Sun drying of agricultural products in the open air is the traditional method
employed in most of the developing countries. A new system which concerns about the
drying process of Cocos nucifera (coconut) is introduced. This project mainly focuses to
design a sophisticated monitoring system for hybrid dryer unit (Solar and biomass) of
coconut (Cocos Nucifera).The system consists of : heating unit, air blower unit, coconut
container and biomass unit. Heating unit is designed to accept electric input . The electric
supply is to heat the coil in the heating unit.
The system consists of a container in which the coconuts, cut into pieces are
placed. With the help of the air blower the hot air produced is passed for several hours
into the chamber which is kept rotating for uniform spreading of heat. The optimum
temperature required for drying the coconut is 700C-750C. Temperature is maintained at a
constant level through out the process. Now with the hot air passed uniformly around the
coconut, the moisture present in the coconut gets absorbed. The pulp gets shrinked and
becomes easy to remove. After few hours of heating the pulp again continuously, the pulp
is ready for the extraction of coconut oil. The hot air (exhaust) is passed out through the
outlet.
Monitoring the temperature, humidity, mass hot air flow and weight of the
coconut pulp are very important to get good quality of pulp. If variable temperature is
applied the quality of product will be affected. We require a monitoring system for
temperature, humidity, mass hot air flow and pressure in side the dryer unit. This is
monitored by using Lab VIEW8.2 for coconut drying process.
The application of dryers in developing countries, reduce losses and significantly
improve the quality of the dried product when compared to the traditional means of
drying such as open sun drying. Appropriate use of these sources in drying provide
reduction of drying time and specific improvement of the product quality in terms of
colour, texture and oil content in comparison to open sun drying.
INTRODUCTION
Sun drying is still the most common method used to preserve agricultural
products in most tropical and subtropical countries. However, being unprotected from
rain, wind-borne dirt and dust, infestation by insects, rodents and other animal, products
may be seriously degraded to the extent that sometimes become inedible and the resulted
loss of food quality in the dried products may have adverse economic effects on
domestics and international markets. The most important reasons for using the dryer are
popularity of dried products is longer shelf-life, product diversity as well as substantial
volume reduction. This could be expanded further with improvements in product quality
and process applications. Conventional fuel operated driers are more efficient than open
sun drying, provide uniform high quality dried product, with many more advantages, but
in spite of all these favourable points, such units are beyond the reach of rural people
with limited product volume and financial resources. So we design a system which suits
to the small scale farms and also excellent monitoring system.
OBJECTIVES
• To design a hybrid ( solar, biomass ) dryer unit for coconut
• To minimise the time of drying of coconut
• To reduce the man power
• To increase the compactness of the drying process
EXISTING PROCESS
The existing process in the drying of coconut in the open air is the traditional
method employed for most of the developing countries. Generally the process of drying
coconut takes around ten days. This drying process of the coconut involves four stage
processes
1. I stage-open drying in atmospheric air
2. II stage-shell removal process.
3. III stage-pulp drying.
4. IV stage-oil extraction process
Finally the pulp is ready for extraction of coconut oil.
I -STAGE (TWO DAYS PROCESS)
In the first stage process the coconuts are cut into two halves .Then the coconuts are
dried in open sunlight .During this drying Process the moisture content of the coconuts
gets absorbed .After two days the pulp gets shrinked inside as shown in the figure.1.
Result of two day process (pulp is shrinked)
Figure .1. Open Drying Process
Weight analyze of one sample= 110gm
II -STAGE (ONE DAY PROCESS)
Due to the absorbance of moisture content in the coconut the pulp gets shrinked
so that that the pulp is easily removed from the outer shell as shown in the figure.2.
(Outer shell is removed)
Figure. 2. Shell Removal Process
Weight analyze of one sample= 65gm
III -STAGE (TWO DAYS PROCESS)
Then the pulp is again dried in sunlight to remove the moisture Content. Due
to that weight reduction of coconut pulp takes place as shown in the figure 3 &4.
