EXPERIMENTAL STUDY OF A TUBULAR SOLAR STILL WITH PHASE CHANGE MATERIAL

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1 INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) International Journal of Mechanical Engineering and Technology (IJMET), ISSN (Print), ISSN (Print) ISSN (Online) Volume 6, Issue 1, January (215), pp IAEME: Journal Impact Factor (214): (Calculated by GISI) IJMET I A E M E EXPERIMENTAL STUDY OF A TUBULAR SOLAR STILL WITH PHASE CHANGE MATERIAL Ajeet Kumar Rai, Vivek Sachan Mechanical Engineering Department, SSET, SHIATS Allahabad (UP) India ABSTRACT Experiments were carried out on tubular solar still in Allahabad climate conditions. Energy storage medium is used in still to produce distillate in the off sunshine hours.a correlation is developed for the productivity of a still using experimental results.the proposed correlation has been validated with the experimental results.the regression coefficient approaches to unity and the correlation may be perfect positive with least error.energy and exergy efficiency of a system were calculated.it is observed that productivity of solar still increase by 2% when energy storage medium is used. Keywords: Phase Change Material, Energy and Exergy efficiency, Correlation Coefficient. INTRODUCTION Although, more than two-thirds of the Earth surface is covered by water, many countries suffer for shortage of portable water is a serious issue that many countries suffer from. Furthermore, the worldwide rapid growth of industry and population has resulted in a large boom in demand for fresh water. The solar still is an ideal source of fresh water for drinking purpose. It is one of the most important and technically viable applications of solar energy. The production capacity of a simple type still is in the range of 2 5 l/m 2 /day [1]. This makes the system highly uneconomical. In solar desalination process, the productivity of the solar still is very less compared to other conventional desalination systems. Less productivity is the main drawback of solar still. For enhancing the productivity of solar still phase change material are used as energy storage system. Phase change material supply energy during off sunshine, particularly at night. Many researchers have investigated the effect of PCM on the productivity of solar still theoretically and experimentally [2-15]. Exergy analysis is based upon the second law of thermodynamics, which stipulates that all macroscopic process are irreversible.every such irreversible process entails a non recoverable loss of exergy Analysis of exergy losses identifies possibility of improving the design of system. Ranjan et. al. have performed exergy analysis of solar still and have found highest exergy destruction in the basin liner 42

2 [16] use of phase change material below the basin liner minimizing the exergy loss. In the present work stearic acid is used in the basin of tubular solar still to enhance the productivity of the still and to minimize the losses. EXPERIMENTAL SET UP A prototype solar still having a horizontal tray which acts as absorber of.77 m 2 was designed and constructed. Tray was constructed using galvanized iron sheet of thickness.5 mm and later on painted in black. The tray is surrounded by tubular structure made up of PVC sheet. The total area of the PVC cover is 3.52 m 2. The still is formed by a tubular transparent surface made up of PVC sheet. Testing was performed by placing the tubular solar still operating in sunlight for a 8 h period. The work has led to the development of the tubular 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 tubular solar still has shown that the productivity of the system was substantially increased in comparison with that of the basin type solar still. 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 set up are shown in figure1. Performance of Solar Still Figure 1: Photograph of Tubular Solar Still 1. The expression for overall thermal efficiency (η passive ) η passive = ( ) m= Productivity, L latent heat of vaporization, A w area, I(t) solar intensity 43

3 2. η ex = The exergy input to the solar still is radiation and can be written as Ex sun = Ex in =A w * I(t) *[ 1 - ( ) + ( )4 ] The exergy output of a solar still can be written as Ex evap = m L[ 1 - ( )] T a ambient temperature, T s sun temperature (6 K) RESULTS AND DISCUSSION Slar Intensity (w/m 2 ) Time of a day(hr) Fig.2: Variation of solar intensity with respect to time on a particular day in the month of March Fig. 2 shows the variation of solar intensity on a particular day of testing the tubular solar still in the month of March.The maximum intensity of 1 W/m 2 is received at 12: hrs. 2 wind speed(m/s) Time of a day (hr) Fig 3: Variation of wind speed with time on a particular day Fig.3 shows the variation of wind speed on a particular a day in the month of March.The maximum wind speed is 1.7 m/s at 2: hrs. 44

