PRATIBHA: INTERNATIONAL JOURNAL OF SCIENCE, SPIRITUALITY,
BUSINESS AND TECHNOLOGY (IJSSBT), Vol. 4, No. 2, May 2016
ISSN (Print) 2277—7261
Mathematical Analysis of Solar Water Distillation System
Using Copper Basin
Aniruddha Y. Chaudhari
Email:[email protected]
Dr. Atul A. Patil
Asst. Prof. GF‘s, Godavari College of engineering, Jalgaon
Prof. V. H. Patil
H.O.D. Mech. GF‘s, Godavari College of engineering, Jalgaon
Abstract: Clean water is the essential for good
health and the development of country. Most of
water available on the earth is salty i.e. sea
water. Hence we need to desalinate the water.
Solar still is the simple and low cost method to
purify the water. It uses solar energy as input to
get pure water from the brackish water as
output. In this paper solar still made of copper,
basin is studied theoretically. An attempt is
made to analyze the performance of solar still
with the help of equations to predict the output
of solar still.
1. INTRODUCTION
Water with good quality is the basic need
of human being. One can not imagine life without
water. We have only few resources of water like
river and lakes. Most of the water available for
drinking is underground water. The underground
water is generally hard due to dissolved salts. And
hence it cannot be directly used for drinking. So
we need to remove the salts from the water. There
are various methods to purify the water like
Electro Dialysis, Reverse Osmosis etc. [7] The
simplest method used to purify the water is solar
water distillation system or simply solar still. It is
the thermal method for desalinating the water. The
solar still may be single slope or double slope as
shown in fig.1 and fig.2 respectively. Here the
study is carried out for single slop single basin
solar still,[9]
Keywords: - Mathematical analysis, solar still,
Copper basin
Fig.1- Single slop solar still
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PRATIBHA: INTERNATIONAL JOURNAL OF SCIENCE, SPIRITUALITY,
BUSINESS AND TECHNOLOGY (IJSSBT), Vol. 4, No. 2, May 2016
ISSN (Print) 2277—7261
Fig.2- Double slop solar still
The increase in the use of energy and
environment effects has focused the attention on
non conventional energy sources. Solar energy is
available on earth at free of cost. Solar energy can
be used as thermal energy. It is also non polluting
and easily available. It also reduces the
transportation cost of fuel. the simple solar still can
produce the pure water required for drinking and
cooking for a house. Also those distilled water can
be used in many industrial processes. It is the
simple technology that uses solar energy to drive
the system. Ia has almost zero maintenance cost
and can be operated by non-skilled worker.
The problem associated with the
conventional solar still is that it has low
productivity. Various experiments are carried out
to improver the efficiency of solar still such as the
inner surface if the basin is painted with black
coating [5], use of reflecting material on the inner
side of solar still [7], application af vacuum inside
the solar still [4].
From the above experiments the output
of the solar still is improved.
4.
5.
6.
The solar radiations are not absorbed by
the vapors between the water level and
glass.
Water in the basin is at uniform
temperature.
The reflection of solar radiations is
neglected.
2.1 Energy balance for water in the basin[2]
I1+Qb+ (mwxCp) x dTw/ dt = Qcw+ Qew+ Qrw+I2 -------(1)
I1 = (1-ɑg)
I2 = (1-ɑg) (1-ɑw) I
Where ɑg and ɑw are the radiation absorptivity of
glass and water respectively.
2.2 Energy balance for glass:-
𝑄𝑟𝑔 + 𝑄𝑐𝑔 + 𝐼1 = 𝑄𝑐𝑤 + 𝑄𝑒𝑤 + 𝑄𝑟𝑤 +
𝐼 ----- (2)
2.3 Energy balance for basin:-
2. Theoretical Analysis:-
𝐼2 = 𝑄𝑏 + 𝑄𝑏𝑜𝑡 ----------------- (3)
The operation of solar still at any time is
determined with the help of energy balance. Fig.3
shows the energy transfer inside and outside the
solar still which is related to the output of the solar
still
The Various heat transfers can be calculated
by following equations
The radiative heat transfer between
water and glass (𝑄𝑟𝑤 ) is [2]
𝑄𝑟𝑤 = 𝑕𝑟𝑤 𝐴𝑤 𝑇𝑤 − 𝑇𝑔
Where,
hrw= Ɛeff ζ [(Tw+273)2+(Tg+273)2](Tw+
Tg+546)
Where,
σ = 5.669 × 10 -8W/m 2K 4
Ɛeff =
1
Ɛ𝑔
1
−1
+Ɛ −1
𝑤
Ɛ𝑔 = Ɛ𝑤 = 0.9
Fig.3- Energy transfer in single slope solar still
The convective heat transfer between
water and glass (𝑄𝑐𝑤 ) is [2]
The theoretical analysis is done with the following
assumptions [1],[2],[3]
