chauhan Department of Energy (Energy Centre), Maulana Azad National Institute of Technology, Bhopal, India
Raquel de Pinho Ferreira Guine´ CI&DETS Research Centre and Department of Food Industry, Polytechnic Institute of Viseu, ESAV, Viseu, Portugal CERNAS Research Centre, Polytechnic Institute of Coimbra, ESAC, Coimbra, Portugal Harsh Deep Department of Mechanical Engineering, Birla Institute of Technology, Mesra, Ranchi, India Partha Pratim Dutta Department of Mechanical Engineering, Tezpur University, Tezpur, India O.V. Ekechukwu Department of Mechanical Engineering, University of Nigeria, Nsukka, Nigeria Rupesh R. Gawande Mechanical Engineering Department, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, Maharashtra, India Ravi Gupta Department of Agricultural Engineering, Rajmata Vijayaraje Scindia Krishi Vishwavidyalaya, Gwalior, India Anand Jain Department of Energy (Energy Centre), Maulana Azad National Institute of Technology, Bhopal, India Karunesh Kant Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Rae Bareli, India Ajay Kumar Kaviti Department of Mechanical Engineering, Vallurupalli Nageswara Rao Vignana Jyothi Institute of Engineering and Technology, Hyderabad, India Anil Kumar Department of Energy (Energy Centre), Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh, India Rebecca Rose Milczarek United States Department of Agriculture – Agricultural Research Service, Healthy Processed Foods Research Unit, Albany, CA, USA Kapil Narwal Department of Mechanical Engineering, Manav Rachna University, Faridabad, India Sujata Nayak Department of Mechanical Engineering, Manav Rachna University, Faridabad, India Brian Norton Dublin Energy Lab, Dublin Institute of Technology, Dublin 7, Ireland Daniel I. Onwude Department of Agricultural and Food Engineering, Faculty of Engineering, University of Uyo, Uyo, Nigeria Elias Papanicolaou National Center for Scientific Research “DEMOKRITOS”, Solar & Energy Systems Laboratory, Athens, Greece
Rajendra C. Patil Mechanical Engineering Department, Bapurao Deshmukh College of Engineering, Wardha, Nagpur, Maharashtra, India Om Prakash Department of Mechanical Engineering, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India Ineˆs N. Ramos CBQF- Centro de Biotecnologia e Quı´mica Fina, Escola Superior de Biotecnologia, Centro Regional do Porto da Universidade Cato´lica Portuguesa, Porto, Portugal Saurabh Ranjan Centre for Energy Engineering, Central University of Jharkhand, Ranchi, India K. Sampathkumar Department of Mechanical Engineering, Tamilnadu College of Engineering, Coimbatore, India S. Selvanayaki Department of Agricultural and Rural Management, TamilNadu Agricultural University, Coimbatore, India Atul Sharma Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, India Vinod Kumar Sharma Department of Energy, Division for Bioenergy, Biorefinery and Green Chemistry (DTE-BBC), Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) Research Centre, Rotondella (MT), Italy Amritanshu Shukla Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Rae Bareli, India Ashish Shukla School of Energy, Construction and Environment, Coventry University, Coventry, UK Cristina L.M. Silva CBQF- Centro de Biotecnologia e Quı´mica Fina, Escola Superior de Biotecnologia, Centro Regional do Porto da Universidade Cato´lica Portuguesa, Porto, Portugal Shobhana Singh Department of Energy Technology, Aalborg University, Aalborg East, Denmark P.P. Tripathy Department of Agricultural & Food Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India S. Vijayan Department of Mechanical Engineering, Coimbatore Institute of Engineering and Technology, Coimbatore, India
About the Editors
Om Prakash received his doctorate in energy from the Maulana Azad National Institute of Technology Bhopal, India, in 2015. He was awarded scholarship during his postgraduate and doctorate programmes. Presently, he is working as Assistant Professor in the Department of Mechanical Engineering at the Birla Institute of Technology, Mesra, Ranchi, India. He has published 20 research papers in international journals and 08 papers in international conferences. He has also contributed four book chapters. He is reviewer of many reputed international journals such as the International Journal of Green Energy, Renewable and Sustainable Energy Reviews and International Journal of Ambient Energy and projects such as The Energy Report. He is working in the fields of renewable energy, energy and environment, solar energy applications, heat transfer and energy economics. Anil Kumar is presently working as Assistant Professor, Dept. of Energy (Energy Centre), Maulana Azad National Institute of Technology (MANIT), Bhopal (India) and he was researcher in the Energy Technology Research Center, Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla, Thailand from June 2015 to May 2017. He completed his B.Tech. in Mechanical Engineering followed by an M.Tech. in Energy Technology and a Ph.D. in ‘Thermal Modelling of Greenhouse Dryer’ from the Centre for Energy Studies (CES), Indian Institute of Technology Delhi, India. He has 11 years of experience in teaching and research at International/National institutes. His main areas of research interest are: solar thermal technology, distribution of energy generation, clean energy technologies, renewable energy application in buildings and energy economics. He has published four books, namely, Energy, Environment, Ecology, and Society; Fundamentals of Mechanical Engineering; Environmental Science: Fundamental, Ethics & Laws; and Advanced Internal Combustion Engine, and holds two patents. He has also published more than 105 research articles in journals and at international conferences. Presently, he is reviewer of various journals of repute. In his tenure at the MANIT Bhopal, he has supervised 05 Ph.D. and 19 master’s students. He is recipient of “Research Excellence Award 2016”: The researcher has Top 20 Publications from the Web of Science database, honoured by President, Prince of Songkla University, Hat Yai, Thailand. xxv
Concept of Solar Drying
Fundamental Concepts of Drying S. Vijayan, T.V. Arjunan, and Anil Kumar
Abstract In recent years, the postharvest losses of food and agricultural products have been reduced with the advanced preservation methods. Drying is one of the oldest preservation methods used by human for industrial and agricultural products. This is the simplest and most cost-effective method among other preservation methods. This chapter discusses about the fundamental concepts of drying such as water activity and its significance, important properties of air and the product, drying mechanism, drying curves and the performance indicators of dryer. The fundamental knowledge in drying will enable the better understanding of any drying systems. Keywords Drying • Water activity • Drying mechanism • Drying kinetics • Thin layer drying • Deep bed drying
1 Introduction Drying is one of the most commonly followed methods of preservation, for fruits, vegetables and food products. The word preservation indicates the process of extending the storage period of any product with desired quality. Food preservation is adopted mainly due to inappropriate planning in agriculture, adding value to the products and variation in nutritional values. The spoilage of the products usually occurs at various stages like harvesting, transport, storage and processing due to handling and physical, chemical or microbial damages. But most of the food products such as grains, fruits and vegetables deteriorate due to chemical or