International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 627 635, Article ID: IJMET_08_07_070 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=7 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed THERMAL PERFORMANCE IMPROVEMENT OF FLAT PLATE SOLAR COLLECTOR USING NANO FLUIDS Malleboyena Mastanaiah Research Scholar, Department of Mechanical Engineering, JNTUA, Anantapuramu, A.P, India Prof. K. Hemachandra Reddy Professor, Department of Mechanical Engineering, JNTUCEA, Anantapuramu, A.P, India Dr. V. Krishna Reddy Professor, Department of Mechanical Engineering, KITS, Markapur, A.P, India ABSTRACT Extracting thermal energy from solar flat plate collectors is the simplest way than others. Collector performance depends upon the absorber material, radiation intensity, tracking system, working fluid characteristics etc. Properties of working substance plays a vital role that effects the collector efficiency and overall performance. An attempt has been made to utilize nano fluid as working substance in this work to increase the heat transfer from absorber to working fluid. These fluids contains metallic and non-metallic particles like CuO, Aluminum, aluminum oxides having higher thermal conductivity than water. The outlet temperatures, Thermal and collector efficiencies for different nano fluid flow rates against time and reduced temperature parameter were studied. Effect of nano particle Concentrations with base fluid was also examined and found increase in efficiency of the solar system to certain limit and supplementing the nano particles beyond the limit does not increase the efficiency. Key words: Nano fluid, Thermal conductivity, Copper oxide, Collector efficiency. Cite this Article: Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy. Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids. International Journal of Mechanical Engineering and Technology, 8(7), 2017, pp. 627 635. http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=7 http://www.iaeme.com/ijmet/index.asp 627 editor@iaeme.com
Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids 1. INTRODUCTION Many encouraging facts on solar energy, solar systems play a vital role in converting solar energy into heat or electrical energy. Solar thermal applications improved heat transfer techniques leads to better performance of the system. Among many possible heat transfer improvement techniques, usage of Nano fluids as working fluids is also an effective approach. Many works related to nano fluids usage in solar collector systems are in progress in the areas of water heaters, cooling systems, solar cells, solar stills, absorption refrigeration systems etc. Solar collectors in collecting thermal energy considered legendary based on the characteristics of heat transfer fluid and their construction Solar flat plate collectors are generally in water heating applications and the efficiencies are in the range of 65-70% which are very high than direct energy conversion systems having 15-17% efficiency. Nano fluid is the fluid with solid-liquid mix or suspensions formed by dissolving minute metallic or nonmetallic Nano particles in base fluids. Nano particles size (generally less than 100nm) gives them the ability to intermingle with base liquids at the molecular level. The metallic or nonmetallic Nano particles could cause the changes in heat transfer and transport properties of the base fluid. These fluids are the new generation heat transfer fluids for diversified applications in industrial and automotive industries as these are having excellent thermal performance. Higher thermal conductivity & radiative characteristics of Nano particles caused to be Nano fluids as promising working fluids in solar collector system [9]. 2. LITERATURE Y. Tian et al.[1] made a comprehensive review on different solar collectors and available thermal energy storage techniques. In their review they have considered different studies of collector design criteria and different materials which can store sensible, latent and chemical energies. Number of heat transfer enhancement possibilities are discussed by incorporating more thermal conductive materials and cascading techniques. Solar flat plate collector performance was analyzed by P.W.Ingle et al. [2] using CFD by simulating the collector with respect to different operating parameters. Unstructured grid using ICEM is adopted for better analysis. Small deviations are observed from simulated results to measured values and this may be due to the imperfectness during experimentation Titan C Paul et al[3] have utilized the advantage of usage of ionic liquids in solar thermal collectors and made several experiments to find the thermo physical properties of ionic liquids under different temperatures. The changes in ionic liquid properties such as viscosity, heat capacity, density and thermal conductivities are well studied and its suitability to use as working substances in solar applications. Several works on performance assessment of solar thermal collectors using Nano fluids as working fluids were reviewed by Navid Bozorgan et al [4].Comprehensive information