AN EXPERIMENTAL INVESTIGATION OF SINGLE SLOPED BASIN TYPE SPHERICAL FLOATING JUTE CLOTH ABSORBERS SOLAR STILL

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 6, June 218, pp , Article ID: IJMET_9_6_15 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed AN EXPERIMENTAL INVESTIGATION OF SINGLE SLOPED BASIN TYPE SPHERICAL FLOATING JUTE CLOTH ABSORBERS SOLAR STILL Abhay Agrawal Assistant Professor, Department of Mechanical Engineering, Rewa Engineering College, Rewa, MP, India R.S. Rana Department of Mechanical Engineering, Maulana Azad National Institute of Technology, Bhopal, MP, India ABSTRACT In this work, an experimental study was conducted in Rewa, India for improving the performance of single sloped basin type solar still. For this purpose, multiple spherical floating jute cloth absorbers are floated over the surface of basin water of still. Due to low thermal capacity and capillary property of porous absorbers, a high rate of evaporation of water was obtained, resulting in more productivity. The effect of solar radiation, ambient temperature, absorber temperature, glass cover temperature, basin water temperature, hourly and daily distillate output and daily efficiency of modified and conventional stills were studied. It is observed that the modified solar still gives 46.33% higher distillate output over the conventional still. The daily efficiency of modified still was 55.73%, which is higher than that of the conventional still. Key words: Solar Still, Spherical floating absorber, Jute Cloth, Distillate Output, Daily efficiency Cite this Article: Abhay Agrawal and R.S. Rana, An Experimental Investigation of Single Sloped Basin Type Spherical Floating Jute Cloth Absorbers Solar Still, International Journal of Mechanical Engineering and Technology 9(6), 218, pp INTRODUCTION Along with healthy food and clean air, potable water is also a fundamental requirement of humankind. But due to increase in population and industrialization, the scarcity of drinking water is increasing day by day as a significant problem. Even though water surrounds more than two-thirds of our land, all this water is very saline. If it is possible to convert this water into pure water, then we can solve this problem. Available water purification techniques like editor@iaeme.com

2 An Experimental Investigation of Single Sloped Basin Type Spherical Floating Jute Cloth Absorbers Solar Still reverse osmosis, electrodialysis, vapor compression, multistage flash distillation, multiple effect distillation, etc., are costly and more energy consuming. Solar distillation is one of the low-cost water purification technology operated by solar energy which is freely available. Therefore, it is beneficial in rural and remote areas of our country where impure water is available, but electricity is not available. In solar distillation process, a solar still is used, which is simple to fabricate by the locally available material. The main limitation of solar still is to produce the least amount of distillate output as compared to other modern water purification techniques. Several researchers have conducted the theoretical and experimental works and suggested many modifications to improve the productivity of conventional type solar still. Dunkle [1] presented the empirical formulas for calculation of heat transfer coefficients for rooftop solar still. A thermal model was developed by Kumar and Tiwari [2] for the coefficient of convective mass transfer for various values of Grashof Number. Lof et al. [3] observed the effect of various climatic parameters on the yield of the solar still. Cooper [4,5] developed a simulation technique to analyze the impact of different parameters of the solar still and estimated the maximum efficiency of solar stills. Garg and Mann [6] investigated the performance of solar stills (single and double slope) for different parameters in Indian arid zone conditions. Sebaii et al. [7] developed a mathematical model for analyzing the effect of phase change material (PCM) placed below the basin liner in single slope basin type solar still. It was found that the productivity increased to 9.5 Kg/m 2 /day with the average daily efficiency of about 85.3% which are higher than those for conventional solar still. Khaled and Eldalil [8] obtained an improvement in performance of conventional solar still by using vibratory harmonic effect. The productivity due to vibration was increased to 5.8l /m 2 /day with the average daily efficiency of about 6%, whereas the nocturnal production ranged from 38% to 57%. An experimental study was conducted by Sakthivel et al. [9] on the regenerative solar still using jute cloth and found an improvement in yield of 2% and efficiency increased by 8%. Srivastava and Agrawal [1] conducted an experimental and theoretical analysis of single basin type solar still with multiple floating porous absorbers under the Indian climatic conditions. They observed that the distillate output of modified still was increased by about 68% on clear days and about 35% on cloudy days as compared to conventional still. Agrawal et al. [11] presented theoretical, and the experimental study of single sloped basin type solar still for five different basin water depths (2 cm to 1 cm). They found that the daily distillate output (theoretical and experimental) for 2 cm basin water depth was approximately 5.37 kg/m 2 /d and 4.26 kg/m 2 /d respectively. For 1 cm basin water depth, the theoretical and experimental value of the distillate output were approximately 4.17 kg/m 2 /d and 3.24 kg/m 2 /d respectively. Dubey and Rai [12] improved the performance of conventional solar still by using the double condensing chamber. It was observed that the productivity and the daily exergy efficiency of still with the separate condenser were increased by 36.9% and 6.8% respectively as compared to those for conventional still. An experiment was conducted by Bhaskar and Rai [13] to compare the productivity of tubular solar still with and without fan. They observed that the productivity of tubular solar still with fan is 48.33% higher than that of the still without fan. In the present work, a single slope basin type spherical floating jute cloth absorbers solar still is designed. The objectives of this work are as follows: To modify the design of conventional solar still for improving the performance editor@iaeme.com

