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20120140503001

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  • 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 1 EXPERIMENTAL STUDY OF A TUBULAR SOLAR STILL INTEGRATED WITH A FAN Ihsan Mohammed Khudhur*, Dr. Ajeet Kumar Rai** *Technical College Kirkuk, Foundation of Technical Education, Ministry of Higher Education and Scientific Research, Republic of Iraq **Department of Mechanical Engineering SSET, SHIATS- DU Allahabad (U.P) INDIA- 211007 ABSTRACT In this commutation, an attempt has been made to increase the productivity of a tubular solar still. A tubular solar still was designed fabricated and tested in the Allahabad climatic conditions. Basin was made up of GI sheet and painted black to increase its absorptivity. Condensing cover made of polycarbonate sheet. Number of experiment was conducted to read the behavioral variation inside the still. A fan is used to increase the rate of evaporation and condensation inside the still. It is observed that by using fan inside the still, daily productivity increased by 8.5%. Keywords: Tubular Solar Still, Condensing Cover Temperature, Heat & Mass Transfer Coefficient. INTRODUCTION Water production from a solar still is expressed as the amount of produced distilled water per day per unit of basin surface. Water production depends strongly by the amount of the falling solar energy. In a given location, it depends by the existing climatic conditions and the time of the day and year. So, it takes maximum values during sunny and warm days of summer and midday and it takes minimum values in winter time. Since solar energy per unit surface is standard by nature, production of a given installation increases only with the increase of the surface of the still. The output of a one-stage solar still is within 1-2 l/m2 per basin area per day in winter time and within 3-4 l/m2 per basin area per day for summer time(Cooper,1969, .Malik et. al, 1982, E.E. Delyannis, 1991,Guinn, 1992, O.A. Hamed, et. Al., 1993). Efficiency of solar stills varies in the range of 25- 40% in winter time and in the range of 30-60% in summer time, depending of course on the design, construction and environmental and operating conditions. INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET) ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 5, Issue 3, March (2014), pp. 01-08 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2014): 4.1710 (Calculated by GISI) www.jifactor.com IJARET © I A E M E
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 2 The solar distillation systems, which differ mainly in the geometry of the distillation unit, in the used materials and in the several techniques for the increase of output, are continuous objects of research work. However, all designs and types are based on the same operation principle. The simplest unit for solar distillation is the one-stage solar still. These units are placed either in the ground or on bases. The low productivity of solar stills has leaded the researchers to several efforts to increase productivity. These are focused on the design of the several parts of the solar still, concerning the geometry, the material, the operating parameters or the use of techniques to increase productivity. Tubular Solar Still (TSS) consists of a transparent tubular cover made of polycarbonate and a trough inside the cover. Consequently, the weight of the TSS became much lighter than that of the basin type with a glass cover. The TSS, therefore, can be easily built on-site without using special tools. This easy assembly helps shortening of water transportation distance. The scope of the efforts on the design of the solar still is to find the optimum parameters concerning the productivity of the solar still. A basic parameter in the output of solar stills is their geometry, mainly concerned on the shape and the slope of the transparent cover. For the determination of the slope of the cover the installation area, the volume of the air-tight area inside the still and the type of the cover material have to be taken into account. Transmittance of the material takes the maximum values when solar radiation falls vertically on the cover, whereas it is decreased significantly with the increase of incidence angle of solar radiation. For the mild climate zones this means large volumes of air-tight area inside the still, which decreases the output. On the contrary, small slopes mean smaller volumes of air-tight area inside the still which increases output, however there is the danger of increased losses due to the falling of water condensate back to the mass of the saline water in the basin before it is collected as output. It has been reported that there is an optimum slope of the cover, concerning the water production. This lies between 100 and 250 for regions with mild climate, whereas for hot regions it is between 350 Akash, et al., (2000). But in other reports it is said that in hot regions the optimum slope of the still cover is around 150 (S. Kumar et al. 2000). Moreover, the thickness of the cover plays important role in the output because the increase of thickness means decrease of the transmittance of the cover to solar energy. It has also been reported that the increase of thickness causes reduction on the output larger than the output that would mean the respective reduction of the transmittance of the cover. Finally, the use of double cover reduces the output by 25-30% and it increases also the cost of the solar still. The output of the solar still increases when the distance between the basin and the surface where condensation takes place decreases (Satcunanathan and Hansen, 1973). However, in some other experiments it has been seen that the influence of this distance is not crucial for low values of solar