C. Nithyanandam et al., International Journal of Advanced Engineering Technology E-ISSN

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1 Research Paper DESIGN AND FABRICATION OF PASSIVE SOLAR DESALINATION SYSTEM WITH CALCIUM CHLORIDE HEXA HYDRATE AND LAURIC ACID C. Nithyanandam 1 G. Baskar 2 R. Umamaheswari 3 Address for Correspondence 1 Phd Scholar, Anna University, Chennai , Tamilnadu, India 2 Principal, Bharathidasan Engineering College, Vellore , Tamilnadu, India. 3 Associate Professor, Velammal Engineering College, Chennai , Tamilnadu, India. ABSTRACT The paper presents the effect of Calcium chloride hexa hydrate and lauric acid on heat transfer coefficient for a passive single-slope distillation system in summer climatic condition. The experiments have been conducted on a south facing, single slope, solar still of 10 inclination of condensing cover, in summer climatic condition for 24 h on different days on the month of April-May 2016.Different material in different mass are used in the basin to improve the heat capacity, radiation absorption capacity and enhance the evaporation rate. The heat transfer loss and the thermal efficiency are calculated for the different mass of these materials and finally compare with the conventional solar still. 100ml of Calcium chloride is the best basin material to improve the absorption, storage and evaporation rate since its shows the maximum efficiency of 64.88% when compare to the other material. KEYWORDS: Heat transfer coefficient, Absorbing material, solar radiation. I. INTRODUCTION Solar desalination is a process of separation of pure water from saline or sea water by using solar energy. The use of solar still is a cheap method of providing clean water. The solar assisted desalination system can be classified as: (i) passive (conventional) solar still and (ii) active (modified) solar still. The simple or conventional solar still consists of a black-painted copper or steel basin to receive solar radiation in which saline or sea water is kept. The basin is placed in a trapezoidal wooden box, which is covered by a glass cover at an angle between to the horizontal to retain the solar thermal energy inside the still due to greenhouse effect. That solar thermal energy is utilized to heat the saline or sea water. The space between the basin and wooden box is packed with glass wool insulation to reduce the heat loss through the sides and bottom of the still. Due to the existence of phase equilibrium between the saline water surface and air space, the air just over the water surface will be saturated with water vapour corresponding to the water erature. With the solar radiation incident on the saline water, its surface erature increases which causes the increase of saturated pressure of water vapour near the water surface corresponding to the water erature. At that time the partial pressure of water vapour near the glass surface will be less as the erature of the inner surface of the glass cover is lower than that of the water surface. The erature difference between the water and inner glass surface causes the difference in partial pressures of water vapour which causes the transfer of water vapour from the basin water surface to glass surface and the condensation on the inner surface of the glass. The rate of evaporation of water vapour from the water surface depends on the rate of condensation of water vapour in the glass cover. Even in the areas of higher solar intensity, the annual performance of the still per square meter of aperture is limited to an average of about L day -1. Interest in the conventional solar still has been due to its simple design, construction and low operating and maintenance cost, mainly in remote areas with no electricity supply. However, its low productivity simulates and motivates the researchers to develop novel methods to enhance the still productivity. A.S.Nafey[1] investigated that using a black rubber or black gravel material within a single sloped solar still as a storage medium improve a productivity by 20%at the condition of 60 l/m 2 by black rubber and improve the productivity by 19% at the condition of 20 l/m 2 by using black grave and 15 of glass cover each. Safwat Nafey[2] investigated the effect of using the floating perforated black plate on the two experiment still unit of 0.25 m 2 each. It is found that solar still increase productivity by 15 % (at brine depth of 3cm) and 40% (at brine depth of 6cm).Bilal A Akash[3] investigated that using different absorbing material like black rubber mat increased the daily water productivity by 37%,using black ink increased at by 45%, black dye enhance by 60%. A. A. El. Sebaii [4] investigated to decrease the preheating time of the basin water of basin type solar still, a single slope basin solar with baffle suspended absorber. Its result baffle absorber gives 20 % higher result productivity than normal single basin solar still without baffles. Bassam A/K Abu-Hijleh[5] investigated with different size sponge