3 Abhay Agrawal and R.S. Rana To measure the operational parameters of modified solar still namely spherical absorber temperature, glass temperature, basin water temperature, basin liner temperature and distillate output. To improve the performance of conventional solar still by introducing spherical floating jute cloth absorbers in the basin. 2. EXPERIMENTAL SETUP AND PROCEDURE An experimental study was conducted in outdoor conditions of Rewa, Madhya Pradesh, India (24 33' N, 81 18' E). Schematic diagram and a photograph of single sloped basin type spherical floating jute cloth absorbers solar still are presented in Fig. 1 and 2 respectively. In this setup two single sloped basin type solar stills of similar size were designed and fabricated by the plywood (.9 m thick). Metallic basin boxes were placed in the plywood frame with proper insulating material layers. Each basin box was made by G.I. sheet (.1 m thick) and has an effective area of.41 m 2. It was coated with dull black paint to enhance the absorption of solar radiation. One of the two stills was modified by using the multiple number of spherical floating black jute cloth absorbers, which were prepared by wrapping the black jute cloth completely around the spherical hollow plastic ball of.65 m diameter. Due to the capillary property of jute cloth, water is lifted through jute fiber so that cloth remains wet during the experiment. In the modified still, a total number of 18 spherical absorbers were used to cover the complete area of basin water surface. Both stills were covered by glass cover (.4 m thick) at an angle of 24 with the horizontal. Rubber gaskets were used on the edges of glass cover to prevent the leakage of water vapor from the stills. The water tank was connected with solar stills for supplying the water in order to maintain the basin water level A condensate channel was attached at the lower side of both the stills to collect the condensate. The graduated bottles were used to collect and measure the distillate output. Values of solar intensity, wind speed, and ambient temperature were recorded from the solar station at the Rewa Engineering College, Rewa India. The temperature was measured at various positions of the setup, namely spherical absorber, basin water surface and glass cover with the help of copper-constantan thermocouples connected to a dual channel digital temperature indicator. Figure 1 Schematic diagram of modified solar still editor@iaeme.com

4 An Experimental Investigation of Single Sloped Basin Type Spherical Floating Jute Cloth Absorbers Solar Still Glass cover Insulating foam Blackened jute cloth Distillate Channel Thermocouple wires Spherical floating absorber Measuring Bottle Digital thermometer Figure 2 Photograph of experimental setup of modified solar still The experimental setup is kept in the North-South direction to receive maximum solar radiation throughout the year. The impure water (TDS value 89 mg/ml) is supplied to the basin of both stills to maintain the basin water depth of 2 cm during the experimentation. The reading of solar intensity, absorber temperature, basin water temperature, glass temperature, ambient temperature, distillate output and wind speed of both the solar stills were recorded from 8. a.m. to 8. p.m. on an hourly basis and then one measurement at 8 a.m. on the next day, thereby covering 24 hours duration. The experiment was performed for one day (16/6/217) during the summer season. 3. DAILY PRODUCTIVITY AND DAILY EFFICIENCY OF MODIFIED SOLAR STILL The daily productivity of modified solar still can be obtained as, (3.1) Here, M wsa Hourly distillate output per unit basin area of modified still M' wsa Daily distillate output per unit basin area of modified still The daily efficiency of modified solar still is given by the relation, ( ) Here, I(t) Solar Intensity (W/m 2 ) L e Latent heat of vaporization of water (245 J/kg) Efficiency of solar still η osa (3.2) editor@iaeme.com

