30120140505010

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30120140505010

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 99 STUDY OF EFFECT OF CONDENSING COVER MATERIALS ON THE PERFORMANCE OF A SOLAR STILL Parmendra Singh, Dr. Ajeet Kumar Rai, Vivek Sachan MED, SSET, Sam Higginbottom Institute of Agriculture Technology and Sciences, Allahabad (U.P.), India ABSTRACT In this work, an attempt has been made to study the effect of condensing cover material on the productivity of single basin solar still. Glass and acrylic sheet of 5 mm thickness were used as a condensing cover. Experiments were conducted on single basin single slope solar still with water depth of 1cm in the basin. Convective and evaporative heat transfer coefficients were calculated for 30 minutes time interval. When the glass is used as condensing cover daily energy and exergy efficiency were recorded as 36.43% and 2.73%, where as it is recorded as 16.84% and 1.52% when acrylic sheet used as a condensing cover. Keywords: Condensing Cover Materials, Energy and Exergy Efficiency. INTRODUCTION Desalination is a process to produce the distilled water from brackish/saline water for the use of medical, drinking and charging of the batteries, etc. purposes by using solar energy called solar still. The solar distillation systems are mainly classified as passive and active solar still. In passive solar still, the water in basin is heated directly by solar radiation i.e., without feeding an external energy but in active solar still an additional thermal energy is feed in to the basin of passive solar still to increase basin water temperature. One of the major challenges for putting solar still in practice is to work with the undesirable properties of glass as a material for mass production for solar stills [1]. Glass is heavy, brittle and has high replacement costs. On the other hand, plastic is light weight, relatively unbreakable, easy to transport and easy to process. Historically, plastic solar stills have been commercially more successful than glass solar stills and have sold over 400,000 units [2]. Still, due to higher amount of water production among other materials, glass has been the superior choice of material for its use as condensation surface inside a solar still. Factors like the type of material, roughness, inclination, INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 100 shape, transmittance, wiping and vibration of the condensing surface were found to have a significant impact on the production of water from the solar still [3-7]. The effect of condensing surface was covered in more detail [1-7]. The use of mechanically modified plastic against glass lowered the production of water by 18%[1]. The production of water from a solar still was found to be directly proportional to the thickness and thermal conductivity of condensing surface. The production of water decreased by 7% with an increase in glass thickness from 2 mm to 6 mm. The use of copper metal against plastic increased the production of water by 18%. [4] Dincer reported the relation between energy and exergy, exergy and environment, energy and sustainable development, and energy policy making and exergy in detail. The results obtain by Rosen et al[9]. suggested that exergy should be utilized by engineers and scientists, as well as decision making and policy makers, involved in green energy and technologies in tandem with other objectives and constraints. In the literature, the exergy analysis of a passive solar still is carried out by Nunez et al.[10] in Mexico. There are very limited studies on the exergetic evaluation of active solar desalination system in the literature. Garcia-Rodriguez and Gomez-Camacho[11] performed an exergy analysis of a solar multi- effect distillation system (SOL-14 plant) located in Almeria solar research centre in southeastern Spain. Similarly Sow et al.[12] carried out energetic and exergetic analysis of a triple effect distiller by solar energy. This work quantifies power consumption per unit mass of pure water. Show et al. obtain exergetic efficiencies between 16-26% for a triple effect system. The exergetic analysis has been widely used in design, simulation and performance evaluation of energy systems reported by Hepbsali[13]. Hepbasli[13] made a key review on exergetic analysis and assessment of renewable energy resources for sustainable future for solar collector, solar thermal power plant, solar cooker, solar drying, solar desalination and hybrid PV collector. In the present work a single slope solar still is tested with two different condensing cover materials experimentally and their energy and exergy analysis is also performed. EXPERIMENTAL SET-UP A prototype single slope solar still having a horizontal tray which acts as absorber of 1 m2 was designed and constructed. Tray was