radiation. The material of the basin plays important role in the output of the solar still. It has been reported that the use of black plastic wick increase the output by 38 - 60%. Akash, et al., (1998). Other absorbing materials for the still basin, black rubber can also be used with an increase of output of about 20%. Generally speaking, the increase of the absorptance of the basin material increases the still output. The depth of the saline water is also an important factor for the still output. It has been reported that it does not play important role in well insulated stills, but it has significant influence in not insulated ones, especially in smaller depths ( Fath, 1996; Kumar, et al., 2000). It has been reported also that for water depth of more than 10 cm there is not essential change in the distilled water productivity, when all other parameters are kept steady. Insulation of the basin plays important role in the output of the system, and its effect is seen mainly in smaller water depths. It has been shown that the decrease of the heat loss coefficient through the bottom and the sides from the value of 4 W/m2 C to the value of 2 or 1 W/m2 C it brings an increase in water production by 20% or 34% respectively Fath, (1996). The effect of climatic parameters wind on the performance of a single basin type solar still has been studied by different researchers. Soliman, (1972), has studied the effect of water and ambient temperatures, wind velocity and angle of inclination of the cover on the performance of the still is shown by means of tables and
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 3 graphs. This leads to the explanation that at low water temperatures, the rate of evaporation is low. Whereas at high water temperatures, increasing wind speed will increase the ratio of rate of evaporation to the total heat transfer through the cover. Nafey, et al., (1997), has studied the various parameters affecting the solar still productivity. In this work, investigation of the main parameters affecting solar still performance under the conditions of Suez gulf was considered. A general equation relating the dependent and independent variables which control the daily productivity of a single slope solar still is developed. This equation could be used to predict the daily productivity with a reasonable confidence level (max. error ±5%). Hinai, et al. (2002) formulated a mathematical model to predict the productivity of a simple solar still under different climatic, design and operational parameters in Oman. The shallow water basin, 230 cover tilt angle, 0.1 m insulation thickness and asphalt coating of the solar still were found to be the optimum design parameters that produced an average annual solar still yield of 4.15 kg/m2 day. Investigators’ ideas about the effect of wind on solar stills vary (telkes,1956; Lof et al. 1961; Hollands 1963) state that increasing wind velocity causes a decrease in the output Cooper (1969) points out that increasing wind velocity causes an increase, the influence of wind on output is unimportant. that wind blowing over the glass cover causes faster evaporation. As the wind velocity increases, the convective heat transfer coefficient from the glass cover to ambient air increases and simultaneously the glass cover temperature decreases. Due to this, the temperature difference between water surface and the glass cover increases and ultimately the yield of the solar still increases as compared to stagnant ambient air conditions. As the wind velocity over the solar still increases, the distillate yield of the solar still increases continuously. The wind velocity is more effective in summer and at higher water masses and it was found tobe10and8m/s on typical summer and winter days, respectively .It was found that productivity increases with the increase of wind speed up to atypical velocity beyond which the increase in productivity becomes insignificant El-sebaii (2000) EXPERIMENTAL SETUP A prototype solar still having a horizontal tray which acts as absorber of 0.62 m2 was designed and constructed rai et al. (2013). Tray was constructed using galvanized iron sheet of thickness 0.5mm and later on painted in black. The try is surrounded by tubular structure made up of Polycarbonate sheet. The total area of the Polycarbonate cover is 2.6 m2 . The still is formed a tubular transparent surface made up of Polycarbonate sheet. Testing was performed by placing the tubular solar still operating in sunlight for a 24-h period. The work has led to the development of the tubular solar still and to an orientation should be the direction at which the highest average incident solar radiation is obtained. Experimental investigation of the tubular solar still has shown that the productivity of the system was substantially increased in comparison with that of the other type of basin type solar still. The present study was concerned with the modified design of TSS and development of models with improved rate of evaporation and condensation on the inner surface of the tubular cover. Copper-Constantan thermocouples are used, along with a digital temperature indicator, to record the condensing cover temperature, water temperature and water vapor temperature in the experimental setup. These thermocouples, over a prolonged usage period, tend to deviate from the actual data. Therefore, they were calibrated with respect to a standard thermometer. A view of the condensing chamber and photograph of the experimental set up are shown in figure. 1. To find the effect of addition of a fan in the TSS, number of readings was taken on this setup for different seasons of Indian climatic conditions. For a particular day in the month of February, readings taken with and without the addition of a fan are shown in the table 1and table 2.
