1. IV th International Conference on Advances in Energy Research
Indian Institute of Technology Bombay, Mumbai
Conservation of Energy through Solar Energy Assisted
Dryer for Plastic Processing Industry
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-19
E-mail: dr.pandit@gmail.com
1

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
2

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.
3

4. 1.1 Indian Plastic Industry
Polymer demend, MMT
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)
10
9
8
7
6
5
4
3
2
1
0
9%
1995-96
2005-06
Year
2011-12
4

5. 1.1 Indian Plastic Industry
 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.
5

6. 1.2 Energy in plastic processing
Energy
Energy
Blending
Distribution
Granulation
Drying
Energy
Rejects
Process
Energy
Dispatch
Energy
4%
3%
•Total enthalpy of the drying process:
2%
1%
0%
Use of energy for drying in various processes
Where,
HGG = Enthalpy of Humid gas
HGW = Enthalpy of moisture
HGM = Residual enthalpy for mixing
and other effects
Y
= Absolute humidity of gas
6

7. 1.3 Low temp. Application in plastic processing for Solar Chimney / Dryer
Max. operating
Common name Specific gravity
temp. (°C)
Acrylic
1.18
1.04
55
70
(high impact)
LDPE
PVC (flexible)
PVC (rigid)
Polycarbonate
0.92
1.3
1.4
1.15
80
50
90
115
Epoxies
Polyester
PTFE
Silicones
Nylon 6
1.2
1.8
2.1
1.4
1.14
130
130
180
240
220
Acrylo Nitrile
Butadiene Styrene
Solar Thermal Process
Preheating up to 40°C
Preheating up to 50°C
Preheating up to 70°C
De-humidification &
Preheating up to 70 °C
Drying of hygroscopic Polymers & preheating of Polymeric
materials up to 70 °C easily achieved by solar Chimney / Dryer

8. 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
Total
3- 5 %
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.

9. 2.1 Concept of Solar Dryer
Temperatures of air
T14
Temp. of drying Material
Temp. of drying
tray
T13
Temperatures of absorber plate
T11
T12
T9
T10
T7
T8
T5
T6
T3
T4
T1
T2

10. 2.2 Solar Dryer Model
Different design:
•Basic ISC design
•Absorber lining inside the
drying chamber
•Some part Top cover was
replaced by absorber cover
from above
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.
10

11. 3.1 Development of mathematical model for solar collector
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.
-
Aperture factor,
Bottom and side losses are neglected.
11

12. Energy balance for absorber plate:
Where
Energy balance for Cover:
Energy balance for air stream:
380
Tfo(experimental)
370
Acceptable within 5 %
variation
Tfo (K)
360
The final mathematical expression is,
Tfo(model)
350
340
330
320
0
1
2
3
Trials
4
5
6
12

13. 4.1 Temperature variation in natural Convection solar Chimney
Air temp & air velocity profile over the day
100
3
Air at 1
Air at 2
Air at out
outlet velocity
Air at 3
inlet Velocity
90
2.5
Temp, oC
80
2
70
1.5
60
1
50
40
0.5
30
10:00
0
11:00
12:00
13:00
14:00
Time, hr:min
15:00
16:00
∆T, achieved up to 40 C & air velocity up to 2 m/sec
Air elocity, m/sec
Air at in

14. 4.2 Variation of pellet temperature and air velocity over a day
Pellet temperature and wind velocity
350
pellets temperature
Wind velocity
7.0
345
6.0
340
Temperature, K
330
4.0
325
3.0
320
315
2.0
310
1.0
305
300
0.0
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 16:30
Time, Hr:min
Velocity, m/sec
5.0
335

15. 4.3 Thermal performance
Trial
Tpm
Tfo (exp.)
Pr
(K)
(K)
E-11
339.4
331.5
0.72
E-21
340.8
331.8
E-31
336.3
328.6
Nu
hfp
hr
(W/m2 K)
(W/m2 K)
5.95
1.66
5.67
0.72
5.38
1.47
5.71
0.72
5.30
1.73
5.62
md
(kg/s)
Qi
Qu
(W)
(W)
ηth
%
0.117
6763
1630
24.1
340.8
0.132
9101
2215
24.3
336.3
0.115
5927
2043
35.7
Trial
Tpm
E-11
(K)
339.4
E-21
E-31
Here is a scope to improve the Efficiency up to 40%

16. 4.4 Drying Kinetics of Nylon-6 and modeling of Drying Process
1.6
Dry basis moisture content (%)
1.4
1.2
E21
E31
E11
1
0.8
0.6
0.4
0.2
0
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
Time (Hr: min)
16

17. 4.4 Drying Kinetics of Nylon-6 and modeling of Drying Process
0.0003
E21
Dryiing rate (g/g . s)
0.00025
E31
E11
0.0002
0.00015
0.0001
0.00005
0
0
0.2
0.4
0.6
0.8
1
Dry basis moisture content (%)
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.
17

18. 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 efficiency
Dry basis moisture content 9%
Sample temp. 327K
Solar Intensity 800W/m2
18

19. 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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20. 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.
20

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
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22. Thank you

23. Drying model