International Journal of Research In Science & Engineering
Volume: 1 Issue:3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
SOLAR DRYER SYSTEM (A REVIEW PAPER)
Prof.S.S.Bhansali1 , Sonali nagargoje 2 , Suraj Wasade 3 , Amol Kanwale 4
1
prof, Mechanical Engineering, JDIET, Yavatmal, Maharashtra, India, [email protected]
Student, Mechanical Engineering, JDIET, Yavatmal, Maharashtra,India,sonunagargoje1993@gmail
3
Student, Mechanical Engineering, JDIET, Yavatmal, Maharashtra, India, [email protected].
4
Student, Mechanical Engineering, JDIET, Yavatmal, Maharashtra, India,[email protected]
2
ABSTRACT
The solar drying system utilizes solar energy to heat up air and to dry any food substance. The most of the
researche have found for solar drying process i.e. on the flat plate, direct solar dryer system, Solar cabinet dryer,
Glass roof solar dryer, Indirect natural convection solar dryer with chimney. This paper presents the design and
construction of a solar food dryer. This system runs by force convection, free convection method for drying multiple
fruits. The time, intensity, temperature and the moisture contain in the fruits were calculated for grapes. In this type
of solar air heater glass tube and flat glass plate was used for absorption of reflected solar radiation .This system
will maintain the quality of grapes.
KEYWORDS: Grapes; force convection; free convection solar dryer chamber etc.
----------------------------------------------------------------------------------------------------------------------------1. Introduction
Fruits and vegetables constitute a major part of the food crops in developing countries. Drying is one of the seasonal
methods which is used for preserving the fruits. Many varieties of fruits are seasonal and most of them are
consumed in their dried form to a long time. This has been made possible by the process of drying Grape is world‟s
largest fruit crops in India. The world production of grapes is presently more in In dia[1]. Drying the grape produces
raisins.
India receives an enormous amount of solar energy: on average, of the order of 5 kWh/m2 day for over 300
days/year [8]. This energy can be used for electrical applications. Drying, which is most commonly used for drying
agricultural products, it remove the moisture within the product by heat and its subsequent evaporation from the
product. Thus, drying involves simultaneous heat and mass transfer [3].
2. Direct type solar dryers
In direct solar dryer system solar radiation directly passes through the glass plate which is transparent and is used for
drying the grapes.
2. 1. Solar cabinet dryer
In this System The Simple Wooden Box[4] Having The Transparent Glass Cover Inside The Bottom Side
Of Solar Dryer Has Painted With Black Color For Drying The Grapes Which Are Placed On Aluminum
tray which has shown in figure[1].This system is use to remove the more moisture from the grape. This
type of dryer covers the whole width of the printing area. Engineered as an enclosed cabinet it contains a
bank of highly efficient Infrared lamps, tunnels for fresh air and channels to extract the hot air to the
outside. IR drying power is automatically controlled according to the print speed. The system consists of
a drying cabinet, a hot air exhaust fan, a control cabinet, an operator panel, a speed sensor and a heat
shield and general the specification of solar dryer has shown in table[1].
IJRISE| www.ijrise.org|[email protected] [21-27]
International Journal of Research In Science & Engineering
Volume: 1 Issue:3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
Web width:
 20.5” (520
Web speed:

500 ft/min (150
m/min)

1000 ft/min
(300 m/min

1500ft/min (450
m/min)
mm
 29” (740
mm)
 38” (960
mm)
Fig[1]:cabinet dryer
Table-1: specification of carbonate dryer
2. 2 . Foldable solar grape dryer
In this solar dryer is covered by the two incline glass roofs as shown in figure [2], in which one roof has provided
the longitudinal slot for removing the moisturized air. Due to this fresh air can be sucked because of the partial
vacuum is created in the dryer. The fresh atmospheric air is sucked. The grapes are placed on the trays which are
heated due to the solar radiation [1].
Fig[2]:Foldable type solar dryer
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International Journal of Research In Science & Engineering
Volume: 1 Issue:3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
3. 0 Indirect solar drying of grapes
In indirect solar drying system the circulation of air can be classified as natural circulation & force convection
method.
3. 1. Natural circulation type
In this type of the atmospheric hot air is passes through the natural convection for drying the
grapes and for removing moisture.
