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1
IV th International Conference on Advances in Energy ResearchIndian Institute of Technology Bombay, Mumbai
D.H. Kokate, D. M. Kale, V. S. Korpale, Y. H. Shinde, S.P. Deshmukh,S.V. Panse, A. B. Pandit*
Institute of Chemical Technology, Mumbai-19E-mail: [email protected]
Conservation of Energy through Solar Energy Assisted Dryer for Plastic Processing Industry
2
Contents
☼ Introduction☼ Construction of ISC based Solar dryer ☼ Development of mathematical model for solar
collector ☼ Drying kinetics of Nylon-6 and modeling of
drying process☼ Economic evaluation of solar dryer☼ Conclusion ☼ References
3
India’s Per Capita Consumption Is Just one fifth of the World Average !We need to Enhance our HDI by rapid mfg of Plastic Goods with sustainable Development.
4
1.1 Indian Plastic Industry
The Plastic Industry has growing 1.5 times of GDP ( 1995- 2005) with GDP @ 9% , the expected domestic demand of Polymer to Reach at 9.5 MMT. Increased Demand in Polymer will Increase the Energy Wastages ( If EC measures are not adopted/ neglected)
1995-96 2005-06 2011-120123456789
10
Year
Poly
mer
dem
end,
MM
T
9%
13%
5
The boosting Demand will reach to 12.8 MMT. The Growth Drivers are need to be closely monitored and policies need to integrated with EC Act 01 & RE Sources to promote the EC. Managing the Energy Demand to meet the Polymer demand @ 19 % is a challenge . Energy Management of using alternative energy sources will be a IMP tool to meet the above challenge.
1.1 Indian Plastic Industry
6
Energy
Distribution Blending
Rejects Process
Granulation Drying
Dispatch
Energy
Energy
Energy
Energy
0%
1%
2%
3%
4%
Use of energy for drying in various processes
1.2 Energy in plastic processing
•Total enthalpy of the drying process:
Where,HGG = Enthalpy of Humid gasHGW = Enthalpy of moistureHGM = Residual enthalpy for mixing
and other effectsY = Absolute humidity of gas
1.3 Low temp. Application in plastic processing for Solar Chimney / Dryer
Drying of hygroscopic Polymers & preheating of Polymeric materials up to 70 °C easily achieved by solar Chimney / Dryer
Common name Specific gravityMax. operating
temp. (°C) Solar Thermal ProcessAcrylic 1.18 55 Preheating up to 40°C
Acrylo Nitrile Butadiene Styrene (high impact)
1.04 70
LDPE 0.92 80PVC (flexible) 1.3 50PVC (rigid) 1.4 90 Preheating up to 50°C
Polycarbonate 1.15 115
Epoxies 1.2 130 Preheating up to 70°CPolyester 1.8 130PTFE 2.1 180
Silicones 1.4 240Nylon 6 1.14 220 De-humidification &
Preheating up to 70 °C
1.4 Scope for Solar Thermal in Plastic Processing
Solar Thermal Implementation measure Energy Reduction (expected)
Preconditioning of Polymeric Material. - Heating & Drying before processing. 7 – 10 %
Heating during Processing ( partially) 8- 12 % Effluent Treatment 5- 10 % Shop floor & Industry Lighting by Solar PV Panel
3- 5 %
Total 23 – 37 %
About 20 % cost reduction, in required energy is possible by using only Solar Thermal application that will reduce the cost of manufacturing / maximize the profit.
2.1 Concept of Solar Dryer
Temperatures of absorber plate
T1 T2
T3 T4
T5
T7
T9
T11
T13
T14
T6
T8
T10
T12
Temp. of drying tray
Temp. of drying MaterialTemperatures of air
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Different design:•Basic ISC design•Absorber lining inside the drying chamber•Some part Top cover was replaced by absorber cover from above
2.2 Solar Dryer Model
Drying material Properties:Good strength, stiffness, chemical and impact resistance, as well good frictional characteristics. Its diffusion characteristics show very different nature compared with other plastic materials.
Aperture factor,
Solar radiant energy falling on absorberConvection heat transfer coefficient between absorber plate and air
Convection heat transfer coefficient between
transparent cover and air Convection heat transfer coefficient of re-radiation from absorber plate to air through transparent cover Top loss coefficient Bottom loss coefficient
Mean temperature of absorber Mean temperature of cover Temperature of Ambient air Mean width of trapezoidal collectorLength of absorber plate
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3.1 Development of mathematical model for solar collector
𝐶𝑐=(1− 𝐴𝑒𝑛𝑐𝑙𝑜𝑠𝑢𝑟𝑒
𝐴𝑝)
Assumptions:
- bulk mean temperature of air rises from Tf to Tf +dTf
flowing through the distance dx
- The air mass flow rate md
- The mean temperature of absorber plate and cover are
Tpm and Tc respectively.
- Bottom and side losses are neglected.