cube placed in the basin.it increased 18% to 273% compared to an identical still without sponge cubes.n.h.a Rahim[6] investigate a new approach is proposed to store excess heat energy in horizontal solar desalination still during the day time for the continuation of the process at night. This technique divide the horizontal still into evaporating and heat storing zone it is found 42.7 % of total amount of energy stored during the night. A.Tamimi[7] investigated that by operating with and without reflector and black bye under different condition still enhanced productivity considerably. O.O.Badran[8] investigated the still productivity increased up to 51 % when combined enhancer such as asphalt basin liner and sprinkler applied to the still. K.Kalidasa Murugavel [9] investigated by using wick material like cotton cloth, light jute cloth, sponge sheet, and natural rock. Cotton cloth gives better productivity when compare to other material. Rajesh Tripathi[10] investigated more yield is obtained during the off shine hours as compare for higher water depth due to storage effect. Numerous atts have been made by many researchers to increase the rate of evaporation of water and utilize the maximum solar energy that strikes on the still to enhance the system efficiency which utilizes a minimum amount of still surface. The main objectives of this experimental study is, (i) to find the effect of different mass of calcium chloride hexa hydrate and lauric acid on the performance and the internal and

2 external heat transfer of the single slope single basin solar distillation system. II. EXPERIMENTAL SETUP Two single basin solar stills are fabricated and tested under field condition at the testing field of the School of Electrical Engineering, Velammal engineering college, Tamilnadu, India. The basin liner is made of galvanized iron sheet of m 2 with maximum height of 288mm, and 1.4 mm thickness. The basin surfaces are painted with black paint to absorb the maximum amount of solar radiation incident on them. The condenser surface of the still is made of glass with 4mm thickness and angle of inclination is 10 with horizontal. There are certain specifications needed for the used glass cover in the still, and they are (a) Minimum amount of absorbed heat, (b) Minimum amount of reflection for solar radiation energy, (c) Maximum transmittance for solar radiation energy, and (d) high thermal resistance for heat loss from the basin to the ambient. Glass covers have been framed with wood and sealed with silicon rubber which plays an important role to promote efficient operation as it can accommodate the expansion and contraction between dissimilar materials. Figure 1 Pictorial views of Lauric acid and Calcium chloride hexa hydrate Figure 3 Schematic diagram of solar desalination still setup The experiments were performed in the April-May 2016 for typical days have been referred in this paper being the probable month of the year. The experiments were conducted on different three days in the campus of the Velammal Engineering college Chennai, India. All experiments were started at 9 AM local time and lasted for 24 h. In each day experiment constant water depth of 1 cas used. During experimentation when switching over from one absorbing material to another the still was left idle, minimum for a day to attain steady state condition Figure 2 Design parameter of Basin liner A collecting trough made by G.I. sheet is used in the still to collect the distillate condensing on the inner surfaces of the glass covers and to pass the condensate to a collecting flask. Steel rule is fixed along with inside for measuring water depths. The bottom and sides are insulated with 25mm thick thermocole and 12.5mm thick wood with thermal conductivity W/mK and W/mK respectively. The still technical specifications are shown in Table 1, and Fig.1. Fig 2, show the pictorial views of the various absorbing materials. Fig 3 shows the snap shot of the experimental setup Table 1 Technical specification of the solar still Figure 4 Experimental setup Prior to start of the experiment for next absorbing material till the completion of experiments for all absorbing material. The following parameters were measured every hour for a period of 24 h for fixed inclinations and for fixed water depth. Basin erature Back erature Side erature Water erature Glass erature Moist air erature erature Air Solar radiation Distillate output Water, Basin, glass and vapor eratures were recorded with the help of k-type thermocouples and a digital erature indicator having a least count of 0.1 C. Solar radiation is measured using pyranometer and the wind is measured using digital anemometer. And a 30mm steel rule is fixed inside used to measure water depth. And the readings were shown in table 2-5. III.THERMAL ANALYSIS OF SOLAR STILL The performance analysis is achieved by energy balance of the still. Fig.4 shows the energy transfer processes for various components in the still, which have a direct effect on the output.