(Result of five day process)
Figure. 3. Shell Removal Process
Weight analyze of one sample= 60gm
III -STAGE -FINAL CONDITION TO BE-(FIVE DAY PROCESS)
(Result of ten day process= (5+5))
Figure. 4. Shell removal process
Weight analyze of one sample= 55gm
IV –STAGE PROCESS
The moisture content of the coconut is reduced and the pulp is ready for
Oil extraction process as shown in the figure 5.
Figure. 5. Oil extraction process
WEIGHT AND TIME ANALYSIS
Calculation of weight and time of the sample for the existing method below.
Table.1. Weight and Time Analysis
stage process weight(gm) time(hr) days
1-stage 110 48 2
2-stage 65 24 1
3-stage 60 48 2
3-stage 55 120 5
Total 240 10
stage process
0
20
40
60
80
100
120
140
1-stage 2-stage 3-stage 3-stage
stage levels
analysis
weight(gm)
time(hr)
Figure.6.Weight Vs Stage Levels
DISADVANTAGES OF EXISTING PROCESS:
• Time consumption is more period of 10 days
• More labors are required.
• Productivity is mainly affected in rainy season and at night times.
• It needs large work area.
• Insect infestation and the contamination of dust.
• Average of temperature of atmosphere=35o C
CLIMATIC CONDITION IN TAMIL NADU
The climatic condition of Tamil Nadu (Chennai) is given below. This
climatic condition is more or less equal to the climatic condition of our city Erode, Tamil
Nadu.
Table .2.Climatic Condition in Tamil Nadu (Erode)
MADRAS
Month
Rainfall(mm) Temperature(Celsius)
Average
monthly
Ave no of
days with
1mm
Average daily
Lowest
recorded
Highest
min max recorded
Jan 27 2 20.4 28.8 15.8 33.1
Feb 34 1 21.6 30.7 15.8 35.8
Mar 4 0 23.5 33.2 18.0 38.5
Apr 12 1 26.2 35.6 21.4 41.9
May 39 2 27.7 38.0 21.4 44.1
Jun 71 8 27.4 37.4 20.1 42.7
Jul 121 10 26.0 35.3 21.2 39.9
Aug 138 11 25.6 34.5 21.3 38.5
Sep 161 10 25.3 34.0 21.1 38.4
Oct 373 12 24.4 31.9 19.4 36.5
Nov 409 12 22.7 29.5 17.8 33.2
Dec 152 7 21.5 28.4 16.8 31.8
Graphical representation of Temperature Vs Interval of Months
Figure .7.Temperature Vs Interval of Months
The graph above states that the temperature level is not uniform throughout the month.
The average of temperature in all months doesn’t exceed more than 40oc. This is
available temperature for farmers for drying the coconut. But the optimum temperature
required for drying the coconut is 70oc-75oc as published in one journal Sujata Jena, H.
Das,” Modelling for vacuum drying characteristics of coconut presscake” Department of
Agricultural and Food Engineering, Dairy and Food Engineering Laboratory, Indian
Institute of Technology,Kharagpur 721302, WB, India
climatic condition
0
5
10
15
20
25
30
35
40
45
50
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
interval of months
temperature
minimum temperature(degree celsius)
maximum temperature(degree celsius)
climatic condition
0
50
100
150
200
250
300
350
400
450
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
interval of months
r a i n f a l l
Rainfall(mm)
Average
monthly
Rainfall(mm)
Ave no of
days with
Figure 8. Temperature Vs Interval of Months
The figure 8. States the conditions during rainy seasons. The amount of maximum
rainfall recorded is 350-400mm (average) which majorly affects the drying process. So
the productivity during this season is affected very badly.
BLOCK DIAGRAM OF OUR MONITORING SYSTEM
SOLAR PANEL
The system consists of single glazed solar cabinet drier mounted on a rock slab.
The rock slab is placed on a chamber made of bricks. The top glass surface is inclined at
an angle of 28.5° to maximize the capture of solar radiation.