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 4 Fig.1. Photograph of Tubular Solar Still Table 1: Observations without fan in Tubular solar still T TIME T1 ˚ GLASS T2 ˚ GLASS T3 ˚ BASIN T4 ˚ WATER T5˚ INLET FPC T6 ˚ OUTLET FPC T7˚ VAP UP T8˚ VAP DOWN T9˚ AMB. air WIND Velocity M/S Distal ltion ML Solar Intens. MW/2 08:30 22 19 26 27 39 32 30 26 19 0.5 0 34 09:00 33 26 30 31 39 46 45 30 21 0.5 10 42 09:30 38 29 34 34 39 61 52 33 23 0.8 34 54 10:00 42 32 38 39 39 75 61 36 24 1.1 35 61 10:30 48 35 43 43 40 80 62 37 25 1.0 47 74 11:00 50 37 46 46 41 83 72 40 25 1.0 66 82 11:30 52 39 49 49 41 83 74 42 26 1.0 87 84 12:00 54 41 50 50 41 83 75 42 27 1.0 99 88 12:30 56 43 52 52 43 84 76 44 28 1.2 118 91 01:00 54 41 51 51 43 83 74 43 29 1.0 121 86 01:30 53 42 53 52 46 83 75 44 30 1.0 125 85 02:00 52 42 52 52 48 83 76 44 31 1.2 120 77 02:30 48 41 51 51 50 81 74 44 32 1.1 116 68 03:00 49 41 50 50 51 74 61 43 31 1.5 106 57 03:30 46 41 49 49 52 71 70 42 30 1.1 95 42 04:00 42 39 47 47 52 62 67 41 29 1.0 87 31 04:30 36 34 42 42 51 51 61 39 27 1.0 64 19 05:00 32 31 38 39 51 41 58 36 26 1.0 48 9
  • 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 5 Table 2: Observations with fan in Tubular solar still RESULTS AND DISCUSSION The variation of vapor temperature inside the solar still above and below the basin at a water depths of 2 cm are shown in fig.2. As the vapor leaves the water surface its tendency is to rise up, it reaches to top cover surface and starts condensing. The presence of vapor particle below the basin are less, due to this reason temperature below the basin is low which is shown in fig. 2 by Tbb ( temperature of vapor below the basin). A large temperature difference exit between temperature of vapor above the basin and temperature below basin. Fig. 2: Variation of Temperature with and without fan with time of a day on 12 February 2014 water depth 2 cm T TIME T1 ˚ GLASS T2 ˚ GLASS T3 ˚ BASIN T4 ˚ WATER T5˚ INLET FPC T6 ˚ OUTLET FPC T7˚ VAP UP T8˚ VAP DOWN T9˚ AMB. air WIND Velocit M/S Distal ltion ML Solar Intens. MW/C M2 08:30 22 17 15 15 40 42 28 21 14 0.8 0 33 09:00 31 22 24 25 40 61 33 26 16 0.8 20 52 09:30 33 24 27 27 40 72 31 29 18 1.0 35 65 10:00 38 27 32 32 41 83 37 33 18 1.3 45 70 10:30 42 30 37 36 42 84 41 36 19 1.2 50 74 11:00 45 31 41 39 42 89 43 39 20 1.4 63 82 11:30 47 33 43 42 42 90 45 40 21 1.3 80 90 12:00 49 34 45 43 44 85 47 41 22 1.2 109 96 12:30 51 37 48 46 46 89 52 40 23 1.3 115 94 01:00 51 38 49 47 48 82 54 41 24 1.5 117 88 01:30 49 36 48 46 47 81 52 40 25 1.2 122 84 02:00 46 36 48 46 45 80 58 40 26 1.1 144 79 02:30 46 36 47 45 45 80 47 39 25 1.4 115 71 03:00 43 36 46 45 46 81 44 39 24 1.7 110 62 03:30 38 32 43 42 45 73 42 38 24 1.7 107 52 04:00 36 31 41 40 45 62 41 38 24 1.1 100 42 04:30 31 28 38 36 45 53 40 38 23 1.2 99 22 05:00 28 26 35 33 45 39 36 35 22 1.2 65 9
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 6 Fig. 2 shows the varation temperature of vapor above the basin and below the basin inside the basin with and without fan at water depth of 2 cm. Temperature of above the basin is higher without fan than Temperature of vapor above the basin with fan because of forced convection inside the still. Fig.3: Variation of temperature with and without fan with time of a day on February 2014 water depth 2 cm Fig.3 shows the temperature of cover with and without fan. Cover temperature decreases when fan is used. A maximum of 15% temperature of the cover is reduced by using the fan. Temperature of vapor above the basin is higher without fan than Temperature of vapor above the basin with fan. Because of air velocity temperature of condensing cover decrease which increase ∆T(TW-TC). Which increase the total productivity of the still. Fig. 4: Variation of Productivity with and without fan February 2014 water depth 2 cm Fig.4 shows the productivity of tubular solar still in natural convection mode and in forced convection mode. Forced convection is induced inside the still with the addition of a fan. It is observed that the day time productivity increase by 8.56%and for night productivity is increased by 7.95%
