AN ORAL PRESENTATION ON DESIGN AND CONSTRUCTION …...ASTM (2005). ³ Standard temperature for...
Transcript of AN ORAL PRESENTATION ON DESIGN AND CONSTRUCTION …...ASTM (2005). ³ Standard temperature for...
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AN ORAL PRESENTATION ON
DESIGN AND CONSTRUCTION OF A TUNNEL DRYER FOR FOOD CROPS
21st SAAFoST BIENNIAL INTERNATIONAL CONGRESS & EXHIBITION 6 – 9 September 2015, Southern Sun Elangeni /
Maharani Complex, Durban, South Africa
SEPTEMBER, 2015
BY
A.S. AJALA, P.O. NGODDY & J.O. OLAJIDE
Department of Food Science and Engineering Faculty of Engineering and Technology LADOKE AKINTOLA UNIVERSITY OF TECHNOLOGY, OGBOMOSO, NIGERIA
C:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docxC:/Users/Dr. A. S. AJALA/Desktop/S. AFR. FINAL/Ajala Invitation Letter-Copy.docx
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OUTLINE OF PRESENTATION
Introduction/Background of the Study
Statement of Research Problem
Research Aim and Objectives
Design methodology for the Dryer
Results and Discussion
Contribution to Knowledge
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3
Nigeria is the most populous nation in Africa with an
estimate of 160 million people
Background of the Study
Figure 1: Geographic Distribution of Nigeria
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Different Geographic areas in Nigeria is known for the
production of different crops
Background of the Study (contd)
Figure 2: Farming System in Nigeria
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Background of the Study (contd)
Table 1: Some farm produce in Nigeria
Product Metric tons (millions)
References
Cassava 37.5 +_ FAOSTAT, 2012
Maize 10 + Nigeria Bureau of Statistics, 2012
Yam 38 + Ibitoye and Onimisi (2013)
Tomatoes 1.7 + Donkoh et al., 2013
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Cassava
Background of the Study (contd)
Figure 3: Woman in Cassava Farm
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Maize
Background of the Study (contd)
Figure 4: Man in a Maize Farm
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Background of the Study (contd)
Figure 4: Woman selling pepper and tomatoes in Oshodi Market, Lagos
Pepper & Tomatoes
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Due to large expanse of fertile lands, many people are into farming and at the end of the year we can boast of excess supply of agricultural products more than we need or can consume.
Despite all these production almost 70% of these products are wasted
Statement of the Problem
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Statement of the Problem (Contd.)
Table 2: Wastages of farm produce
in Nigeria
Product Wastages (%) References
Cassava 13.3 P. E International, 2013
Maize 13.7 P. E International, 2013
Yam 10 FAO, 2013
Tomatoes 70 Umeofia, 2015
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Statement of the Problem (Contd.)
Some reasons for these wastages
includes:
Unavailability of storage facilities
Poor processing methods
Poor preservation methods
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Drying has been adopted by many farmers as a
means of preserving their farm products.
The types of drying available includes:
Sun Drying Natural Artificial
Mechanical dryers
Cabinet Infrared Vacuum Drum Tunnel
Statement of the Problem (Contd.)
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Natural sun drying Most adopted
It’s the cheapest
Its not effective as its weather dependent
Hence,
Mechanical dryers is considered to be a preferable and better alternative
Statement of the Problem (Contd.)
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This work introduces a general purpose tunnel dryer for food crop dehydration
AIM OF STUDY
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Design Features of the Constructed Tunnel Dryer
• It has both counter-current and co-current mode of drying
• Expected Production rate: 32.5kg/batch
• Expected number of trucks: 6
• Expected number of trays per truck: 6
• Air temperature before entering dryer: 32oC
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Description of major components and materials of construction
• Drying Chamber (Tunnel) • Heaters • Blower (fan) • Trucks • Trays • Return channel (pipe or duct) • Fasteners (bolts and nuts) • Lagging material (fiber glass) • Electrical/electronic components (wire, thermocouple,
and temperature regulator, humidity sensor and velocity regulator)
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Description of major components and materials of construction
• Drying Chamber (Tunnel) • Heaters • Blower (fan) • Trucks • Trays • Return channel (pipe or duct) • Fasteners (bolts and nuts) • Lagging material (fiber glass) • Electrical/electronic components (wire, thermocouple,
and temperature regulator, humidity sensor and velocity regulator)
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Front View of the Tunnel Dryer
Figure 5: Front view of the tunnel dryer
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Isometric view of the tunnel dryer
Figure 6: Isometric view of the developed dryer
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20 Figure 7: Isometric view of the developed Truck
Isometric View
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Truck design cont’d
Figure 8: Front view of the developed Truck
Front view
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Design of Trays • Length of tray=0.25m • Breadth of the tray= 0.20m • Height of the tray= 0.015m
• Design of Trucks • Height of the truck = 0.25m • Length of the truck = 0.30m • Breadth of the truck =0.2m
• Design for drying chamber of the tunnel
• Length of the drying chamber =3.25m
• Breadth of the drying chamber =0.35m
Design Specifications
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• Feed rate (mw) = 32.5 kg/hr
• Intended drying time = 6 hours
• Initial moisture content of the cassava chips = 75%
• Desired final moisture content = 14%
• Therefore, weight loss from wet to dried chips is calculated thus
where mw is the mass of wet cassava chips, m0 =initial moisture content (%) md is the mass of dried cassava chips, mf =final moisture content (%)
)
100
100( 0
f
wdm
mmm
)14100
75100(5.32
dm
Heater Design
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Quantity of heat required to remove the water = quantity of heat on the cassava • chips + latent heat of evaporation of • water inside the chips • Specific heat of cassava chips = 3.41kJ/kgoC (Hahn and Keyer, 1985)
• Latent heat = 4.186 x103 {(597- 0.56(Tpr)} (Youcef-Ali et al., 2001) • where Tpr is the product temperature
• Q = mass of cassava chips x specific heat of the chips x temperature difference + • Mass of water x 4.186 x103 {(597- 0.56(Tpr)} • = 32.5 x 3.41 x (80-30) + 23.05 x 4.186 {(597- 0.56 (60)} • = (5541.25 +57485.81) kJ • = 63025.06kJ • Power of heater to be used = Quantity of heat /Time • = 63025.06/ (6 x 3600) • = 2.905 kW • From the above calculation, a heater of about 3kW was used.