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Energy balance for absorber plate:
Where
Energy balance for Cover:
Energy balance for air stream:
The final mathematical expression is,
0 1 2 3 4 5 6300
310
320
330
340
350
360
370
380Tfo(experimental)
Tfo(model)
Trials
Tfo
(K
)
Acceptable within 5 % variation
4.1 Temperature variation in natural Convection solar Chimney
10:00 11:00 12:00 13:00 14:00 15:00 16:0030
40
50
60
70
80
90
100
0
0.5
1
1.5
2
2.5
3Air temp & air velocity profile over the day
Air at in Air at 1 Air at 2 Air at 3 Air at out
outlet velocity inlet Velocity
Time, hr:min
Tem
p, o
C
Air
elo
city
, m/s
ec
∆T, achieved up to 40°C & air velocity up to 2 m/sec
10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 16:00 16:30280
290
300
310
320
330
340
350
360
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Pellet temperature and wind velocity
pellets temperature Wind velocity
Time, Hr:min
Tem
pera
ture
, K
Vel
ocity
, m/s
ec
4.2 Variation of pellet temperature and air velocity over a day
4.3 Thermal performance
Trial Tpm
(K)
md
(kg/s)Qi
(W)Qu
(W)ηth
%
E-11 339.4 0.117 6763 1630 24.1
E-21 340.8 0.132 9101 2215 24.3
E-31 336.3 0.115 5927 2043 35.7
Here is a scope to improve the Efficiency up to 40%
Trial Tpm
(K)
Tfo (exp.)
(K)
Pr Nu hfp
(W/m2 K)
hr
(W/m2 K)
E-11 339.4 331.5 0.72 5.95 1.66 5.67
E-21 340.8 331.8 0.72 5.38 1.47 5.71
E-31 336.3 328.6 0.72 5.30 1.73 5.62
16
10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 16:000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
E21 E31 E11
Time (Hr: min)
Dry
bas
is m
oist
ure
cont
ent (
%)
4.4 Drying Kinetics of Nylon-6 and modeling of Drying Process
17
4.4 Drying Kinetics of Nylon-6 and modeling of Drying Process
Effective moisture diffusivity was calculated for all the trials, and found to be in the range of 4 - 6.5 X 10-9
cm2/s. is in good agreement with the value reported in the literature which is 5 X 10-9cm2/s.
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
E21 E31 E11
Dry basis moisture content (%)
Dry
iing
rate
(g/g
. s)
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5.1 Dryer Sizing
Ms
(kg)Mw
(kg)Qe
(W)Qs
(W)Qd
(W)Qu
(W)Ap
(m2)
1 0.0162 10.73 1.99 12.72 33934 4.24
10 0.1628 107.3 19.93 176.75 33936 42.42
50 0.8140 536.6 99.66 176.75 11783 58.91
100 1.6281 298.1 199.33 353.50 23567 117.83
Assuming,1.5% drying efficiencyDry basis moisture content 9%Sample temp. 327KSolar Intensity 800W/m2
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5.2 Cost Analysis of solar dryer
The simple cost analysis approach is depicted for this topic and it shows the
total cost of any system is sum of cost of individual components. Solar dryer
consisting of collector and drying chamber.
The roof of the collectors may be withstanding maximum temperatures up to
80 0C, thus material should be quite stress resistant additional to
transparency. The collectors may be glass sheet, polycarbonate sheet or thin
polyster sheet.
Polyster sheet costs Rs. 72/m2 . Material cost for constructing the dryer is Rs.
50/m2 of collector area.
Total cost of dryer = collector cost + drying chamber cost + fabrication cost
= 72 + 50 + (72+50)
= Rs. 244 /m2 of collector area
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6. Conclusion
Drying behavior of Nylon-6 was investigated using natural convection solar drying.
Air temperature inside the dryer is found to be in the range of 55-70oC, which is
dependent on factors such as solar intensity, outside wind velocity, and type of
absorber etc.
Drying of Nylon-6 is found to be in the falling rate period. Nylon-6 took nearly 6 hrs
to reach 0.15 % moisture content value.
Value of effective diffusivity is varied from 4 - 6.5 X 10-9 cm2/sec. The results
presented in this work suggest that solar dryer can be satisfactorily used for drying
of Nylon-6.
Economic analysis show simple payback period for solar dryer capable of drying 100
kg/hr is around 7 months.
Solar Thermal Energy options can be quickly harnessed in plastic processing,
e.g. Pre-conditioning , Drying , and Preheating of Polymers.
21
References
1. CRISIL Infrastrure Advisory. Indian Plastic Industry-Vision 2012. Delhi, 2006.2. Indian Plastic Industry. 1999-2013. (accessed 2013).3. Canadian Industry Program for Energy Conservation,Natural Resources Canada.
Guide to energy efficiency opportunities in the canadian plastics processing industry. Ottawa ON K1A 0E4, 2007.
4. Tangram Technology. Energy efficiency in Plastic processing-Practical Worksheet for Industry. Tangram Technology Ltd.
5. D. M. Kale, R. G. Patil, A.B. Pandit, V. D. Deshpande, J. B. Joshi, S.V. Panse, “Economic Optimization of Inclined Solar Chimney for Power Generation “ISWESD, Assam,2012
6. A.S.Jadhav, A.S.Gudekar, S.V.Panse, J.B.Joshi. (2011). Inclined solar chimney for power production, Energy Conversion and Management 52, 3096–3102
7. S.P.Sukhatme, J.K.nayak. Solar Energy-Principle of Thermal energy collection and storage. Delhi: Tata McGraw Hill Publishing Company Ltd., 2008.
8. Y.H. Shinde Development of natural convective solar drying. Mumbai: Institute of Chemical Technology, 2009.
9. Nelson W.E. Nylon Plastic Technology. Newnws-Butterworths, London: Butterworth and Co.(Publishers) Ltd., 1976.
10. Psychometric Analysis C.D.-Psychart-1,American Society of Heating, Refrigeration and Air conditioning Engineering Inc., Copyright 1992
Thank you
Drying model