Performance Study of a Solar Still using ANSYS

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 04, 2016 | ISSN (online): 2321-0613

Performance Study of a Solar Still using ANSYS 1,2

Arya J1 Sreenath B2 Amal Jyothi College of Engineering Kanjirapally

Abstract— Solar distillation system proves to be a promising technique for water purification. The function of solar still is to produce fresh water based on evaporation process, utilizing the solar energy. The performance of the solar still is compared with different temperature for feed water by considering with and without preheating of water using ANSYS. The instantaneous efficiency of the still is also determined by using ANSYS. Key words: ANSYS, Efficiency, Solar still, Solar energy I. INTRODUCTION Water is the foundation of life. Water touches every aspect of our lives from drinking and showering, to growing food and livestock, to generating electricity. Only less than 1% of the world’s fresh water (or about 0.007% of all water on earth) readily accessible for direct human use[1].On one hand demand for fresh water is on the rise and on the other hand pollution of water sources is increasing at an alarming rate. The pollution of water resources is increasing drastically due to a number of factors including growth in the population, industrialization, urbanization, changes in the life style of people etc. These activities adversely affect the quality of drinking water. In developing countries, lack of safe and unreliable drinking water constitutes a major problem. Unfortunately underground water is not always considered to be fresh drinking water, instead it is called brackish water. The salinity of brackish water varies with locations.

Thermal desalination, often called distillation, is one of the most ancient ways of treating seawater and brackish water to convert them into potable water. It is based on the principles of boiling or evaporation and condensation. Water is heated until it reaches the evaporation state. The impurities are left behind while the vapor is condensed to produce fresh water .Solar energy, which is abundantly available in the water scarce areas, can be used as a source to run the desalination process. One of the oldest and simplest solar based desalination apparatus is the solar still and it can serve as a small scale domestic water supply. A solar still operates similar to the natural hydrology cycle of evaporation and condensation. The basin of the solar still is filled with impure water and the sun rays are passed through the glass cover to heat the water in the basin and the water gets evaporated. As the water inside the solar still evaporates, it leaves all contaminates and microbes in the basin. The purified water vapor condenses on the inner side of the glass, runs through the lower side of the still and then gets collected in a closed container. The use of solar energy is more economical than the use of fossil fuel for distillation in remote areas having low population densities, low rain fall and abundant available solar energy.

Solar energy is available in abundant in most of the rural areas and hence solar distillation is the best solution for rural areas and has many advantages of using freely available solar energy. It is a simple technology and more economical than the other available methods. Many solar

distillation systems were developed over the years using the above principle for water purification.

II. SOLAR STILL REVIEW Desalination of seawater has become one of the most important commercial processes to provide fresh water for many communities. The numerous parameters are affecting the performance of the still such as water depth in the basin, material of the basin, wind velocity, solar radiation, ambient temperature and inclination angle. It was found that the solar radiation is the most affecting parameter on the productivity.

The productivity decreases with the increase of the wind speed due to the decrease in the fractional energy of evaporation. Furthermore, when the brine depth was increased the productivity decreased. Moreover, it was found that in summer the tilt angle of the glass cover should be maintained as small as possible because the horizontal plane receive more radiation than the inclined plane does, while in winter the productivity increases when the inclination is increased.[5]. In most of the previous literature the tilt angle of the condensing surface is made close to the latitude of the place.

The main factor for condensation process in solar still is difference between glass temperature and water temperature. As their difference is more is the speed of condensation. The effect of glass cover thickness has an effect on productivity. It is suggested that 4 mm thickness is optimum for enhanced water production. Solar still having glass cover thickness 4 mm produces more distillate output than 8 mm, 12 mm. Lower glass cover thickness decrease inner glass cover temperature inside solar still and increases temperature difference between water as well as inner glass cover temperature.

III. PROPOSED SYSTEM Various factors that affect the productivity of a solar still is discussed earlier. Temperature of feed water can be considered as one of the major factor that can be affect the productivity of the still. As the temperature of the feed water increases the evaporation time for the water will reduce and the productivity will increase. This paper is a simulation study of the productivity of a still by varying the temperature of using ANSYS. The Computational Fluid Dynamics (CFD) tool has been used to simulate the different water temperature condition. It explains how the efficiency of the still varies when the temperature of feed water varies.

Certain assumptions for the still is considered while simulation is done. The assumptions were given in the table Part of the still Assumptions made Still outer Counter wood box(180cm*83cm) Still basin Galvanized iron sheet Side walls Aluminium Glass cover(4.5mm Top cover thickness) Table 1: Assumptions Taken

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Performance Study of a Solar Still using ANSYS (IJSRD/Vol. 4/Issue 04/2016/334)

The tilt angle of the top glass varies with the latitude and longitude of different location. The value of optimum tilt angle at a particular location can be obtained by using a software named PV Syst. The tilt angle for the particular simulation is by setting Kanjirapally as the experiment location (9.5573◦N, 76.7894◦E). The optimum value of tilt angle obtained by using this software is 12◦.

The PV Syst simulation for optimum tilt angle is shown in Fig.1.

Fig. 3: Temperature contour of a double slope still for 85◦C Mass flow rates for different temperature is obtained by simulation. From that obtained mass flow rate the efficiency of the still is being calculated and a graph is plotted with efficiency and time of the day and is shown in Fig. 4. From.

Fig. 1: Optimum tilt obtained using PV System From the simulation result obtained the efficiency of the still can be determined by using the equation η = Qe/Qt (1) Qe = m ∗ Hv (2) Hv = Latent heat of vaporization m = Mass of water evaporated Qt = Total solar energy incident on solar still Qt = 4800 watt/hr sqm for 8 hours during summer Qt = 1800 watt/hr sqm for 6 hours during winter The value of Qt is obtained with the help of latitudes and longitude of the particular location.

IV. RESULTS AND OBSERVATIONS Two different feed water temperature is studied using ANSYS. The temperature contour for different feed water temperature is shown in fig. 2 and 3. The temperature contour almost remains the same. Only the temperature of feed water varies. The maximum temperature will be at the basin of the still because it is coated with a black paint and heat will be absorbed at the base part. The glass cover will be at optimum temperature because condensation occurs at the glass cover.

Fig. 4: Efficiency The efficiency graph plotted it is noticed that the efficiency of the still has improved when the temperature of feed water increases. This may reduce the evaporation time for the water and more water will be evaporated and condensed on the glass cover. There are several methods that can be employed to increase the temperature of feed water. They can be by using flat plate collectors, evacuated tube collectors and solar ponds etc.

V. CONCLUSION From the simulation results it can be analysed that by increasing the temperature of the feed water the productivity of the solar still also increases. So it can be concluded that a solar still integrated with a flat plate collector or an evacuated tube collector can improve the productivity of the still and by implementing such system pure water can be obtained easily. The major advantages of such type of stills are that it doesn’t cause any pollution and these these system will not destroy any habitat. It doesn’t consume any electricity.

REFERENCES

Fig. 2: Temperature contour of a double slope still for 32◦C

[1] http://www.acquainnovations.com/water-facts/ accessed on 12 April 2015 [2] Hassan E.S. Fath. High performance of a simple design, two effect solar distillation unit. Desalination 107: 223-233, 1996

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Performance Study of a Solar Still using ANSYS (IJSRD/Vol. 4/Issue 04/2016/334)

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