1. International Journal of Mechanical Engineering (IJMET), ISSN 0976 – 6340(Print),
International Journal of Mechanical Engineering and Technology
and Technology (IJMET), ISSN 0976 – 6340(Print) © IAEME
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), IJMET
ISSN 0976 – 6359(Online) Volume 2
Number 1, Jan - Feb (2011), pp. 01-09 ©IAEME
© IAEME, http://www.iaeme.com/ijmet.html
EXPERIMENTAL INVESTIGATION ON COUPLING
EVACUATED HEAT PIPE COLLECTOR ON SINGLE
BASIN SINGLE SLOPE SOLAR STILL PRODUCTIVITY
Hitesh N Panchal
Assistant Professor
Mechanical Engineering Department
L C Institute of Technology, Mehsana Gujarat
Email: Engineerhitesh2000@gmail.com
Dr. Manish Doshi
Member of Institution of Engineer (MIE)
Anup Patel
Assistant Professor
L C Institute of Technology, Mehsana
Keyursinh Thakor
Assistant Professor
L C Institute of Technology, Mehsana
ABSTRACT
Solar still is very important device to convert the available brackish water into
drinkable water. Here work is carried out to know the effect of coupling an Evacuated
Heat Pipe Collector on the solar still. Other different parameters like Water depth, Sun
direction and solar radiation to enhance the productivity. It has found that coupling an
Evacuated Heat pipe collector with a solar still has increased the productivity by 32%.
Also it has found that the productivity is reduced while using higher water depth and
solar insolation is directly proportional to the Productivity.
Keywords: Pyranometer, Thermocouples, Evacuated Heat Pipe Collector
1. INTRODUCTION
O.O. Badran [1] performed experiment on single slope solar still using different
operational parameters like basin water depth, glass cover thickness, insulating materials
and proved that, productivity of distilled output is increased upto 51% when combined
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
enhancers such as asphalt basin liner and sprinkler have been applied on single slope
solar still. Kalidasa Murugavel et.al.[2] gave brief report on solar desalination regarding
with various methods of improving the productivity. They suggested that different
materials are used in basin solar still to improve the heat capacity, radiation absorption
capacity and condensation rate. Kalidasa Murugavel at.al [3] used different wick
materials like light cotton cloth, light jute cloth, sponge sheet of 2 mm thickness and
different porous materials like washed natural rocks of different average sizes. He proved
that wick materials could improve the distilled output. M.E. El-Swifty and M.Z.
Metias[4], said some sun rays are received by the back plate and side plates of the basin,
hence this effect reduces the amount of radiation available to the basin for heating. So
they used reflecting mirrors. After, Imad Al-Hayek and O O Badran [5]proved that single
slope solar still with reflecting mirror increase the distilled output 20% more than double
slope solar still. H.A. Tahaineh and O.O. Badran [6] used solar collector coupled with
solar still and investigated that the productivity. They took different parameters like water
depth, direction of solar still, solar radiation to enhance the solar still productivity. They
found that coupling of flat plate collector with solar still can increase the productivity
upto 20%.Hazim Mohammed Qibdawey.et.al [7] has presented paper entitled “solar
thermal desalination technologies”. He has shown the direct and indirect desalination
technologies of solar still like vapour compression, multistage flash evaporation,
membrane distillation etc. They said Evacuated glass tube collector is more useful
compared with flat plate collector. They also suggested that, coupling a CPC can increase
the temperature more than Evacuated glass tube collector and Flat Plate collector. Rajesh
Tripathi. et.al[8] as found the distribution of solar radiation using concept of solar
fraction inside the single slope solar still by using Auto Cad 2006 for given azimuth angle
and latitude angle. From numerical computations, climate conditions of New Delhi have
been carried out.M Bouker.et.al [9] has done performance of simple solar still compared
with coupled one. He tasted for all day productivity under clear sky conditions with
different depth levels of brackish water for winter and summer period from Jan to March.
2000. He found that productivity in summer period varied from 4.01 to 4.34 L/m2/Day
for simple basin and 8.02 to 8.07 L/m2/Day for coupled so Tiwari.et.al [10] have done
thermal analysis of double effect distillation unit in active operation. He observed that
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3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
increase of 30% and 20% in efficiency of solar distillation working under active and
passive mode.H.N. Singh.et.al [11] have done experiment on active and passive solar still
for different climate conditions like Chennai, Jodhpur, Kolkata and Mumbai on the basis
of numerical computation. He has found that annual yield significantly depends on water
depth, condensing cover inclination for both active and passive solar still and annual
yield for a given water depth increasing linearly with collector area for active solar
still.Rustam Mamlook.et.al [12] have taken a case study of solar distillation system by
fuzzy sets. The study reveals that wind speed, ambient temp, solar intensity, sprinkler,
coupled collector, solar concentration, water depth etc. Based on increase of production
results show that factors were found to affect on yield of solar still. Tiwari et al.[13] have
been developed a computer model to predict the performance of single slope solar still
basin on both inner and outer glass temperature. They concluded that there is a significant
effect of operating temperature range on the internal hears transfer coefficients.
