30120140506005

233 views

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
233
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
3
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

30120140506005

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 47 ENERGY AND EXERGY ANALYSIS OF A DOUBLE SLOPE SOLAR STILL Ankur Kumar 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 perform energetic and exergetic analysis of a double slope solar still. Experiments were performed on a single basin double slope solar still in the premises of SHIATS-DU Allahabad. Energy and exergy balance equations were written for the system. It is observed that the energy efficiency of the system with south glass cover is higher than that of north side glass cover, whereas exergy efficiency of the system with north cover is higher than that of the system exergy efficiency with south side glass cover.The daily energy efficiency of the system is 29%. INTRODUCTION Supplying of fresh water is an urgent need for drinking, cleaning, agriculture and domestic usages. Nowadays, remote areas and arid zones suffer from water scarcity. Surveys reveal that about 79% of available water is salty, only 1% is fresh and the rest 20% is brackish [1]. Desalination is a process in which fresh water is produced from saline water. Solar stills are used for water desalination in remote areas and rural places with low congestion and limited demand. Direct solar stills use the solar energy to produce distillate directly in the solar collector and the system that combine conventional desalination system with solar collector are called indirect systems [2]. The various forms of energy are due to random thermal motion, kinetic energy, potential energy associated with a restoring force, or the concentration of species relative to a reference state. Exergy analysis provides a method to evaluate the maximum work extractable from a substance relative to a reference state (i.e dead state).The reference state is arbitrary ,but for terrestrial energy conversion the concept of exergy is most effective if it is chosen to reflect the environment on the surface of earth. Solar radiation is free, abundant, easily available and need no transportation. Distillation is a natural phenomenon. Solar energy heats water source, evaporates it and condenses by clouds and back to the earth as rainfall. Solar stills are simulating this natural process in small scale. In order to establish how much work potential a resource contains, it is necessary to compare it a against a state INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 6, June (2014), pp. 47-54 © 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 6, June (2014), pp. 47-54 © IAEME 48 defined to have zero work potential. An equilibrium environment which cannot undergo an energy conversion process to produce work is the technically correct candidate for a reference state [3].Exergy is the expression for loss of available energy due to the creation of entropy in irreversible systems or processes. The exergy loss in a system or component is determined by multiplying the absolute temperature of the surroundings by the entropy increase. Entropy is the ratio of the heat absorbed by a substance to the absolute temperature at which it was added. While energy is conserved, exergy is accumulated [4]. EXPERIMENTAL SET-UP Fig shows the photograph and schematic diagram of a double slope solar still. The experimental setup consists of a passive solar distillation unit with a glazing glass cover inclined at 2605having an area of 0.048m x 0.096 m. This tilted glass cover of 3 mm thickness, served as solar energy transmitter as well as a condensing surface for the vapor generated in the basin. Glass basin, made up of Galvanized Iron, has an effective area of 0.72 m2. The basin of the distiller was blackened to increase the solar energy absorption. A distillate channel was provided at each end of the basin. For the collection of distillate output, a hole was drilled in each of the channels and plastic pipes were fixed through them with an adhesive (Araldite). An inlet pipe and outlet pipe was provided at the top of the side wall of the still and at the bottom of the basin tray for feeding saline water into the basin and draining water from still for cleaning purpose, respectively. Rubber gasket was fixed all along the edges of the still. All these arrangements are made to make the still air tight. Water gets evaporated and condensed on the inner surface of glass cover. It runs down the lower edge of the glass cover. The distillate was collected in a bottle and then measured by a graduated cylinder. The system has the capability to collect distillates from two sides of the still (i.e. East & West sides and North & South sides). Thermocouples were located indifferent places of the still. They record different temperature, such as inside glass cover & water temperature in the basin and ambient temperature. In order to study the effect of salinity of the water locally available, table salt was used at various salinities. All experimental data are used to obtain the internal heat and mass transfer coefficient for double slope solar still. Fig 1: Experimental Setup of a Double Slope Solar still