5 Temperature ( C) Solar radiation (w/m 2 ) Ambient Temperature ( C) Abhay Agrawal and R.S. Rana 4. RESULTS AND DISCUSSION Fig. 3 shows the Variation of solar radiation and ambient temperature with respect to time on an hourly basis. Since both the solar stills were kept on the same platform and their orientations were same. Hence the solar intensity received was also the same. The intensity of solar radiation continuously increased and reached its maximum value at mid-noon, then gradually decreased till the evening. The maximum value of solar radiation was obtained as 943 W/m 2 (mid noon) on 16 June 217, whereas the maximum value of ambient air temperature was C at 1 p.m. Hourly variation of spherical floating absorber surface temperature, basin water temperature and glass cover temperatures of both the stills are shown in Fig. 4. Floating absorber temperature of modified still was quickly raised from 8 a.m. to 3 p.m. as compared to conventional still due to its low thermal inertia property. Glass cover temperature of modified still attained the maximum value of 66.1 C at 1 p.m., while in conventional still, maximum glass cover temperature was 61.5 C at 2 p.m Figure 3 Variation of solar radiation and ambient temperature with time Solar radiation 16/6/17 Ambient Temp. 16/6/ Spherical floating absorber surface temperature of modified still Basin water temperature of conventional still Glass cover temperature of modified still Glass cover temperature of conventional still Figure 4 Comparison of various temperatures of the modified and conventional still Fig. 5 shows the variation of evaporative heat transfer coefficients for modified and conventional stills with time. The evaporative heat transfer coefficient at each hour was calculated by the Dunkle s relation [1]. Larger the value of evaporative heat transfer coefficient, greater the value of distillate output. It has been observed that the value of evaporative heat transfer coefficient for modified still was higher than that for the conventional still during high solar intensity hours. The maximum values of evaporative heat editor@iaeme.com

6 Distillate (Kg/m 2 ) Evap. heat transfer coff. (W/m 2 C) An Experimental Investigation of Single Sloped Basin Type Spherical Floating Jute Cloth Absorbers Solar Still transfer coefficients for modified and conventional stills were W/m2 C (at 1 p.m.) and W/m2 C (at 2 p.m.) respectively. The variation of distillate output of modified and conventional stills with time is shown in Fig. 6. It has been noticed that the modified still gives higher distillate output in each hour (8 a.m. to 4 p.m.) in comparison to the conventional still. This is due to the low thermal capacity of spherical floating absorbers. Besides that spherical absorbers cover the whole basin water surface, thereby maximum solar radiation was absorbed by the floating absorbers and very less amount transferred to the basin liner and bottom of the solar still resulting in minimizing the base heat losses. The figure indicates that the maximum distillate output for modified and conventional still was obtained as.954 Kg/m 2 /h (at 1 p.m.) and.7 Kg/m 2 /h (at 2 p.m.) respectively Modified still Conventional still Figure 5 Variation of evaporative heat transfer coefficient with time for modified and conventional still Hourly distillate output of spherical floating absorber modified still Hourly distillate output of conventional still Figure 6 Variation of distillate with time for modified and conventional still In Fig. 7, the variation of cumulative distillate output with time is shown in modified and conventional stills. It has been observed that the daily distillate output of modified still was higher than that for the conventional still by 46.33%. The daily distillate outputs of modified and conventional solar stills were 6.29 Kg/m 2 /day and Kg/m 2 /day respectively editor@iaeme.com

7 Daily efficiency (%) Distillate output (Kg/m 2 ) Cumulative distillate output (Kg/m 2 ) Abhay Agrawal and R.S. Rana Spherical floating absorber modified still Conventional still Figure 7 Variation of cumulative distillate output with time for modified and conventional still Modified still Convenntional still Day distillate output Night distillate output Daily distillate output Figure 8 Comparison of day, night and daily distillate output of modified and conventional still Fig. 8 depicts the comparison of day, night and daily distillate output of modified and conventional stills. The values of distillate output of modified and conventional still for daytime (8: a.m. to 7: p.m.) were Kg/m 2, and 4.15 Kg/m 2 respectively and for night (8: p.m. to 7: a.m.) were.82 Kg/m 2, and.93 Kg/m 2 respectively Modified still Conventional still Daily efficiency (%) Figure 9 Daily efficiency of modified and conventional still editor@iaeme.com