Voropoluos et.al. [14] Evaluated experimentally and theoretically a simple and efficient
method for the behaviour of solar stills. Their method relates the main climate data and
operating conditions of the still with distilled water output in daily and night base with
linear equations using characteristics coefficient. Kumar.et.al [15] presented the annual
performance of an active solar still. Analytical expression for water and glass cover
temperature and yield has been derived in terms of design and climate parameters.
Numerical computations have been carried out for Delhi climate conditions. it has been
observed that for given parameters, annual yield is optimum when the collector
inclination is 200 and the still glass cover inclination is 100.Rajesh Tripathi.et.al [16] has
used semi cylindrical condensing cover and he has used temperatures of 40 to 80C and
found that there is an increase of about 15% in the evaporative heat transfer coefficient
due to the size of the condensing cover and increase of about 7.5% of evaporative heat
transfer coefficient due to change of material. Malik & Sodha.[17] attached a hot water
storage tank to the solar still and they proved that coupling of hot water storage tank
increase the 10% distilled output of single slope solar still.
Our goal for the present investigation on solar still is to design and develop an
improved solar still which can use in house of India as well as output of a solar still
through Evacuated Heat Pipe Collector under Indian Climate Conditions.
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4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
2. EXPERIMENTAL SET UP
Figure 1 Schematic Diagram of Solar still coupled with Evacuated Heat pipe Collector
Present investigation consists of solar still coupled with Evacuated Heat Pipe
Collector. It has black painted basin of area of 1 square meter filled with brackish water
supplied to it from a collector which preheats the water by use of solar energy, such kind
of solar still also called Active Solar still. The evaporating basin is covered by a sheet of
toughened glass having 4 mm thickness which allows the sunrays directed to basin.
Angle of tilting the glass cover is 15 degree. A trough running along the bottom side of
the glass cover ensures the collection of the potable water toward the collecting vessel.
The glass also holds the heat inside the still for continuing the evaporation of
water inside the basin. An inlet pipe is fixed at the rear of the still for feeding the brackish
water. Holes were drilled in the body of still to fix the thermocouples (to measure the
various temperatures of solar still). An Evacuated Heat Pipe Collector (1.50 m long, 0.5
m width and 0.20 m thick) has been used to evaporate the water which is inside the basin.
The Evacuated Heat Pipe Collector is made of many parallel tubes having ½ inch
diameter and 1.6 m length.
In this Solar still following factors have highly considered for the investigation:
• To made simple in construction, maintenance and operation.
• To be rigid and firm enough to resist the worst environmental Conditions.
• Local materials have used for making low cost solar still. Figure 2 Shows
Evacuated Heat Pipe Collector.
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5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
Schematic Diagram of the system is shown in figure 1A rectangular trough is
fixed at the downstream end of the slope for collection of the potable water. The solar
still is filled each morning and days production is collected at the time interval of 1 Hour.
Silicon rubber is used as sealant to prevent the heat losses inside the solar still as well as
leakage losses. The side walls and base of the solar still are insulated with locally
available material called “Rock Wool” having thermal conductivity of 0.034 W/m2 K of 5
cm thick. A constant Head tank was used to control the brackish water inside the solar
still. Depth of water level was maintained 2 cm during the period of investigation work.
The solar still has been designed installed and operated at Ahmedabad.
Figure 2 Evacuated Heat pipe Collector
3. RESULT & DISCUSSION
In this Research paper I report on daily experimentation of a single slope solar
still and same still coupled with evacuated Heat pipe collector. The system was operated
continuously for several months of year 2010 (April to October) under different climate
conditions with good and low sunshine. The work aimed to enhance the solar still output
through improving the still operations condition by using Evacuated Heat pipe Collector.
The temperatures of brackish water, glass cover (Inner glass cover and outer glass cover),
vapor temperature and ambient temperature were recorded continuously.
This solar still unit mounted on angled iron stand which is movable to make any
adjustment to the angle of axis of still to enhance enhanced solar radiation for better
output. The standard orientation of the solar still was assumed to be towards south to
receive maximum solar insolation.