SOLAR
CELLS
BATTERY
CONVERTER
AIR BLOWER
RELAY COIL (OF
ELECTRICAL SUPPLY)
HEATING
UNIT
BIO MASS
UNIT
OUTLET AIR
SOLAR
PANNEL
HEATING
UNIT
AC MOTOR
(FOR
ROTATION)
ELECTRICAL
CURRENT
CONTAINER
(Samples are
placed)
AIR BLOWER
UNIT
FURNACE
LAB VIEW8.2
The power got from the solar energy is stored in the battery during day time. The
converter set up is built to convert Direct Current to Alternate Current to heat the coil.
BIOMASS UNIT:
The biomass process is same as the real time existing process. The waste material
of cow dung is mixed and stirred in one chamber. This mixture passes through a pipe line
through a large closed chamber. Usually the chamber is closed by a conducting with
conducting material (i.e.) iron at the top .when the iron metal is exposed to sunlight the
internal pressure inside the closed chamber increases and it produce flue gas called
methane (CH4). The methane gas is passed into a channel where a furnace is placed.
When the furnace is lightening it produce a hot gas. This hot gas is completely sucked by
the air blower and passed in to the container where the coconut samples are placed.
Block Diagram of Electrical Assembly
BIO GASS
CHAMBER
AIR BLOWER
PIPE LINES
FURNACE
EXHAUST
TEMPERATURE
CONTROLLER
Power Supply
THERMOSTAT
TEMPERATURE MONITORING SYSTEM USING LAB VIEW8.2:
`
Our project provides the ultimate solution to the temperature monitoring system
to the drying process and to maintain the uniform temperature into the dryer. Not only
temperature, initial weight, final weight (after drying), drying time, mass air flow and
LAB VIEW8.2
Solar panel
Air Blower
Container
Heating
Unit
humidity also has been considered to design a sophisticated monitoring system (using
Lab VIEW8.2) for coconut drying process.
National Instruments products (Hardware and Software) used in this Application are
• LabVIEW 8.2
• SCXI-1112 thermocouple input module
• SCXI-1520 strain gauge input module
• LabVIEW for windows SCXI-1600/SCXI-1000 bundle
• We measure the temperature of the container (system) using RTD, for monitoring
and controlling the temperature using LabVIEW, thermocouple module(SCXI-
1112) is employed.
• Similarly for monitoring the weight of testing samples (coconut) the strain gauge
module (SCXI-1520) is employed
The benefits of using Virtual Instrumentation are
• Flexibility
• Reduces cost and preserves investment
• Plug-in and network hardware
• Open development environment(Lab VIEW provides the tools required for most
application)
• Multiple platforms
MECHANCICAL DESIGN OF CONTAINER
The line diagram of the container is designed as shown in the figure .The
container is cylinder in shape .One end of the container is connected to the inlet. The hot
air from the air blower passes through the inlet. A pulley is connected at the outlet in
which an ac motor is connected .ac motor is used for uniform rotation of the container
.the exhaust gas passes through the outlet. The coconut samples are placed inside the
container.
Container Specification
Capacity : 50 kg
Length : 44 cm
Diameter : 38.6 cm
Material : Mild Steel
Thickness of sheet : 2.5 mm
Opening door size : 20.5X25.5 cm2
MECHANICAL DESIGN OF HEATING UNIT
AC
MOTOR
INLET
OUTLET
FLANGE
PULLEY
BEARING
OPENING
The proE model of the heating unit is designed as shown in the figure. The
heating unit is used to heat the heating coil .A Heating coil is attached with the one feet
rod. The outlet of the heating unit is connected to the air blower. So the air circulation
inside the heating unit occurs. When electric power is given to the heating coil, the
heating element gets heated according to the temperature set in the regulator.
Heating Unit Specification
Power supply : 230v, single phase ac supply
Temperature Control : 0o to 100oc
Relay : 220v
Energy Consumption : 1kwh
Material : copper rod
Internal Diameter : 1cm
External Diameter : 2cm
Length : 30cm
MECHANICAL DESIGN OF AIR BLOWER
The blower setup is designed as shown in the Figure is used to suck the heated air
and distributed at faster rate into the container. Basic designs are modified, depending
upon the nature of gas to be handled. Special blowers, capable of handling different gases
are used. The air vent dimension was calculated by using the eq (1).Material of
construction and constructional details vary to meet different gas requirements. In this,
the air blower is made of aluminum material
Av = Va/Vw eq (1)
Where Av is the area of the air vent, m2,
Vw wind speed, m/s.