8 An Experimental Investigation of Single Sloped Basin Type Spherical Floating Jute Cloth Absorbers Solar Still In Fig. 9 shows the daily efficiency of modified and conventional stills. It can be observed that the daily efficiency of modified still is higher than that of conventional still. The values of daily efficiency for modified and conventional stills are 55.73% and 38.8% respectively. 5. CONCLUSIONS In this work, experiments were conducted on spherical floating jute cloth absorbers modified still and conventional still in outdoor conditions of Rewa, M.P., India. The following conclusions have been drawn. 1. It was observed that the spherical floating absorbers were heated quickly as compared to basin water of conventional still due to its low thermal capacity. Because of this, higher distillate output was obtained in modified still. 2. Spherical absorber temperature was always higher than that of basin water of still. 3. The value of evaporative heat transfer coefficient for modified still was higher than that of conventional still. 4. The distillate output of modified still was 46.33% higher than that of conventional still. 5. The values of daily distillate output for modified and conventional stills were 6.29 Kg/m 2 /day and Kg/m 2 /day respectively. 6. The daily efficiency (55.73%) of modified still was higher as compared to the daily efficiency (38.8%) of conventional still. 7. Due to higher efficiency and low material cost of modified still, it is more suitable for remote, rural and arid areas of India. ACKNOWLEDGEMENTS We are very thankful to Maulana Azad National Institute of Technology Bhopal, and Rewa Engineering College Rewa, M.P. India for providing facilities and continuous support and guidance to complete this research work. REFERENCES [1] R.V. Dunkle, Solar water distillation the roof type still and multiple effect diffusion still: International Developments in Heat Transfer, ASME, Proceedings of International Heat Transfer Conference, University of Colorado, 1961, [2] S. Kumar, G.N. Tiwari, Estimation of convective mass transfer in solar distillation system, Solar Energy, 57, 1996, [3] G.O.G. Lof, J.A. Eibling, J.W. Bloemer, Energy balances in solar distillation, AICHE J., 7 (4), 1967, [4] P.I. Cooper, The maximum efficiency of single effect solar still, Solar Energy, 15, 1973, [5] P.I. Cooper, Digital simulation of transient solar still processes, Solar Energy, 12, 1969, 313. [6] H.P. Garg, H.S. Mann, Effect of climatic, operational and design parameters on the year round performance of single-sloped and double-sloped solar still under Indian arid zone conditions, Solar Energy, 18, 1976, [7] A.A. Sebaii, A.A. Al-Ghamdi, F.S. Al-Hazmi, Adel S. Faidah, Thermal performance of a single basin solar still with PCM as storage medium, Appl. Energy, 86, 29, editor@iaeme.com

9 Abhay Agrawal and R.S. Rana [8] M.S. Khaled, Eldalil, Improving the performance of solar still using vibratory harmonic effect, Desalination, 251, 21, [9] M. Sakthivel, S. Shanmugasundaram, T. Alwarsamy, An experimental study on a regenerative solar still with energy storage medium jute cloth, Desalination, 264, 21, [1] Pankaj K. Srivastava, S. K. Agrawal, Experimental and theoretical analysis of single sloped basin type solar still consisting of multiple low thermal inertia floating porous absorbers, Desalination. 311, 213, [11] Abhay Agrawal, R.S. Rana, Pankaj K. Srivastava, Heat transfer coefficients and productivity of a single slope single basin solar still in Indian climatic condition: Experimental and theoretical comparison, Resource-Efficient Technologies, 3, 217, [12] Richa Dubey, Ajeet Kumar Rai, Comparative performance of a double condensing chamber solar still with a conventional solar still, International Journal of Mechanical Engineering and Technology (IJMET), Volume 8, Issue 11, November 217, [13] Nripendra Bhaskar, Ajeet Kumar Rai, Thermal investigation of a tubular solar still, International Journal of Mechanical Engineering and Technology (IJMET), Volume 9, Issue 1, January 218, editor@iaeme.com