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6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
The influence of climate conditions and mainly the solar insolation on the solar
still production is investigated without coupling an evacuated heat pipe collector i.e. solar
still alone. The variations of daily solar still output and average solar radiations for
different days in September are shown in figure 3
4000
3500
Daily yield in ml
3000
2500
Series1
2000
Series2
1500
1000
500
0
25
52
59
62
65
3
4
6
0.
0.
0.
0.
0.
0.
0.
0.
Average Solar radiations
(Kw./Square meter)
Figure 3 Relation of the solar insolation and solar still output during September, 2010.
Figure 3 shows that solar still productivity is proportional to the solar insolation
or radiation (Direct radiation + Diffused radiation), which depends on climate conditions
of each day. The effect of coupling a solar still with evacuated heat pipe collector is
shown in figure 4. From figure 4, it can be concluded that,
800
700
600 Solar still coupled
Yield in ml
500 with evacuated Heat
pipe collector
400
Alone solar still
300
200
100
0
0
0
0
0
0
0
:0
:0
:0
:0
:0
:0
10
11
12
13
14
15
Time (Hr.)
Figure 4 Comparison of yield between alone solar still and coupled solar still
There is proportionality in fresh water production (yield) with respect to the basin
water temperature. The higher the temperature of water, higher output will be from the
solar still as fresh water or distilled water. This productivity is expected as a result of
coupling an evacuated heat pipe collector with solar still because of supply of artificial
heat source with solar radiation. Coupling an evacuated heat pipe collector with solar still
has higher efficiency compared with alone solar still, because increase in temperature of
water inside the basin, increase the rate of evaporation and condensation so higher
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7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
distilled water. Comparison between efficiency of alone solar still and solar still coupled
with evacuated heat pipe collector is shown in figure 5
70
60
alone solar still
Efficiency (% )
50
40
30 solar still coupled
with evacuated heat
20 pipe collector
10
0
0
0
0
0
0
0
:0
:0
:0
:0
:0
:0
10
11
12
13
14
15
Time (Hr)
Figure 5 Comparison of efficiency between alone solar still and coupled solar still
The percentage of improvement in daily productivity due to coupling an
evacuated heat pipe collector (3029 mL)) is calculated and found to be 30% more than
that when the solar still was operated alone (2300 mL) Figure 6 Shows the results of
experiments performed during month of September to determine the optimum angle for
the solar still by changing the solar sill direction few degrees towards the east and west
from the geographic south to detect the optimum angle that will give the best yield. Such
deviation is required as the movement of the sun varies in direction between summer and
winter. From the productivity of the solar still, it can be seen that the optimal angle is
found to be 15 degree to the west of the geographic south during the winter season in
Ahmedabad. These results show that, tracking the sun is one of the best methods to
increase the yield from the solar still.
3500
3000
2500
Y i e l d (m L )
2000
Series1
1500
1000
500
0
0 10.W 10.E 15.E 15.W 20.E 15.W
Direction (In degree)
Figure 6 Effect of solar still direction on yield.
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8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
Time versus water depth
1200
Distillted Output (m m )
1000
800 1.5 cm water depth
600 2.5 cm water depth
400 4 cm water depth
200
0
0
0
0
0
0
0
:0
:0
:0
:0
:0
:0
10
11
12
13
14
15
Time ( Hr)
Figure 7 Effect of various depths on solar still
Figure 7 shows the productivity of the solar still as a function of basin water
depth, it is known that the productivity decreases with the increase of the water depth.
This increase in still productivity as a depth decrease could be attributed to the lower heat
capacity. (Lower heat capacity, higher the yield from the solar still).It can be concluded
that the output of the solar still is maximum for the least water depth in the basin. Figure
7 shows the comparison between various water depths.
4. CONCLUSION
The operation of a solar still coupled with evacuated Heat pipe collector has been
investigated experimentally. Comparison of the productivity between coupled solar still
and alone solar still was studied. It has found that productivity of coupled solar still was
found to be 30% higher than alone solar still. It also shown that present solar still design
leads to higher distillate water output (yield) due to higher temperature of basin.
REFERENCES
[1] O.o.Badran. Experimental study of enhancement parameters on a single slope solar
still productivity, Desalination, 209(2007) 136-143.
[2]K.Kalidasa Murugavel, Kn.K.S.K. Chockalingam, Srithar K. Progress in improving
the effectiveness of the single basin passive solar still, Desalination 220 (2008) 677-
686.
[3]K.Kalidasa Murugavel, Kn.K.S.K. Chockalingam, Srithar K. An experimental study of
single basin double slope simulation solar still with thin layer of water in the basin,
Desalination 220 (2008) 687-693.
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9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online) Volume 2, Number 1, Jan - Feb (2011), © IAEME
[4]O.O. Badran, Al-Tahaineh A. H. The effect of coupling a flat plate collector on the
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