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 49 Performance of double 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 ୅౭୍ሺ୲ሻୢ୲ Exergy analysis The general exergy balance for solar still can be written, Hepbalsi (2006) 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୉୶ୣ୴ୟ୮ሻ ሺ୉୶୧୬ሻ ηEx = 1 - ୉୶ୢୣୱ୲ ୉୶୧୬ hcw=.884[(Tw-Tg)+(Pw-Pg)(Tw+273)/268.9x103 -Pw]1/3 hew=.01623.hcw.(Pw-Pg)/(Tw-Tg) RESULTS AND DISCUSSION Fig.2: Variation of Solar Intensity with time of a day 0 200 400 600 800 1000 1200 1400 8:30 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 SolarIntensity(W/m2) Time of a day(hr) Solar Intensity(N) Solar Intensity(S)
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 50 Figure 2 shows the variation of solar intensity on the north side glass cover and south side glass cover with time of a day. Solar intensity continuously increased and reached its maximum value in the noon on the both side of the glass cover since south side glass cover is facing sun so these two covers distant except evening and morning. Fig.3: Variation of Wind Speed with time of a day Figure 3 shows variation of wind velocity on a particular day of experiments in the month of may. Fig.4: Variation of Temperature with time of a day Figure 4 shows variation of temperature of south side glass, north side glass, water, ambient. Water temperature is always higher than glass temperature. A max value of water temperature of 530 c is reached at around 2 o’clock. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 WindSpeed(m/s) Time of a day(hr) WIND SPEED 0 10 20 30 40 50 60 Temperature(0C) Time of a day(hr) Temperatue(S) Temperatue(N) Temperatue(W) Temperatue(A)
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 51 Fig.5: Variation of Distillate with time of a day Figure 5 shows the variation of distillate outfut for north and side glass cover. Distillate for north side glass cover is higher than south side glass cover because of temperature difference between water and glass is higher than temperature difference between water and south side glass. Fig.6: Variation of Convective Heat Transfer Coefficient with time of a day Figure 6 shows variation of convective heat transfer coefficient for north side is higher than convective heat transfer of south side. Average value of convective heat transfer coefficient for north and south side are 1.85W/m2 K and 1.57W/m2 K. 0 10 20 30 40 50 60 70 80 90 100Distillate(ml) Time of a day(hr) Distillate(N) Distillate(S) 0 0.5 1 1.5 2 2.5 3 ConvectiveHeatTransferCoefficient (W/m2K) Time of a day(hr) Convective Heat Transfer Coefficient(N) Convective Heat Transfer Coefficient(S)
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 52 Fig.7: Variation of Convective Heat Transfer Coefficient with time of a day Figure 7 shows variation of evaporative heat transfer coefficient for north side is higher than evaporative heat transfer of south side. Average value of evaporative heat transfer coefficient for north and south side are 12.30W/m2 K and 12.00m2 K. Fig.8: Variation of Energy Efficiency with time of a day Figure 8 shows variation of daily efficiency of north side is 51.11% and south side is 19.62%. 0 5 10 15 20 25 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 EvaporativeHeatTransferCoefficient (W/m2K) Time of a day(hr) Evaporative Heat Transfer Coefficient(N) Evaporative Heat Transfer Coefficient(S) 0 10 20 30 40 50 60 70 80 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 EnergyEffiicency Time of a day(hr) Energy Efficency(N) Energy Efficency(S)
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 53 Fig.9: Variation of Exergy Efficiency with time of a day Figure 9 shows variation of daily exergy efficiency of north side is 0.64% and south side is 0.81 %. CONCLUSION The following points can be concluded from the present work. • The energy efficiency for solar still with glass as a condensing cover for north and south are 51.11% and 19.63%. • The exergy efficiency for solar still with glass as a condensing cover for north and south are 0.64% and 0.81%. • The exergy efficiency of solar still is lower than energy efficiency due to lower evaporative heat transfer rate. 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. [3] Hermann WA. Quantifying global exergy resources. Energy 2006;31(12):1685–702. [4] Kilkis IB. Utilization of wind energy in space heating and cooling with hybrid. Energy Buildings 1999;30:147–53. [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. 0 2 4 6 8 10 12 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 4:30 5:00 ExergyEfficiency Time of a day(hr) Exergy Efficiency(N) Exergy Efficency(S)
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 6, June (2014), pp. 47-54 © IAEME 54 [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] Hermann WA. Quantifying global exergy resources. Energy 2006; 31(12):1685–702. [14] Kilkis IB. Utilization of wind energy in space heating and cooling with hybrid. Energy Buildings 1999; 30:147–53. [15] 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. [16] 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. [17] 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. [18] 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. [19] 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. [20] 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. [21] 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. [22] Parmendra Singh, Dr. Ajeet Kumar Rai and Vivek Sachan, “Study of Effect of Condensing Cover Materials on the Performance of a Solar Still”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 5, Issue 5, 2014, pp. 99 - 107, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [23] 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. [24] 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.

×