constructed using galvanized iron sheet of thickness 0.5 mm and later on painted in black. Testing was performed by placing the Single slope solar still operating in sunlight for a 24-h period. The work has led to the development of the single solar still and to a technical improvement. In order to achieve the maximum yield from the system, the still orientation should be the direction at which the highest average incident solar radiation is obtained. Experimental investigation of the Single slope solar still has shown that the productivity of the system was substantially increased in comparison with that of the basin type solar still. The present study was concerned with the energy and exergy efficiency based on evaporation from the water surface and based on condensation on the inner surface of the Single slope cover. Copper – constantan thermocouples are used, along with a digital temperature indicator, to record the glass temperature, water temperature and water vapor temperature in the experimental setup. These thermocouples, over a prolonged usage period, tend to deviate from the actual temperature. Therefore, they were calibrated with respect to a standard thermometer. A view of the condensing chamber and photograph of the experimental setup are shown in figure.1
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 101 Fig.1: Experimental setup of single slope solar Fig.2: Experimental setup of single slope solar Still with glass as a condensing cover still with acrylic as a condensing cover Performance of single slope solar still Energy efficiency Instantaneous efficiency The expression for instantaneous efficiency (ηi) ηi = ୫ୣ౭‫୐כ‬ ୍ሺ୲ሻ‫כ‬୅౭ Overall thermal efficiency The expression for overall thermal efficiency (ηpassive) ηpassive = ∑ ୫‫୐כ‬ ୟ౭୍ሺ୲ሻୢ୲ Exergy efficiency The general exergy balance for solar still can be written, Hepbalsi (2006) ΣExin - ΣExout = Exdes or Exsun – (Exevap + Exwork) = Exdest The exergy input to the solar still is radiation and can be written as Exsun = Exin =Aw * I (t)*[1 - ర య ( ౐౗ ౐౩ ) + భ య ሺ౐౗ ౐౩ ሻ4 ] The exergy output of a solar still can be written as Exevap =Aw* hew*(Tw – Tc )*[1 -ሺ ౐౗ ౐౭ ሻ] The exergy of work rate for solar still Exwork = 0 The exergy destructed in solar still can be written as Exdest = Mw*Cw *(Tw – Ta)*[1 -ሺ ౐౗ ౐౭ ሻ] The exergy efficiency of solar still us defined, Hapbalsi (2006) ηex = ୉୶ୣ୰୥୷ ୭୳୲୮୳୲ ୭୤ ୱ୭୪ୟ୰ ୱ୲୧୪୪ ୉୶ୣ୰୥୷ ୧୬୮୳୲ ୭୤ ୱ୭୪ୟ୰ ୱ୲୧୪୪ ሺ୉୶౛౬౗౦ሻ ሺ୉୶౟౤ሻ
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 102 RESULTS AND DISCUSSION Number of readings was taken on the setup and data were analyzed for two different days in a month. Fig.3: Variation of Solar intensity with time of a day Fig.3 shows the Variation of solar intensity with time on two different days of experimentation in the month of April. Fig.4: Variation of wind speed with time of a day 0 200 400 600 800 1000 1200 1400 Solarintensity(w/m2) Time of a day (hr) I(t)a I(t)g 0 1 2 3 4 5 6 Windspeed(m/s) Time of a day (hr) Va Vg
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 103 Fig.4 shows the Variation of wind speed with time on two different days of experimentation under consideration. Average wind speed on 01/04/2014 was 2.4166 and average wind speed on 23/04/2014 was 1.411 m/s. Fig.5: Variation of temperature with time of a day Fig.5 shows the Variation of temperature with time, water temperature with acrylic condensing cover is higher than water temperature with glass cover. Inner condensing cover temperature of acrylic sheet is higher than that of glass cover. Fig.6: Variation of convective heat transfer with time of a day 0 10 20 30 40 50 60 70 80 Temprature0C Time of a day Twg Tag Tgi Twa Taa Tai 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Evaporativeheattransfer coefficient(w/m2) Time of a day(hr) hcwa(PM) hcwa(DM) hcwg(PM) hcwg(DM)
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 104 Fig.6 shows the variation of convective heat transfer coefficient with time. Evaporative heat transfer coefficient (PM) is higher than evaporative heat transfer coefficient (DM). Fig.7: Variation of evaporative heat transfer coefficient with time Fig.7 shows the variation of convective heat transfer coefficient with time. Evaporative heat transfer coefficient is higher when glass is used as condensing cover. The maximum value of exergy efficiency of glass cover is 6.64% whereas it is 3.54% for acrylic sheet condensing cover. Fig.8: Variation of energy efficiency with time of a day 0 10 20 30 40 50 60 70 80 90 100 Evaporativeheattransfer coefficient(w/m2) Time of a day(hr) hewa(PM) hewa(DM) hewg(PM) hewg(DM) 0 10 20 30 40 50 60 Energyefficiency(η) Time of a day (hr) ηg ηa