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 7 CONCLUSION A modified tubular solar still is designed, fabricated and tested in Allahabad climatic condition. Temperature above the basin and below the basin are quiet different inside the tubular solar still. A fan is used to push the vapor from hot zone towards the cold zone and towards the condensing cover side thereby increasing the rate of evaporation and condensation inside the tubular solar still. An increase in water temperature and decrease in condensing cover temperature is recorded. Day time productivity increases by 8.56% and with use of this fan night time production increases by7.95%. REFERENCES [1] Malik M.A.S. G. Tiwari, A. Kumar, M. S. Sodha, “Solar Distillation”, Pergamon Press, 1982. [2] Delyannis E.E. (1991)``Historic background of desalination``, Proc. New Technologies for the use of Renewable Energy Sources in Water Desalination, pp. 1-11, DG XVII, CRES, Athens, 1991. [3] Guinn G.R., “Field test evaluation of solar-heated evaporators”, Journal of Solar Energy Engineering, vol 114, pp. 165-170, 1992. [4] Hamed O.A. E, Eisa, W.E. Addalla, “Overview of solar desalination”, Desalination 93, 1993. [5] Soliman, S. H. “Effect of wind on solar distillation”, Solar Energy, Vol.13, pp.403-415, 1972 [6] Nafey, A.S. M. Abdelkader, A. Abdelmotalip and A.A. Mabrouk, “Parameters affecting solar still productivity”, Energy Conversion and Management, Vol.41, pp.1997-1809, 2000. [7] Hinai, H.Al. M.S. Al-Nassri and B.A. Jubran, “Effect of climatic, design and operational parameters on the yield of a simple solar still”, Energy Conversion and Management, Vol.43, pp.1639-1650, 2002. [8] Telkes, M. Res. Dev. Prog. Report No. 13, Dec. 1956. [9] Hepbasli A, Dincer I, Rosen MA. Exergy analysis of heat pump systems for residential applications. In: CD-Proceedings of seventh international HVAC+R technology symposium, Istanbul, Turkey, 8–10 May 2006. [10] Ajeet Kumar Rai, Ashish Kumar and Vinod Kumar Verma, “Effect of Water Depth and Still Orientation on Productivity of Passive Solar Still”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 740 - 753, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [11] Cooper, P.I “Digital simulation of transient solar still processes”, Solar Energy, Vol.12, pp.313, 1969. [12] Ajeet Kumar Rai, Vivek Sachan and Maheep Kumar, “Experimental Investigation of a Double Slope Solar Still with a Latent Heat Storage Medium”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 1, 2013, pp. 22 - 29, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [13] Ajeet Kumar Rai, Pratap Singh, Vivek Sachan and Nripendra Bhaskar, “Design, Fabrication and Testing of a Modified Single Slope Solar Still”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 4, 2013, pp. 8 - 14, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [14] Lof, G.O.G. J. A. Eibling and J. W. Bloemer, “Energy balances in solar distillers”, A.I.Ch.E.J. 7, No. 4, 1961. [15] Hollands, K.G.T. “The regeneration of lithium chloride brine in a solar still for use in solar air conditioning” Solar Energy, Vol.7, Issue 39, 1963.
  • 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 3, March (2014), pp. 01-08, © IAEME 8 [16] Ajeet Kumar Rai, Nirish Singh and Vivek Sachan, “Experimental Study of a Single Basin Solar Still with Water Cooling of the Glass Cover”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 6, 2013, pp. 1 - 7, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [17] Morse P. N. and W.R.W. Read, “A rational basis for the engineering development of a solar still”, Solar Energy, Vol.12, Issue 1, pp 5-17, 1968. [18] El-sebaii AA, Effect of wind speed on some designs of solar stills. Energy Conversion and Management 2000; 41(6):523–38. [19] Satcunanathan, S. H.P. Hansen, "An investigation of some of the parameters involved in solar distillation", Solar Energy, 14, pp.353-363, 1973. [20] Kumar,S. G.N. Tiwari, H.N. Singh, “Annual performance of an active solar distillation system”, Desalination, 127, pp. 79-88, 2000. [21] Fath, H.E.S. “High performance of a simple design, two effect solar distillation unit”, Desalination, 107, pp. 223-233, 1996. [22] B.A. Akash, M.S. Mohsen, W. Nayfeh, “Experimental study of the basin type solar still under local climate conditions”, Energy Conversion & Management, 41, pp. 883-890, 1998. [23] Ajeet Kumar Rai, Vivek Sachan and Bhawani Nandan, “Experimental Study of Evaporation in a Tubular Solar Still”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 2, 2013, pp. 1 - 9, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.