Heater Design
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• Length of the drying chamber (previously calculated) = 3.25 m
• Breadth of the drying chamber (previously calculated) = 0.35m
• Height at which chips fill each tray = 0.05m
• Total depth of chips for 36 trays = 36 x 0.05 =1.8m
• Volume of the material in the tunnel (m3) = 3.25 x 0.35 x 1.8 = 1.134m3
• Minimum required range of air velocity necessary for drying food products as recommended is 0.5 m/s (Bulent et al 2007; Ndukwu, 2009)
Fan Design
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Fan horse power (P) = volume air flow rates x total static pressure
6320 x fan efficiency
Most industrial fan have efficiency between 70- 85% (Adzimah and Seckley, 2009), Hence,
85.06320
638.101156.607
x
xP
= 2.29 Hp
A centrifugal fan with 2.5 Hp and 3.64 inches water pressure was used.
Fan Design
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Insulation Design
xg xs xa
T1 = 32oC
T2 =100oC
Aluminium
Sheet
Fibre Glass
Aluminium Sheet
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Thermal Efficiency
The thermal efficiency is given as
Tamb= ambient air temperature (30oC)
Tout= outlet air temperature (40oC)
Tin=inlet air temperature (70oC)
cov = 100T-T
T-T
in
outinx
amb
The thermal efficiency of the dryer was 75%
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29 Figure 9: Drying rate against time
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10
Drying time (hr)
Dry
ing
rate
(kg
/hr)
Drying Rate Pattern
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30 Figure 6: Truck distance against time
0
0.5
1
1.5
2
2.5
3
0 2 4 6 8 10
Tru
ck d
ista
nce co
vere
d (m
)
Drying time (hr)
Truck Movement Pattern in the Dryer
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31 Figure 10: Temperature against time
50
55
60
65
70
75
0 2 4 6 8 10
Tem
pera
ture
pro
file
(o
C)
Drying time (hr)
Temperature Pattern in the Dryer
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32 Figure 11: Air velocity against time
2
2.5
3
3.5
4
4.5
5
5.5
0 2 4 6 8 10
Air
velo
cit
y p
att
ern
(m
/s)
Drying time (hr)
Air Velocity Pattern in the Dryer
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• Processing relatively large volume of product
• Better control of drying parameters
• Cost effective drying and maximum product quality.
• Adaptable to drying tubers, fruits and vegetables
• Simplicity in construction
Advantages of using this tunnel dryer
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Samples of Products Dried
Picture of the constructed tunnel dryer
Samples of the dried cassava chips packaged in polythene film
Figure 12 : Dried Cassava Chips
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Samples of Products Dried
Figure 13 : Dried Egg
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Conclusions
• This dryer has catered for most deficiencies experiences with sun drying
• The maintenance cost is minimal because air (instead of gas) is used as drying agent
• The fans and heaters are capable to deliver the required heat needed for the drying operation
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Recommendations
• Further study on automation of the machine trucks will be a great advantage for drying of food products
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References
Adzimah K.S. and Seckley E. (2009). “Improvement on the design of a cabinet grain dryer”.
American Journal of Engineering and Applied Sciences 2 (1): 217-228.
Ajala, A.S., Ngoddy, P.O. and Olajide, J.O. (2013). Study of Drying Parameters in Tunnel
Drying. International Journal of Advanced Scientific and Technical Research, Issue 3 volume 2,
pp 265-266
ASTM (2005). “Standard temperature for measuring humidity with a psycrometer (the
measurement of wet & dry bulb temperature)”. Annual book of ASTM standards, section 11
volume 11.03 designation E337-02. American Society for Testing and Materials, International,
West Conshohocken, pp.1226-1249
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References contd
Hahn, S.K. and Keyer, J. (1985). “Cassava: A basic food for Africa”. Outlook Agriculture, 14
(9): 5-9.
Kiranoudis, C.T., Maroulis, Z.B. Tsami E. and Marinos-Kouris D. ( 1993) Equilibrium moisture
content and heat of desorption of some vegetables. Journal of Food Engineering, vol. 20, p. 55-
74.
Youcef-Ali, S., Messaoudi, H., Desmons, J. Y., Abene, A. and Le Ray, M. (2001).
“Determination of the average coefficient of internal moisture transfer during the drying of a thin
bed of potato slices”. Journal of Food Engineering, 48(2): 95-101.
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ACKNOWLEDGMENT
• The Management of Ladoke Akintola University of Technology, Ogbomoso, Nigeria
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Thanks for
Listening