Performance improvement of a passive solar still in a water desalination
Performance improvement of a passive solar still in a water desalination
F. M. Abed 0 1 2
M. S. Kassim 0 1 2
M. R. Rahi 0 1 2
0 Department of Mechanical Engineering, Tikrit University , Tikrit , Iraq
1 Editorial responsibility: Mohamed Fathy Yassin
2 Department of Mechanical Engineering, AL-Mustansiriyah University , Baghdad , Iraq
Using a solar energy in water desalination system is regarded as one of the most effective ways to resolve the problem of freshwater shortages in this world. Experimental and theoretical approaches were carried out to design and test multistage solar still. The experimental tests were conducted for five months in the city of Kirkuk, north of Iraq, at 43.39 longitudinal and 35.17 latitude. The performance requirement of the design is dependent on many factors such as circumstances, work and designation variables. Designating variables, mainly length, width, height and volume of each stage besides the number of all stages, are determined via theoretical analysis approach. The results obtained by both approaches have shown that there is a 10% deviation in still water productivity. Also, the results indicated that the minimum and maximum daily average of still water productivity is 1.7 and 3.8 kg. MATLAB software was employed to model and simulate the experimental processes of evaporation and condensation. The simulation model results were found to agree well with the experiments carried out in many other papers and studies. The test results reported that the system produces about 5 kg of clean water per day with 87% distillation efficiency and 26% of the overall efficiency due to heat losses in the system. Such system is not only promising, but can offer a new technology that can particularly be used in remote and rural areas. The theoretical calculations were compared with the experimental results, and there is a good agreement between the two .
Solar still; Multistage parabolic type; Distilled water; Solar collector
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Shortage of freshwaters is considered one of the most
serious environmental problems facing today’s world.
Most of the water available on earth is highly salty sea and
ocean waters, which is not suitable for drinking. Thus, the
world has no choice but to desalinate sea and ocean waters
efficiently at low cost. Solar distillation process appears to
be suitable to resolve this problem through purification of
salty water. Distillation process uses solar radiation, which
is a form of thermal energy produced by a multistage solar
still connected to a parabolic trough collector to improve
its performance and to increase production of distilled
drinking water.
Solar distillation uses simple device called solar
distillates in a process similar to the natural evaporation of water
by sun heat. Solar distillates are classified into two main
types: positive still and active solar still which adds a
number of external components such as concentrates or
solar collectors. Also, it includes two types with multiple
distillates that involving single and multiple basins. Basins
are of many types with oblique cover, two way cover, ring
cover and cone cover in addition to vertical distillates.
ALKaraghouli and ALnaser (2004) conducted an experimental
study on two stills, one with single basin and the other with
double basin. Both have the same internal basin area
(0.45 m2) with internal dimensions of 50 9 90 cm for each
still. The study was conducted based on two types of stills,
one a solar still with thermally insulated walls on both sides
and the other without insulated walls. A glass double basin
cover is tilted at 12 angle horizontally while the single
basin cover is tilted at 36 angle horizontally as well. Tests
were out on the two stills for the period from February to
June. Results showed that the highest average daily
production of distilled water is in June for both types due to
high solar radiation rate in June, and the average
production of distilled water by the isolated still is higher than
those obtained without isolation. Results also showed that
the daily production rate of water in the double basin still
was higher than single basin still by 40% with the same
operation conditions. Attaseth et al. (1985) have
manufactured two vertical identical stills to study the effect of
different lids made of glass and plastic on productivity rate.
Based on the same experimental operating conditions in
terms of operational system, design and weather conditions
thus showed that the productivity of distilled water with a
glass cover is higher than the using plastic cover by 10%.
Akash et al. (2000) studied the effect of using five different
angles of inclination a transparent cover (55 , 45 , 35 , 25 ,
15 ) on the solar distilled productivity. The study was
conducted in Jordan at different operating conditions.
Results have shown that 35 Æ angle inclination is the best
for the production of distilled water. Nijmeh et al. (2005)
conducted a theoretical and experimental study throu (...truncated)