4 Temprature( c) Tw Tpcm Tb Tci Tco Ta Time of a day (hr) Fig.4: Variations of water temperature, PCM temperature, basin temperature, condensing cover and ambient temperature with respect to time on a particular day Fig.4 shows the variations of water temperature, PCM temperature, basin temperature, condensing cover and ambient temperature with time on a particular day. After sunshine, heat transfer takes place from basin water to PCM. Water temperature starts decreasing in after noon but water and PCM temperature equals at around 4 O clock. When water temperature decreases, PCM starts discharging heat to the water and nocturnal productivity increases. Relationship between basin water temperature and distillate output Productivity (ml) P= 5.498T w R² = Tepmpature ( o C ) Fig.5: Variation of productivity with water temperature During the experiments, the water temperature T w was varied between 35 C and 59 C. The following empirical relationships were obtained for mean hourly stationary productivity as function of water temperature. P = 5.489T w CONCLUSION Experiments were carried out on a tubular solar still integrated with stearic acid as energy storage material in Allahabad climatic condition. Some important conclusions were drawn: Daily energy efficiency of % is obtained. Instantaneous exergy efficiency varies between.5 and Daily exergy efficiency of.857 % is obtained. 45

5 An empirical relation for productivity P = 5.489T w is developed and the value of R 2 is equal to.84, shows good agreement with the experimental results. REFERENCES [1] V. Velmurugana, K. Srithar, Performance analysis of solar stills based on various factors affecting the productivity a review, Renew. Sustain. Energy Rev. 15 (211) [2] Ajeet Kumar Rai, Vivek Sachan and Maheep Kumar. (213, Experimental Investigation of a Double Slope Solar Still with a Latent Heat Storage Medium, International Journal of Mechanical Engineering and Technology: 4 (1) [3] H.E.S. Fath, Technical assessment of solar thermal energy storage technologies, Renewable Energy 14 (1998) [4] A.M. Radhawan, Transient performance of a stepped solar still with built-in latent heat thermal energy storage, Desalination 171 (24) [5] A.A. El-Sebaii, A.A. Al-Ghamdi, F.S. Al-Hazmi, A.S. Faidah, Thermal performance of a single basin solar still with PCM as a storage medium, Applied Energy 86 (29) [6] F.F. Tabrizi, M. Dashtban, H. Moghaddam, Experimental investigation of a weir type cascade solar still with built-in latent heat thermal energy storage system, Desalination 26 (21) [7] Al-Hamadani A.A.F. and Shukla S.K. (211), Modeling of solar distillation system with phase change material(pcm) storage medium, thermal science. [8] Hasan Falih M., Dr. Ajeet Kumar Rai, Vivek Sachan, Omar Mohammed (214). Experimental Study of Double Slope Solar Still with Energy Storage Medium, International Journal of Advanced Research in Engineering and Technology : 5(3) [9] Ankur Kumar Singh,Dr. Ajeet Kumar Rai, Vivek Sachan (214) Energy and Exergy Analysis of a Double Slope Solar Still International Journal of Mechanical Engineering and Technology :5(6) [1] Maheep Kumar, Ajeet Kumar Rai, Vivek Sachan (214), Experimental Investigation of a Solar Still Using Lauric Acid As A Energy Storage Medium, International Journal of Advanced Research in Engineering and Technology: 5(12), [11] Ajeet Kumar Rai,Vivek Sachan,Vinay Tripathi,Pramod kumar,abhishek Tripathi (214) Effect of Lowering Condensing Cover on the Performance of Solar Still, International Journal of Mechanical Engineering and Technology: 5(8) [12] Parmendra Singh, Dr. Ajeet Kumar Rai, Vivek Sachan (214) Study of Effect of Condensing Cover Materials on the Performance of a Solar, Still International Journal of Mechanical Engineering and Technology :5(5) [13] Ajeet Kumar Rai, Vivek Sachan and Bhawani Nandan. (213), Experimental study of evaporation in a Tubular solar still, International Journal of Mechanical Engineering and Technology: 4 (2) 1-9. [14] Ajeet Kumar Rai, Nirish Ningh, Vivek sachan (213)Experimental Study of a Single Basin Solar Still with Water Cooling of the Glass Cover, International Journal of Mechanical Engineering and Technology 4 (6) `1-7. [15] Ajeet Kumar Rai, Pratap singh, Vivek Sachan and Nirpendar bhaskar (213), Design,Fabrication and Testing of a modified single slop solar still, International Journal of Mechanical Engineering and Technology 4 (4) [16] K. R. Ranjan, S. C. Kaushik and N. L. Pawar Energy and exergy analysis of passive solar distillation systems, international journal of low carbon technologies