Av= (
D2)/4
It implies D=2 (Av/
)
D=required air vent diameter in m
Air Blower Specification
Power Supply : 230V, Single Phase ac Supply
Energy Consumption : 80 watt
Material : Aluminium alloy
Inlet : Axial inlet, 7.5cm
Outlet : Radial outlet, 5cm
PULLEY SPECIFICATION
DRIVEN PULLEY
Diameter : 20 cm
FOLLOWER PULLEY
Diameter : 4.2 cm
AC MOTOR SPECIFICATION
Power Supply : 230V, Single Phase ac Supply
Motor Speed : 1200 rpm
Starting torque : 200 to 400% of rated load
Starting current : 450 to 575% of rated current
Efficiency : 75% of rated speed
BELT DRIVE SPECIFICATION
Type : Open Belt Drive
Specification : V-belt drive
Length of Belt Drive : 80 cm
ELECTRICAL DESIGN
Power Supply Unit
The input capacitor is used to maintain a stabilized DC supply to the input
terminal of the regulator.It can be selected using the formula
C = IL x 6 x 10^ (-3) / (dV)
Where, IL = maximum load current
dv = input voltage to the capacitor
Il (max) = 750 ma
C = 750 mA x 6 x 10 ^(-3)/5
C =1000 micro farad.
FABRICATION OF THE PROJECT
Mechanical Assembly
The prototype of the model is designed as shown in the Figure .The dryer system
consists of three parts, they are heating unit, air blower unit and coconut container.
Heating unit is designed to accept electrical input. The electric supply is used to heat the
coil in the unit. The optimum temperature required for drying the coconut is 700-750C.
This optimum temperature is easily produced by electric current. The prototype of system
consists of a container in which the coconuts, cut into pieces are placed. With the help of
the air blower the hot air produced is passed for several hours into the chamber which is
kept rotating for uniform spreading of heat. The velocity of air flow is calculated using eq
(2).Temperature is maintained at a constant level throughout the process. Now with the
hot air passed uniformly on the coconut, the moisture present in the coconut gets
absorbed.
The pulp gets shrinked and becomes easy to remove. The pressure inside the
container is calculated using eq (3).After few hours of heating again continuously, the
pulp is ready for the extraction of coconut oil. The hot air (exhaust) is passed out through
the outlet. The samples were weighed at different time interval during day and night. The
percentage of weight loss of the sample is calculated using eq (4).
During rainy season or at night times where solar energy is not available the
electrical heating element can be used. The system is predestined for application on small
farms in developing countries due to its low investment. In normal method of drying
coconut is a time consuming process and large work area is needed for open drying. This
dryer, does not affect the productivity in rainy season, reduces time from weeks to several
hours, needs only less work space, utilizes natural resources, cut the manpower
requirement to a certain extent and pollution free solution to the oil mills. Also it does not
affect the quality and quantity of the oil. The calculations used for the prototype of the
model are given below.
Velocity = Va/A eq (2)
Va = volumetric flow rate m3/sec.
The pressure difference across the coconut container will be solely due to the density
difference between the hot air inside the dryer and the ambient air. Air pressure can be
determined by equation given by Jindal and Gunasekaran (1982):
P = 0.00308 g (Ti- Tam) H eq (3)
Where: H is the pressure head m; P is the air pressure, Pa; g is the acceleration due
gravity, 9.81m/s2; Tam is the ambient temperature, C.
Percentage of weight loss (W)
W= (Wi-Wf)/Wf x100 eq(4)
Wi=initial weight in kg
Wf=final weight in kg
OUR PROCESS OF ANALYSIS:
The experimental setup has been tested at Kongu Engineering College, India as
Shown in the figure .Different amount of coconut pulps are taken to the test. For our
analysis 50kg of coconut pulp has been taken for the analyses.