1. There is not any vapour leakage.
2. The heat capacity of glass, basin material,
and insulation is neglected
3. The physical properties do not change
with temperature.
𝑄𝑐𝑤 = 𝑕𝑐𝑤 𝐴𝑤 𝑇𝑤 − 𝑇𝑔
hcw=0.884 𝑇𝑤 − 𝑇𝑔 +
𝑃𝑤−𝑃𝑔𝑇𝑤+273268.9𝑋103−𝑃𝑤13
28
PRATIBHA: INTERNATIONAL JOURNAL OF SCIENCE, SPIRITUALITY,
BUSINESS AND TECHNOLOGY (IJSSBT), Vol. 4, No. 2, May 2016
ISSN (Print) 2277—7261
where,
Pw=
Hourly yield of solar still is given by.
𝑞 𝑒𝑤 𝐴 𝑤
mw=
𝑥3600
5144
𝑇𝑤 +273
25.317 −
𝑒𝑥𝑝⁡
𝐿
Where,
mw- mass of water evaporated(kg)
qew- evaporative heat transfer from water to glass
(W/ m2)
Aw- area of water(m2)
L- Latent heat of evaporation
5144
Pg=
25.317 −
𝑇𝑔+273
𝑒𝑥𝑝⁡
Where
Pw-partial vapor pressure at water temperature
Pg- partial vapor pressure at glass temperature
Tw – Water temperature
Tg – Glass Temperature
The Evaporative heat transfer between water
and glass (𝑄𝑒𝑤 ) is [2]
Using above formulae the theoretical output of the
solar still can be calculated.
3. Solar still Specification
The specifications used for theoretical
analysis are given in table.1
𝑄𝑒𝑤 = 𝑕𝑒𝑤 𝐴𝑤 𝑇𝑤 − 𝑇𝑔
hew =16.27𝑋10−3 𝑋𝑕𝑐𝑤𝑋
𝑃𝑤 −𝑃𝑔
𝑇𝑤 −𝑇𝑔
Table.1- Specifications for solar still
The convective heat transfer coefficient between
glass and surrounding is given by,[1]
Specification
Basin Area ,m2
Glass Area ,m2
Glass Thickness, m
Number of glass
Slope of glass
Absorptivity of glass,𝛼 g
Absorptivity of Water,𝛼 w
Absorptivity of basin,𝛼 b
(Cu)
Emissivity of Glass,Ɛg
Emissivity of Water,Ɛw
𝑕𝑐𝑔 = 2.8 + 3𝑉
𝑄𝑐𝑔 = 𝑕𝑐𝑔 𝐴𝑔 𝑇𝑔 − 𝑇𝑎
Where,
V- Wind velocity
The radiative heat transfer coefficient between
glass and surrounding is given by,[3]
𝑇𝑔
4
– Tsky4 )/ (Tg – Ta )
𝑕𝑟𝑔 = 𝜀𝜍
𝑄𝑟𝑔 = 𝑕𝑟𝑔 𝐴𝑔 𝑇𝑔 − 𝑇𝑠𝑘𝑦
Dimension
1
1
5x10-3
1
20°
0.0475
0.05
0.25
0.9
0.9
RESULTS : To calculate the theoretical output of solar still the data is taken from various papers to solve
the different equations.