on the usage of Nano fluids as the effective heat transfer fluids, was given by authors. Shailja Kandwal [5] worked on parabolic collector with nano fluid (water with Cuo) & Cuo-glycol based fluids and also with ethylene glycol and water. Efficiencies with all four fluids were compared under various concentrations & mass flow rates. Water with Cuo substance produces maximum efficiency among four working fluids and the results are also validated by CFD model results and found good agreement between two results. Different heat transfer fluids (HTFs) used in solar thermal applications was exploited by Umish Srivastva et al. [7]They made a review on the works used various HTFs for low, medium and high temperature applications. They concluded hydrocarbon oils be the promising fluid for majority high temperature applications among others and molten salts and metals are also have their significance in particular applications. Xie et al. [8] investigated on the alumina suspension thermal conductivity for different base fluids. Effect of thermal conductivity with volume fraction by both experimental and http://www.iaeme.com/ijmet/index.asp 628 editor@iaeme.com
Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy theoretical studies. Bharot vishal kumar G et al [6] exploited the usage of nano fluids as working fluid in solar parabolic tube collectors instead of water. They observed the exhibition of good thermal properties by both metallic and non-metallic nano materials and by using these substances, collector performance was improved. Authors worked with Copper oxide and Aluminium oxide and observed improvement in instantaneous efficiency of collector. This paper is aimed to study the improvement in heat transfer, collector efficiency by using CuO +water with different concentrations and flow rates on a solar flat plate collector. 3. METHODOLOGY Solar flat plate collector performance is estimate by using Nano fluid (Cu O+ Water) as working fluid with different concentrations of 0.01%, 0.05% and 0.1% for different flow rates 0.028, 0.036 and 0.045 Kg/sec. Solar collector outlet temperatures, thermal efficiency and instantaneous efficiencies are estimated and simulation studies are also done for the collector under same conditions. Tests were conducted for different solar intensities and obtained results from experiments and simulation studies are also compared. 4. RESULTS & DISCUSSIONS The results were noted by running the CuO + water as working fluid with different flow rates and different CuO concentrations on May 21 st of 2016 from morning 9:30 AM to 2:30 PM. The following graphs shows the thermal and instantaneous efficiencies under different conditions. The following figures 1, 2 and 3 illustrate the increase in working fluid temperature with solar flux and fluid flow rate. The test was conducted for the flow rates of 0.028, 0.036 and 0.045 kg/sec from morning 9:30 AM to 2:30 PM. It was observed that solar intensity increases up to afternoon 1:00 PM and decreases later on. In the morning the percentage of increase in solar intensity is more than in afternoon. The same conditions are simulated through CFD and found very good coincidence with smaller deviation percentages of the order 5-9%. Higher outlet temperatures were notice with simulation results than experimental one due to higher convection losses in actual conditions. The maximum amount of solar flux observed in figure 1, 2 and 3 was noticed to be 875.05, 886.27 and 862.97 W/m 2 respectively. Figure 4.1 Variation in solar intensity and temperature with time for Cuo-H2O based Nanofluid (0.01% concentration) at volume flow rate of 0.028 kg/sec Figure 4.2 Variation in solar intensity and temperature with time for Cuo-H2O based Nanofluid (0.01% concentration) at volume flow rate of 0.036 kg/sec http://www.iaeme.com/ijmet/index.asp 629 editor@iaeme.com
Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids Figure 4.3 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.01% concentration) at volume flow rate of 0.045 kg/sec Figure 4.4 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.05% concentration) at volume flow rate of 0.028 kg/sec The figures 4, 5 and 6 demonstrates the change of Nano fluid temperature with increase in flow rate and solar intensity. Experiments and simulations through CFD were done for the flow rates of 0.028, 0.036 and 0.045 kg/sec from morning 9:30 AM to 2:30PM for 0.05 % Nano fluid concentration. Similar trends were observed as in the previous case i.e. for 0.01 % concentration, solar intensity rises from 9:30 am to 12:30 pm and subsequently it goes on declining. It was observed that in the morning, the percentage of increase in solar intensity is more than in afternoon. Maximum temperatures obtained with increase in Nano particle concentration and the same was validated with simulated results. Fig. 5 & 6 shows the effect of flow rate for the same above conditions as in Fig.4 and observed the outlet temperature increase with increase in fluid flow rate. Simulated results also showed similar trends and higher values than experimental values of the order 5-9%, because of more convectional losses in experiments. Figure 4.5 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.05% concentration) at volume flow rate of 0.036 kg/sec Figure 4.6. Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.05% concentration) at volume flow rate of 0.045 kg/sec http://www.iaeme.com/ijmet/index.asp 630 editor@iaeme.com
Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy Figure 4.7 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.1% concentration) at volume flow rate of 0.028 kg/sec Figure 4.8 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid (0.1% concentration) at volume flow rate of 0.036 kg/sec The figures 4.7, 4.8 and 9 illustrate the increase in working fluid temperature with solar flux and fluid flow rate. The test was conducted for the flow rates of 0.028, 0.036 and 0.045 kg/sec from morning 9:30 AM to 2:30 PM. It was observed that solar intensity increases up to afternoon 1:00 PM and decreases later on. In the morning the percentage of increase in solar intensity is more than in afternoon. The same conditions are simulated through CFD and found very good coincidence with smaller deviation percentages of the order 6-10 %. Higher outlet temperatures were notice with simulation results than experimental one due to higher convection losses in actual conditions. Figure 4.9 Variation in solar intensity and temperature with time for Cuo-H 2O based Nanofluid Figure 4.10 Heat flux Vs Water outlet temperature at different flow rates http://www.iaeme.com/ijmet/index.asp 631 editor@iaeme.com
Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids Figure 4.11 Variation in thermal efficiency with (Ti-Ta)/I T for Cuo-H 2O based Nanofluid (0.01% concentration) at different volume flow rates for 30 0 collector tilt Figure 4.12 Variation in thermal efficiency with (Ti- Ta)/IT for Cuo-H2O based Nanofluid (0.05% concentration) at different volume flow rates for 30 0 collector tilt Highest temperatures for the flow rates of 0.028 kg/sec, 0.036 kg/sec and 0.045 kg/sec are observed as 345.2, 346.38 and 347.21K respectively. However slight increase in temperatures are observed with simulated results because of minimum losses are assumed in model than experimental results. The maximum amount of solar flux observed in above was noticed to be 864.16, 877.95 and 864.46 W/m 2 respectively. Results obtained from simulation studies with CFD are compared with experimental values and noticed both results are in good agreement as shown in fig 10. A slight higher values are observed with model run and it is because of higher convective and conduction losses with experiments. The below graph illustrates the both results for fluid inlet temperature of 302.99 K and for flow rates of 0.028 and 0.056 kg/sec. The Figures 11-13 illustrates the change in thermal efficiency with reduced temperature parameter i.e. (Ti-Ta)/IT at different fluid flow rates (0.028, 0.036 and 0.045 kg/sec). Highest thermal efficiency was noticed at the highest flow rate of 0.045 kg/sec because of maximum useful gain and minimum convection losses. The Fig 11 shows the variation in thermal efficiency with reduced temperature by taking nano fluid as working fluid (0.01% of CuO in base fluid water), for the same flow rate and other test conditions 0.01% of CuO +Water showing higher efficiency than water, it is because of higher thermal conductivity and specific heat of CuO that enhances the heat absorption hence thermal efficiency. The increase in maximum and minimum collecting efficiency with CuO +Water is 12.4% and 6.6% respectively. It is also observed that with increase in flow rate of nano fluids in tubes also increases the outlet temperatures of the fluid and thermal efficiency also increases. Thermal efficiency variation for 0.05% concentration of CuO+H2O also shows the similar trend as in 0.01% concentration that the efficiency of solar flat plate collector increases with mass flow rate and decreases with the increase in reduced temperature at any particular solar irradiation. The highest thermal efficiency at 0.05% concentration was 7.882, 7.982 and 8.08235 observed at 0.028, 0.036 and 0.045 kg/sec. With Nano particles size of 20 nm and mass flow rates of 0.028 to 0.045 kg/sec, highest efficiency was observed for 0.045 kg/sec and thermal efficiency increased with decrease in reduced temperature as shown in Fig 13. CuO concentration of 0.1% in base fluid shows maximum collector thermal efficiency when compared with the fluid concentrations of 0.05% and 0.01%. Fig. 14 shows with increasing concentration, thermal efficiency also increases and decreases with reduced temperature parameter. http://www.iaeme.com/ijmet/index.asp 632 editor@iaeme.com
Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy Figure 4.13 Variation in thermal efficiency with (Ti- Ta)/IT for Cuo-H2O based Nanofluid (0.1% conc) at different volume flow rates for 30 0 collector tilt Figure 4.14 Variation in Thermal efficiency with (Ti- Ta)/IT for CuO-H2O based Nanofluid for different concentrations at volume flow rate of 0.045 kg/sec Figure 4.15 Variation in instantaneous efficiency with time for Cuo-H2O based Nanofluid (0.01% concentration) at different volume flow rates Figure 4.16 Variation in instantaneous efficiency with time for Cuo-H2O based Nanofluid (0.05% concentration) at different volume flow rates Variation in instantaneous efficiency with time from morning 8:00 AM to 4:00 PM for different concentrations of Cuo-H2O based Nano fluid at different flow rates and were represented in figures 15 to 17. From Fig.15-17 shows the deviation of instantaneous efficiency for CuO + water at collector optimum inclination (38.13 0 ) and different mass flow rates. Results are drawn for optimum collector tilt as it shows maximum performance. From the above figures it was experienced that that at a flow rate of 0.045 kg/sec CuO gives highest instantaneous efficiency. Figure 4.17 Variation in instantaneous efficiency with time for Cuo-H2O based Nanofluid (0.1% concentration) at different volume flow rates Figure 4.18 Variation in instantaneous efficiency with time for Cuo-H2O based Nanofluid for different concentrations at volume flow rate of 0.045 kg/sec http://www.iaeme.com/ijmet/index.asp 633 editor@iaeme.com
Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids Highest performance is observed at 0.1 concentration of CuO Nano fluid. Instantaneous efficiency of the solar collector at 2:00PM for all the working fluid flow rates and even higher efficiencies are possible with higher dispersion Nano fluids. Simulation and Experiments proved that flat plate collector system performance increases with the usage of Nano fluids. Fig.18 shows with increasing concentration, Instantaneous efficiency also increases with time in a day from 8:00 AM to 2:00 PM and later on decreases. 5. CONCLUSIONS Many theoretical and experimental works shows the improvement in solar thermal energy collection system performance with the usage of Nano fluids as working fluids. This work was taken up with an objective of improving performance of solar collector system by using CuO-H2O based Nano fluids and experiments were carried out on solar flat plate collector. Experiments are carried out for different fluid flow rates and for different CuO concentrations in base fluid H2O. The obtained results are also confirmed with the simulation results of CFD software. From this work it was noticed that fluid outlet temperatures are continuously increases with time in a day and percentage of increase increases up to 2:00 PM and later on decreases. As the concentration of Nano particles increases the heat absorption capacity also increases hence fluid outlet temperature and system efficiency increases as Nano particles having higher thermal conductivity. However increase of particle concentration beyond certain limit does not increase the system efficiency. Highest temperatures for the flow rates of 0.028 kg/sec, 0.036 kg/sec and 0.045 kg/sec are observed as 345.2, 346.38 and 347.21K respectively. However slight increase in temperatures are observed with simulated results because of minimum losses are assumed in model than experimental results. REFERENCES [1] Y Tian, CY Zhao. A review of solar collectors and thermal energy storage in solar thermal applications Applied Energy 104 (2013) Pages 538 553. [2] P.W. Ingle, A.A. Pawar, B.D. Deshmukh and K.C. Bhosale (2013) CFD analysis of solar flat plate collector International Journal of Emerging Technology and Advanced Engineering, Volume 3, Issue 4, April 2013, Pages 337-342, ISSN: 2250-459. [3] Titan C. Paul et al. Thermal performance of ionic liquids for solar thermal applications Experimental Thermal and Fluid Science 59 (2014), Pages 88 95, 0894-1777 [4] Navid Bozorgan and Maryam Shafahi, Performance evaluation of Nano fluids in solar energy: a review of the recent literature Micro and Nano Systems Letters a springer open journal (2015) 3:5, Pages 1-15 [5] Shailja Kandwal, An experimental investigation into Nano fluids based parabolic solar collector Master s thesis (2015), Department of mechanical engineering, Thapar University, Patiyala. [6] Barot Vishalkumar G and K.D Panchal, Nano fluid : A Tool to Increase the Efficiency of Solar Collector International Journal of Innovations in Engineering and Technology, Volume 5, Issue 2, April 2015, Pages 350-355, ISSN: 2319-1058 [7] Umish Srivastva1 et al. Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications Fundamentals of Renewable Energy and Applications, 2015, 5:6 http://www.iaeme.com/ijmet/index.asp 634 editor@iaeme.com
Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy [8] Xie. H., Wang. J., Xi. T., Liu. Y., Ai. F. and Wu, Q. (2002). Thermal conductivity enhancement of suspensions containing Nano sized alumina particles Journal of applied physics.91:4568-72. [9] Mohsen Sheikholeslami Davood Domairry Ganji, A book on Applications of Nano fluid for Heat Transfer Enhancement,, ISBN: 9780081021729, March 2017 [10] Sandeep Kumar and Satbir Singh Sehgal. Experimental Performance Analysis on Flat Bed Solar Collector with and without Microchannel Fins. International Journal of Mechanical Engineering and Technology, 8(6), 2017, pp. 740 749. http://www.iaeme.com/ijmet/index.asp 635 editor@iaeme.com