1. COIMBATORE INSTITUTE OF ENGINEERING AND TECHNOLOGY
PERFORMANCE STUDY ON TRIPLE PASS SOLAR
DRYER FOR AGRICULTURAL PRODUCTS
Presented by
Subhash.S 710511114044
Vinothkumar.P 710511114052
Sadham Hussain.S 71051114312
Sanjeev Kumar.B 710511114313
Guided by
Mr. S.Vijayan M.E.,
Project Viva-Voce Date:- 10.04.2015
2. CONTENTS
• Overview
• Problem identified
• Objective
• Methodology
• Experimental setup
• Experimental study
• Results and discussion
• Conclusion
• references
3. OVERVIEW
• Solar energy is radiant light and heat from the sun harnessed using a range of ever-
evolving technologies and it is an important source of renewable energy which is
one of the cleanest energy source available in the earth.
• Solar drying uses the sun as direct source of energy to dry the crops thermally.
• In direct solar drying the agricultural products are dried by placing in products
under the glass plate which is directly exposed to sunlight but it has several
disadvantages.
• The disadvantages of this type is overcome by the indirect type forced convection
solar drying.
4. PROBLEM IDENTIFICATION
• Solar dryers with flat plate collector have a disadvantage that it
has a less heat transfer rate of air.
• The availability of the system for operation i.e. solar radiation
available only in the day time.
• The intermittent property of sun’s radiation may lead to
improper drying or detoriation of quality of the product.
• Direct exposure of the product to the sun radiation results in
colour loss, change in the nutritional values etc.,
5. OBJECTIVE
• Improving the heat transfer rate of air by introducing porous
medium in the path of air.
• The products to be dried in a constant drying rate by
incorporating a thermal stabilizing medium like sand.
• Excessive thermal energy can be stored in the thermal storage
medium for later use.
• The drying of the agricultural products quality can be
improved by drying it inside the chamber.
6. METHODOLOGY
• Design of an experimental setup
– Selection of heat transfer improvement method
– Selection of thermal storage medium
• Development of a triple pass solar dryer with 2 m2 aperture area.
• Selection of the drying products
• Study the performance
• Results and discussions.
7. EXPERIMENTAL SETUP
• The schematic of the solar dryer consisting of a flat plate collector, drying
chamber, blower and a circulation fan.
• An aluminum sheet painted matte black is used as an absorber plate to
absorb incident solar radiation.
• A plain window glass is used as transparent cover to avoid heat losses at
the top.
• The collector air channel depth is 20 mm and the space between the
absorber to the transparent glass cover is 25 mm.
• The space between the bottom glass cover and the desiccant bed is 50 mm.
9. DESIGN AND FABRICATION OF DRYING
SYSTEM
• The collector consists of three passes
with the turbulent flow this increase the
efficiency of the collector.
17. PROCESS OVERVIEW
Pretreatment of the product
Loading the product
Measuring the various factors such as temperature, relative humidity and
solar intensity for a regular interval of time.
Drying is continued until the product attaining equilibrium moisture
content.
Unloading the product.
Measure the amount of moisture removed.
18. EXPERIMENTAL STUDY
• Experiments were conducted on drying of mint leaves, to study the effect of drying as
well as the climatic and operational parameters on the dryer performance.
• The hot air from the solar flat plate collector was forced through the grain bed and left
through the exit.
• To estimate the system performance temperature, relative humidity, weight loss of
drying product and solar intensity were recorded at 1 hour interval time.
• The drying process was continued until the product achieved its equilibrium moisture
content.
• The initial and final moisture content of the drying products were determined by the
oven method.
22. EXPERIMENTS CONDUCTED
• PRODUCT : BITTER GUARD
• PRETREATMENT : The bitter guards are washed in the water and it is
sliced up to 2mm thickness and loaded on the trays.
• By changing the thickness is from 2mm – 5mm the performance of the
system is studied.
• Each tray is loaded with 950 gms of bitter guard and the experiment is
carried out.
30. PERFORMANCE EVALUATION
• The above graph shows the moisture content removal between the natural
drying and the indirect type forced convection solar drying.
• The heat transfer rate of the solar drying system is higher than the natural
drying.
• The amount of moisture content removal rate in triple pass indirect type
solar drying is comparatively higher than the direct solar drying.
• The time taken for drying the product inside the system is 5 hours while
the natural drying requires 7 hours.
• 85% of moisture content is removed efficiently with the help of the system.
31. ADVANTAGES
• This Solar Air Dryer reduces the cost compare to other conventional
process.
• It is simple in design and fabrication.
• The agricultural products can be preserved long time.
• The drying period is less.
• We can minimise the human power.
• Economically it is suitable for all agricultural commercial uses.
32. CONCLUSION
In this project work a triple pass indirect forced convection solar
dryer was designed and developed with low cost material and various
agricultural products such as mint leaves, potato, and bitter guard are dried.
The initial moisture content of 92.8%, 85% and 90.7% of the products
mint, potato and bitter guard has been reduced to 7.1%, 15% and 9.3%
respectively with the drying period of 4 hours, 5 hours and 6 hours. The
maximum thermal efficiency of the collector is noted as 58.48% with a long
time energy storage.