3. 1. 1. Indirect type conventional solar dryer
This solar dryer is used for air heating and drying the chamber in which the grapes are put on the tray as shown in
figure[4].the transparent cover has provided with trans ferring foil cover for avoiding from the dust and rain .This
solar collector collects the energy and heats the air entering through an inlet then heated air enters the drying
chamber through beneath the tray and flows upwards through the trays where the grapes are placed. Then moist air
goes out of the opening provided at the top. Ventilation has provided by natural convection inside the collector [2].
3. 1. 2. Indirect type natural convection solar dryer chimney
In indirect natural circulation solar dryer system, is shown in figure[3]. It consist collector, drying chamber with
a chimney. The solar collector has a black painted copper plate for absorption. A glass covers which is fixed over
the copper plate with an air gap for entering the air. An insu lation layer is provided at the bottom to minimize heat
losses . The drying chamber made of wood is fixed with a black painted galvanized iron with cylindrical chimney.
The chimney has the buoyant force for imposing on the air stream, it provides a greate r air flow velocity. Loading
and unloading takes place through the door which is one side of the drying chamber [2].
Fig[3]:Indirect type natural convection solar dryer chimney
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International Journal of Research In Science & Engineering
Volume: 1 Issue:3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
3. 1. 3. Indirect natural convection solar dryer with chimney and storage material
Fig:[4] Indirect natural convection solar with chimney and storage material
An indirect natural convection solar dryer with chimney and storage material used for drying grapes is shown in
figure[4]. With the use of flat plate solar air heater which is coupled to a drying chamber the solar dryer is mainly
done. The solar air heater uses a matte black painted copper plate as an absorber glass has covered with copper plate
having the air gap for minimizing the heat losses the insulated wooden box has filled with saw dust. The sand is
used for producing the heat after sunset. The dryin g chamber made of wood is fixed with a matte black painted
galvanized iron cylindrical chimney at the top .The tray are made aluminium wire for holding the grapes. The drying
trays are loaded and unloaded through the door [3].
3. 2. Forced type circulation
In these types of solar dryers air is forced into or out of the drying chamber using a blower or fan which is
electrically or mechanically operated.
3. 2. 1. Solar air flat plate collector
Figure-[5] shows a solar air flat plate collector with obstacles, it is an indirect blow-dryer system that operates in the
forced convection method. The system has a solar air flat plate collector acting as a hot air maker, fan and also the
microcontroller is used microwave drying is an energy-efficient drying method. Where the amount of microwave
energy is determined by the ratio of “ON cycles” to “OFF cycles.”The solar collector consist a polycarbonate and
transparent cover at the top, the absorber plate has made from an aluminium sheet with painted black and obstacles
fixed to a thin plate are placed with an insulator of polystyrene. The collector is placed at an inclined angle of 45 o .
IJRISE| www.ijrise.org|[email protected] [21-27]
International Journal of Research In Science & Engineering
Volume: 1 Issue:3
e-ISSN: 2394-8299
p-ISSN: 2394-8280
Due to the presence of obstacles maximum heat gains which fix between the cover and insulator. This maximises the
system efficiency with minimum load losses [3].
Fig [5]: Solar air flat plate collector
Figure-[5] shows a solar air flat plate collector with obstacles, it is an indirect blow-dryer system that operates
in the forced convection method. The system has a solar air flat plate collector acting as a hot air maker, fan and also
the microcontroller is used microwave drying is an energy-efficient drying method. Where the amount of microwave
energy is determined by the ratio of “ON cycles” to “OFF cycles.”The solar collector consist a polycarbonate and
transparent cover at the top, the absorber plate has made from an aluminium sheet with painted black and obstacles
fixed to a thin plate are placed with an insulator of polystyrene. The collector is placed at an inclined angle of 45 o .
Due to the presence of obstacles maximum heat gains which fix between the cover and insulator. This maximises the
system efficiency with minimum load losses [4].
3. 2. 2. Solar multiple layer batch dryer
This solar dryer has a flat plate solar air collector, a blower and a multiple layer batch dryer as shown in figure[6].