Table.2-Solar still with copper basin
Time(hr)
Solar
intensity
(W/m2)
Basin
Temperature
(°C)
Water
Temperature
(°C)
Glass
Temperature
(°C)
Hourly
Output
(ml/m2)
9
290
32.8
30.8
21
0.1
10
425
45
32.1
23.6
0.248
11
635
50.5
40.6
27.9
0.3
12
785
58.9
50.2
31.2
0.311
13
740
55.7
55.3
27.9
0.302
14
680
53.9
59.87
27.2
0.298
15
598
48.7
46.4
25.3
0.287
29
PRATIBHA: INTERNATIONAL JOURNAL OF SCIENCE, SPIRITUALITY,
BUSINESS AND TECHNOLOGY (IJSSBT), Vol. 4, No. 2, May 2016
ISSN (Print) 2277—7261
1.
16
445
41.9
38.3
22.7
0.276
17
335
34.2
31.6
21.6
0.265
18
210
28.6
28.4
20.4
0.245
Variation in temperature due to solar
radiation
The variation in basin, water and glass
temperature according to solar radiation are
shown in fig.
CONCLUSION
A mathematical model is used to predict the
performance of solar still made up of copper basin
with different parameters. It is found that the
efficiency of the still increases with the increase in
solar intensity.
80
Basin
Tempera
ture (°C)
60
40
REFERENCES
D.W.Medugu and L.G.Ndatuwong,‖ Theoretical Analysis
of water distillation using solar still‖, International Journal
of Physical Sciences,Vol.4,pp 705-712,2009.
[2] Omar Badran, ―Theoretical Analysis of solar distillation
using Active solar still‖, IJTEE,Vol.3,No.2,pp 113120,2011.
[3] Dinesh Kumar and Prashant Kumar, ― Mathematical
Modelling of Conventional Solar Still Coupled With Solar
Air Heater‖, IJISET,Vol-1, Issue 9,pp 379-383,2014
[4] Moses KoilrajGnanadason, PalanisamySenthil Kumar,
GopalSivaraman, Joseph Ebenezer Samuel Daniel,‖
Design and Performance Analysis of a Modified Vacuum
Single Basin Solar Still‖, Smart Grid and Renewable
Energy, 2011, 2, 388-395, doi:10.4236/sgre.2011.24044
[5] S. Nanda kumar, P.P.Shantharaman‖ Fabrication of solar
water distillation system‖, International Journal Of Core
Engineering & Management (IJCEM), Volume 2, Issue 1,
April 2015,pp 179-186.
[6] Hitesh N Panchal and P. K. Shah,‖ Performance Analysis
of Solar Still Having Different Plates‖, International
Journal of Energy Science IJES Vol.2 No.1 2012 PP.2629
[7] A.Balavignesh, D.B.Sivakumar,‖ Investigation On The
Single Slope Solar Still With Reflecting Materials‖,
International
Conference
on
Energy
Efficient
Technologies For Automobiles (EETA‘ 15),
JCHPS
Special Issue 6: March 2015,pp 170-172.
[8] RegilBadusha and T V Arjunan,‖ Performance Analysis
Of Single Slope Solar Still‖, IJMERR, Vol. 2, No. 4,
October 2013,pp 74-81
[9] Juan CristóbalTorchia-Núñez, Jaime Cervantes-deGortari,Miguel Angel Porta-Gándara,‖ Thermodynamics
of a Shallow Solar Still‖, Energy and Power Engineering,
2014, 6, 246-265
[10] Amos Madhlopa,‖ Development of an advanced passive
solar still with separate condenser‖, 2009.
[11] Sathish Kumar T R, Raja Bharathi B,‖ Effect of Water
Depth on Productivity of Solar Still with Thermal Energy
Storage‖, International Journal of Science and Research
(IJSR), Volume 2 Issue 3, March 2013,pp 413-417
[1]
Water
Tempera
ture (°C)
20
0
9 11 13 15 17
Fig.4 Temperature variation for solar still made up
of copper.
From the graph it is clear that with
the increase in solar intensity the temperature
of basin, water and glass increase up to noon
and with the decrease in solar intensity the
temperature of basin, water and glass
decreases during evening.
1000
800
600
400
200
0
Solar intensity (W/m2)
9
10
11
12
13
9 10 11 12 13 14 15 16 17 18
Fig.5 Variation of solar intensity with time
0.4
Hourly Output (ml/m2)
9
0.3
10
0.2
11
0.1
12
0
13
9
11 13 15 17
14
Fig.6 Hourly output of the solar still with time
30