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Solar drying technology concept, design, testing, modeling, economics, and environment

Green Energy and Technology

Om Prakash
Anil Kumar

Concept, Design, Testing, Modeling,
Economics, and Environment

Green Energy and Technology

More information about this series at http://www.springer.com/series/8059

Om Prakash • Anil Kumar

Solar Drying Technology
Concept, Design, Testing, Modeling,
Economics, and Environment

Om Prakash
Department of Mechanical Engineering
Birla Institute of Technology, Mesra
Ranchi, Jharkhand, India

Anil Kumar
Department of Energy (Energy Centre)
Maulana Azad National Institute of Technology
Bhopal, Madhya Pradesh, India

ISSN 1865-3529
ISSN 1865-3537 (electronic)
Green Energy and Technology
ISBN 978-981-10-3832-7
ISBN 978-981-10-3833-4 (eBook)
DOI 10.1007/978-981-10-3833-4
Library of Congress Control Number: 2017949696
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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
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


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:

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,

Akhtar Kalam

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

Trilochan Mohapatra



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
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
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
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
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



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
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
We appreciate our spouses, Mrs. Poonam Pandey and Mrs. Abhilasha, and our
beloved children, Ms. Shravani Pandey, Master Tijil Kumar and Ms. Idika Kumar.



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


Part I

Concept of Solar Drying

Fundamental Concepts of Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
S. Vijayan, T.V. Arjunan, and Anil Kumar


Solar Drying Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jan Banout


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



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,
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
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,
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,
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.

Part I

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

S. Vijayan • T.V. Arjunan
Department of Mechanical Engineering, Coimbatore Institute of Engineering and Technology,
Coimbatore 641109, India
A. Kumar (*)
Department of Energy (Energy Centre), Maulana Azad National Institute of Technology,
Bhopal 462003, Madhya Pradesh, India
e-mail: anilkumar76@gmail.com
© Springer Nature Singapore Pte Ltd. 2017
O. Prakash, A. Kumar (eds.), Solar Drying Technology, Green Energy and
Technology, DOI 10.1007/978-981-10-3833-4_1


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