The air collector has a transparent foil cover and a black corrugated metal absorber. Air is sucked underneath the
absorber for avoiding dust contamination on the absorber surface. A centrifugal fan is placed between the collector
and the dryer is used to suck air. Trays have made of wire mesh and has installed in a container which serves as a
multiple layer batch dryer. During the drying process the initial air flow rate is a little high in the dryer and later it is
reduced [1].
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International Journal of Research In Science & Engineering
Volume: 1 Issue:3
Fig[6] : Solar multiple layer batch dryer
e-ISSN: 2394-8299
p-ISSN: 2394-8280
Fig:[7]Indirect type solar fruit and vegetable dryer
3. 2. 3. Indirect type solar fruit and vegetable dryer
In this type system the solar radiation solar rays are absorbed th rough the transparent glass flat plate where the
solar radiations are absorbed indirectly. Where the glass trays can loaded or unloaded from the front type of solar
chamber as shown in figure[7]It is found that the air heater operating at low temperatures is able to heat air from 55
to 60 C, while the medium temperature air heater is able to heat air from 75 to 80C at noon [2].
3.2.4. Dish type solar dryer system
A study is conducted to develop an efficient drier in the form of a dish type solar air heater that could dry
grapes. Two air flow rates i.e. first natural and second convective air flow rates at different day timings. It shows
result flow rates significantly (P < 0.001) affected efficiency of solar air heater. It‟s efficiency increases from 12
percent at natural to 24 percent and 35percent at convective air flow rates is 0.21 and 0.28 kg per second,
respectively. Grapes are dried at temperature of 50°C and less than20 % humidity. Air flow rate of 0.27 kg per
second was given for drying in drying chamber and grapes have dried less than a moisture content of 9 percent. It is
observed that in figure-[8] grapes were dried in 24 hours by dish type solar air heater‟s drying chamber. The study
has concluded that parabolic dish type solar air heater for drying grapes should be operated at high flow rates to
achieve high efficiency at less time [2]. It also maintained the quality of grapes and reduces losses from pest attacks.
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International Journal of Research In Science & Engineering
Volume: 1 Issue:3
Fig[9]:concentrated
parabolic
Fig[8]: Dish type solar dryer system
solar
e-ISSN: 2394-8299
p-ISSN: 2394-8280
dryer
3.2.5 Parabolic plate solar dryer system:
In galvanized parabolic plate the solar radiations are collected by parabolic plate where the solar radiations are
reflected through the copper tube and air is heated which is shown in figure[9] .the atmospheric air is sucked by the
blower and blowers runs on the PV cell[14]. It is useful for the household application And also useful for industrial
application.
4. CONCLUS ION
It has been established that solar drying of grapes in indirect solar system is more economical and beneficial than the
direct solar dryer system It is also applicable for the industrial, agricultural and also useful in the household
purposes. In order to encourage small and marginal farmers to use solar dryers, it is economical ,simple eco -friendly
solar dryer system for the multipurpose drying grapes and multi fruits.
5. ACKNOWLEDGEMENT
We are highly indebted to our head of department PROF. Dr.A.B.BORADE for their guidance and
constant supervision. We are also thankful to our guide PROF.S.S.BHANSALI who gave us lo t of courage during
this paper as well as for providing necessary information regarding the seminar and for t heir support in completing
the paper.we would like to express my gratitude towards all the member of mechanical department for their kind co operation and encouragement which help me in completion of this paper..
6.REFERENCES
[1] S.P.Singh, K.S.Jairaj* , K.Srikant, „„the development of solar dryers used for grape drying‟‟,2011
[2] Mohmand Hani , ‘‘drying of the grape using dish type solar air heater’’,2011.
[3] R.Manikanta,K.N.Sheeba and S.Jaisankar, „„Green house solar dryer‟‟,Augest2012vol6:1554.
[4] N.Rajeshwari and Ramaligam, „„Low cost material used to construct the solar box‟‟,April 2012,4(3):1476-1482.
[5] R.Vidhyasagar Raju,R.Meenakshi Reddy,E.Redd , „„Design and fbrication of solar dryer‟‟,vol-3,Issues6
November 2013.
[6] Prof.M.Ramkrishnarao, „„Invotive solar food processingtechnology‟‟,Augest 2014
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