3 Figure 5 Various components of conventional single slope solar still For simplifying the analysis, the following assumptions are considered: The level of water in the basin is maintained constant level. The condensation that occurs at the glass trough is a film type. The heat capacity of the glass cover, the absorbing material, and the insulation material are negligible. No vapor leakage in the still; The heat capacity of the insulator (bottom and side of the still) is negligible. We can obtain collecting efficiency of the still from writing energy balance equation for solar still, referring fig 1 I = Q d + Q rg + Q cg + Q bw + Q sw + Q bot (1) Q d, the amount of heat taken by distilled water, the expression is Qd =. h fg (2) Where, mass of output distilled water and h fg, latent heat of evaporation of water = 2382x10 3 J/kg Q cg, the convective heat transfer from glass to ambient is, Q cg = h cg A g (T g -T a ) (3) Where, h cg, convective heat transfer coefficient S.No Time I Table 2 Without using any latent heat material Basin Water Glass Side (Tsi) (Tb) (Tw) (Tg) Back (Tbi) between glass material and ambient. It is mainly depends on wind, the expression is, h cg =2+3.8V (4) Where, Q rg is the radiative heat transfer from glass to atmosphere, is equal to, Q rg = ε g Ag σ(t g 4 t s 4 ) (5) where ε g, emissivity of the glass material, σ, A g, surface area of glass exposed to atmosphere, Stefan Boltzmann constant, 5.67 x 10-8 K -4, h rg, radiation heat transfer coefficient between glass and air and T s, sky erature, is less than (such as 6 C) ambient erature Q bw, the heat transfer from inside to atmosphere through back, the expression is, Q bw =A bw *U*(T bwi T a ) (6) Where A bw Area of back, U - Overall heat transfer coefficient Q sw, the heat transfer from inside to atmosphere through side s, the expression is, Q sw =A sw *U*(T swi T a ) (7) Where A sw Area of side Where Q bot is the heat transfer rate from basin liner to atmosphere through bottoall, and It is expressed with composite conduction equation, the expression is, Q bot =A b *U*(T b T a ) (8) The thermal efficiency is η = Qd/ I (9) IV. OBSERVATION READING The reading are tabulated for different erature according to different time period without using any absorbing material.wind is measured by means of anemometer. Water, Basin, glass and vapor eratures were recorded with the help of k-type thermocouples and a digital erature Mass in ml Total The various measured erature and yield in passive mode for 30mater depth are taken for the conventional solar still without using any blue metal stone for each hour interval. Table 3 Using 70 ml of calcium chloride hexa hydrate S.No Time I Back (Tbi) Side (Tsi) Basin (Tb) Water (Tw) Glass (Tg) Mass in ml Total 1.1 The various measured erature and yield in passive mode for 1 cater depth are taken for the conventional solar still using 70 ml of calcium chloride hexa hydrate for each hour interval

4 S.N o Time I Back (Tbi) Table 4 using 100 ml of calcium chloride hexa hydrate Side Basin Water Glass (Tsi) (Tb) (Tw) (Tg) Mass in ml To tal The various measured erature and yield in passive mode for 1 cater depth are taken for the conventional solar still using 100 ml of calcium chloride hexa hydrate for each hour interval. Table 5 using 100 grams of lauric acid S.No Time I Back (Tbi) Side (Tsi) Basin (Tb) Water (Tw) Glass (Tg) Mass in ml Total.84 The various measured erature and yield in passive mode for 1 cater depth are taken for the conventional solar still using 100 grams of lauric acid for each hour interval Table 6 using 150 grams of lauric acid s.no Time I Back (Tbi) Side (Tsi) Basin (Tb) Water (Tw) Glass (Tg) Mass in ml total.955 The various measured erature and yield in passive mode for 1 cater depth are taken for the conventional solar still using 150 grams of lauric acid for each hour interval V. VARIOUS HEAT LOSSES WITH RESPECT TO TIME CASE 1:WITHOUT USING LATENT HEAT MATERIAL The graph is plot between the amounts of heat loss with respect to time period. The heat loss is calculated by the energy balance equation 2 to 8.The heat loss from bottom,side and back (Qbot,Qsw) is drastically increasing for every time period which will decrease the thermal efficiency of the still. The amount of distilled water during the off sunshine hour is less. Figure 6 Heat loss without using material The convective and radiative heat loss is linearly increased and after the 15 th hour it decrease. Since there is no absorbing material the latent heat of storage is absent which will reduce the thermal efficiency. CASE 2: BY USING 70 ML OF CALCIUM CHLORIDE HEXA HYDRATE