In Open drying method, It takes 240 hours (in the month of June July) to get
required condition for oil extraction. After get drying the weight has been reduced to
32kg. The average temperature is 30-35°C. During night time, the temperature gets low.
In open drying it occupies large work space.
The proposed system is shown in figure . As per the system the 50kg pulp requires
one and half hour to remove the outer shell. Another 5 hours to get dry to meet required
parameter. Only seven hours need to complete the process. Optimum temperature 70-
75°C is maintained inside the container. Uniform temperature is maintained during entire
process. Process can be done at several batches. It requires less space only.
PHOTOGRAPHIC VIEW OF THE PROJECT:
Design of hybrid dryer for cocos nucifera (coconut)
CONTAINER AIR BLOWER
HEATING UNIT PULLEY (SIDE VIEW)
SOLAR PANEL
ANALYSES OF THE PROCESS:
Table 3. Design conditions and assumptions
Location Erode
Crop COCOS NUCIFERA
Drying period April to June
January to december
Drying per batch(5 hr /batch) 50kg of coconut
Initial weight 50 kg
Final weight (after drying) 32.8kg
Ambient air temperature, Tam
Drying time(sunshine hours)td
35oc for July
Maximum allowable temperature, Tmax 75oc
Wind speed 11m/sec
Our experimental results are shown below:
GRAPH 1
TIME(hr) TEMPERATURE(degree Celsius)
2.42PM 30
2.57PM 46
3.01PM 50
3.06PM 56
3.08PM 58
3.11PM 62
3.18PM 68
3.22PM 70
3.28PM 70
3.35PM 70
3.45PM 70
3.49PM 70
TEMPERATURE VS TIME
0
10
20
30
40
50
60
70
80
2.42PM 2.57PM 3.01PM 3.06PM 3.08PM 3.11PM 3.18PM 3.22PM 3.28PM 3.35PM 3.45PM 3.49PM
TIME(hr)
TEMPERATURE (deg
celcius)
TEMPERATURE
GRAPH 2
TIME(hr) WEIGHT (kg) TEMPERATURE(degree Celsius)
2.42PM 50 30
3.11PM 49.5 62
3.31PM 49 70
3.42PM 48.7 70
4.15PM 48 70
4.25PM 40 70
4.52PM 39.5 70
5.15PM 38.9 70
5.45PM 37.8 70
6.15PM 36.4 70
6.45PM 34.9 70
7.15PM 33.5 70
7.45PM 32.8 70
PROCESS ANALYSIS
0
10
20
30
40
50
60
70
80
2.42PM 3.11PM 3.31PM 3.42PM 4.15PM 4.25PM 4.52PM 5.15PM 5.45PM 6.15PM 6.45PM 7.15PM 7.45PM
TIME
ANALYSIS
WEIGHT (kg)
TEMPERATURE(degree celcius)
PHOTOGRAPHIC VIEW OF LabVIEW 8.2 CONTROL:
Temperature monitoring using Lab VIEW
Front panel of temperature monitoring
BLOCK DIAGRAM OF TEMPERATURE MONITORING:
Block diagram of temperature monitoring
THEMOCOUPLE MODULE USING LABVIEW 8.2
STRAIN GUAGE MODULE USING LABVIEW 8.2
RESULTS AND DISCUSSION
Capacity and drying times with a single layer of specified length and thickness, 50
Kg of coconuts were used for study. Moisture present in the product with drying period in
one of the trials of the full load drier is 50 kg .In open sun drying it was 240 hours for
drying of the same product. The dryer produces 90% efficiency in time saving. It uses
hybrid power solar and electric. Even if heater gets off, the same temperature can be
maintained for half an hour. The pulsed time slot may set to on and of the heater, So that
the power can be saved more. It requires low man power. Uniform drying condition is not
given to coconut pulp. So quality of pulp is affected. Overall the performance is
improved to 40% compared to the present process.
As per the discussions this project provides an ultimate solution to the drying
process and also excellent monitoring of multiple parameters for this dryer. It provides a
complete system to the entire process of drying. It also can be extended to other
agricultural products with little modifications.