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 105 Fig.8 shows the variation of energy efficiency with time. Energy efficiency is higher when glass is used as a condensing cover. The maximum value of energy efficiency of glass cover is 50.37% whereas it is for acrylic sheet condensing cover 29.13%. Fig.9: Variation of exergy efficiency with time of a day Fig.9 shows the variation of exergy efficiency with time. Exergy efficiency is higher when glass is used as condensing cover. The maximum value of exergy efficiency of glass cover is 6.64% whereas it is for acrylic sheet condensing cover 3.54%. Fig.10: Variation of distillate with time of a day 0 1 2 3 4 5 6 7 ExergyEfficiency(η) Time of a day (hr) Exa Exg 0 0.1 0.2 0.3 0.4 0.5 0.6 Distillate(kg) Time of day(hr) mthg mexpg mtha mexpa
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 106 Fig.10 shows the theoretical and experimental distillate with time for glass and acrylic sheet used as a condensing cover. Fig.11: Variation of distillate with time of a day Fig.10 shows the variation of experimental distillate output with time. It is observed that the daily productivity is higher when glass is used as the condensing cover than acrylic sheet condensing cover. A maximum of 3.925 liter/day is obtained with glass cover in comparison to 2.310 liter/day when acrylic sheet is used. CONCLUSION A single slope solar still with different condensing cover material is tasted in the premises of SHIATS-DU Allahabad. Energy and Exergy analysis of the system is performed to find the maximum energy efficiency and exergy efficiency of the system. The following points can be concluded from the present work. • The exergy efficiency of a single slope solar still is lower than energy efficiency it is due to lower evaporative heat transfer rate. • The maximum instantaneous energy efficiency for solar still with glass as a condensing cover is 50.30% when as it is 29.136% for acrylic sheet condensing cover. • The maximum instantaneous energy efficiency for solar still is 6.64% when glass is used as a condensing cover and 3.54% when acrylic sheet condensing cover. • Daily productivity increased by 71% when glass is used for condensing cover. REFERENCES [1] Howe Tleimat, Comparison of plastic and glass condensing covers for solar distillers, 12 (1969) 293–304. [2] H.R. Hay, Plastic solar stills: past, present and, future, 14 (1973) 393–404. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Distillate(kg) Time of day(hr) pa pg
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 99-107 © IAEME 107 [3] A.K. Tiwari, G.N. Tiwari, Annual performance analysis and thermal modeling of passive solar still for different inclinations of condensing cover, Desalination (2007) 1358–1382. [4] V. Dimri, B. Sarkar, U. Singh, G. Tiwari, Effect of condensing cover material on yield of an active solar still: an experimental validation, Desalination 227 (2008) 178–189. [5] G.N. Tiwari, J.M. Thomas, E. Khan, Optimization of glass cover inclination for maximum yield in a solar still, Heat Recov. Syst. CHP 14 (1994) 447–455. [6] J. Pieters, J. Deltour, M. Debruyckere, Light transmission through condensation on glass and polyethylene, Agr. Forest. Meteorol. 85 (1997) 51–62. [7] B. Cemek, Y. Demir, Testing of the condensation characteristics and light transmissions of different plastic film covering materials, Polym. Test. 24 (2005) 284–289. [8] M.A. Rosen, I Dincer and M. Kanoglu, Role of exergy in increasing efficiency and sustainability and reducing environmental impact, Energy Policy,(36)1 (2007) 128-137. [9] J.C.T.Nunez, M.A.P. Gandara and J.G.C.D. Gortari, Exergy analysis of a passive solar still, Renewable Energy, 33 (2008) 608-616. [10] L. Garcia-Rodriguez and C. Gomez-Camacho, Exergy analysis of the SOL-14 plant, Desalination, 137 (2001) 251-258. [11] O. SOW, M. Siroux and B. Desmet, Energetic and exergetic analysis of a triple effect distiller driven by solar energy, Desalination, 174 (2005) 277-286. [12] A.Hepbasli, A. key review on exegetic analysis and assessment of renewable energy sources, Renewable and Sustainable Energy Reviews, 12 (2008) 593-661. [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] 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. [15] 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. [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] 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. [18] Ihsan Mohammed Khudhur and Dr. Ajeet Kumar Rai, “Experimental Study of a Tubular Solar Still Integrated with a Fan”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 5, Issue 3, 2014, pp. 1 - 8, ISSN Print: 0976-6480, ISSN Online: 0976-6499. [19] Hasan Falih M., Dr. Ajeet Kumar Rai, Vivek Sachan and Omar Mohammed I., “Experimental Study of Double Slope Solar Still with Energy Storage Medium”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 5, Issue 3, 2014, pp. 147 - 154, ISSN Print: 0976-6480, ISSN Online: 0976-6499.

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