5 The heat loss from the bottom, side and back is similar to first case. The heat taken by the distilled water is high at 3 o clock which will increase the thermal efficiency. The heat loss from convective and radiative loss from glass is linear. The heat loss by radiative and convective is less when compared to bottom, side and back erature. The amount of distilled water is more during the off sunshine hours when compared to other material. CASE 5: BY USING 150 GRAMS OF LAURIC ACID Figure 7 Heat loss for 70 ml of Cacl 2 10h 2 0 CASE 3: BY USING 100 ML OF CALCIUM CHLORIDE HEXA HYDRATE Figure 10 Heat loss for 150 grams of lauric acid The heat loss during the 15 and 16 th is high in the back is increases. But in all three cases the heat loss from Qbot, Qsw and Qbw is similar.the heat loss for Qrg and Qcw is similar. But the thermal efficiency is better when comparing to case 4. VI. RESULT AND CONCLUSION Figure 8 Heat loss for 100ml of Cacl2 10h20 The heat loss from side and back is increasing in zig zag manner but it is more are less similar to the second case. The convective and radiative heat loss is less which will increase the thermal efficiency of the still. The heat taken by the distilled water is high at 3 o clock which will increase the thermal efficiency and the amount of distilled water during the off sunshine hour is more when compare to case 2 since it have more latent heat of storage. CASE 4: BY USING 100 GRAMS OF LAURIC ACID Figure 9 heat loss for 100 grams of lauric acid The heat loss from the bottom, side and back is increases but after the 13 th hour it get decrease. But in all the three case the Qbot, Qsw and Qbw is similar. The amount of heat taken by the distilled water is increases when the erature increases. The convective and radiative heat loss from glass to ambient air is decreasing after the 13 th hour during the off sun shine hour. But the thermal efficiency is comparatively less when compared to case 3 The thermal efficiency is calculated by using the equation 1 and 9.The results and discussions for the behavior and performance of the solar desalination system presented here in the form of graphs and tables. Experiments have been conducted from 9:00 hrs to 17:00 hrs. Experiments are conducted by considering a wide range of parameters such as eratures of basin water, erature of glass cover, hourly yield, erature of inside s (back and side ) and bottom side erature. At this particular condition, experiments were conducted for a number of days, so that analysis and comparison could be done fairly under the same climatic condition and to get concurrent results. And the amount of energy required to produce the distilled water (Q d ) is very high in all cases during 3 o clock. The mass of distilled water produced during the off sunshine hours is more while using 100 ml of calcium chloride hexa hydrate absorbing medium, this says that 100 ml material has high latent heat storage and releases it during the half peak hours. Heat losses froater surface to ambient through side and heat loss froater surface to ambient through bottom surface(qsw and Qbot) is similar in all cases. All the heat losses go on increasing as the time varies. And in this its concluded that 100 ml absorbing material has more thermal efficiency when compared with the other materials. This means that 100 ml material is more effective in converting saline water into distilled output and this material has better heat storage capacity when compared with other materials. REFERENCES 1. A.S.Nafey, M.Abdelkadar, Solar still productivity enhancement, Energy conversion and management

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