Performance enhancement of a renewable thermal energy collector using metallic oxide nanofluids
2017; Institution of Engineering and Technology; Volume: 13; Issue: 2 Linguagem: Inglês
10.1049/mnl.2017.0410
ISSN1750-0443
AutoresT.V.R. Sekhar, Ravi Prakash, Gopal Nandan, Marisamy Muthuraman,
Tópico(s)Solar-Powered Water Purification Methods
ResumoMicro & Nano LettersVolume 13, Issue 2 p. 248-251 ArticleFree Access Performance enhancement of a renewable thermal energy collector using metallic oxide nanofluids Talluri Venkata Raja Sekhar, Corresponding Author Talluri Venkata Raja Sekhar tvrsekhar1974@gmail.com Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorRavi Prakash, Ravi Prakash Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorGopal Nandan, Gopal Nandan Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorMarisamy Muthuraman, Marisamy Muthuraman Project Engineering, Boiler & Auxiliaries, NTPC Limited, Uttar Pradesh, Noida, 201301 IndiaSearch for more papers by this author Talluri Venkata Raja Sekhar, Corresponding Author Talluri Venkata Raja Sekhar tvrsekhar1974@gmail.com Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorRavi Prakash, Ravi Prakash Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorGopal Nandan, Gopal Nandan Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida, 201303 IndiaSearch for more papers by this authorMarisamy Muthuraman, Marisamy Muthuraman Project Engineering, Boiler & Auxiliaries, NTPC Limited, Uttar Pradesh, Noida, 201301 IndiaSearch for more papers by this author First published: 01 February 2018 https://doi.org/10.1049/mnl.2017.0410Citations: 21AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract A renewable thermal energy collection device was built and metallic oxide nanofluids namely cerium oxide, aluminium oxide and titanium oxide in base fluid water were used. At 3 vol% and a flow of four litres per minute, the renewable energy collector efficiency was computed and compared with the values obtained using water as the working fluid. It was observed that by using Ceria, Alumina and Titania nanofluids, collector efficiencies of 60%, 58% and 56% were achieved respectively. When compared with the values obtained by using water, the efficiency enhancement was 27% for Ceria, 25% for Alumina and 23% for Titania nanofluids. Nomenclature Ac area of collector in m2 Cp,nf specific heat of nanofluid in kJ/kg °C E incident energy in J I intensity of solar flux in W/m2 mnf mass of nanofluid in g Q total quantity of heat supplied in J t2 final temperature of the fluid in °C t1 initial temperature of the fluid in °C t time of the experiment in seconds Tnf in collector inlet temperature of the fluid in °C Tnf out collector outlet temperature of the fluid in °C η focusing efficiency of the collector Ф volume fraction of nanoparticles in % 1 Introduction The addition of dispersed particles brings about a change in the specific heat of the working fluid and affects the heat transfer coefficient of the working fluid. The concept of nano-sized particles introduced by Choi in 1978 helped in the improvement of the thermal conductivity of the base fluid in which these nm-sized particles were dispersed without apparent problems of settlement or chocking of the loop circuit. Kasaeian et al. [[1]] evaluated the performance of a solar parabolic trough collector (PTC) using Carbon Nano Tubes (CNTs)/oil nanofluid with a non-evacuated and an evacuated copper tube. It was shown that with an evacuated copper tube 11% higher efficiency of the collector was attained. Khullar et al. [[2]] dispersed aluminium nanoparticles in Therminol VP-1 base fluid and the nanofluid showed around 10% enhancement in the efficiency. Tayade et al. [[3]] evaluated the performance of solar PTC. The receiver outlet temperature is plotted versus time and it is observed that peak temperature of 62°C is attained at 1300 h in the day time. Ghasemi et al. [[4]] used cuprous oxide water nanofluid in PTC. Numerical analysis involving parameters such as fluid velocity, volume concentration, concentration ratio and receiver length was performed. As volume concentration of the nanoparticles increased, the efficiency increased. As the length of receiver increased, the mean temperature increased. However, convective losses increased which steeply decreased the thermal efficiency. With the increase of fluid velocity, convective losses decreased which led to decrease in the mean outlet temperature. However, in this case, the thermal efficiency increased. Investigation with transparent receiver tubes was performed by Khullar et al. [[5]]. The optical efficiency of the collector as a function of receiver tube radius and nanoparticle concentration is computed with alumina nanoparticles in different base fluids like ethylene glycol, propylene glycol and Therminol VP1 in a parabolic solar collector. It is found that among base fluids, water has the highest solar energy capturing capacity. Gas phase nanofluids were studied with simulations on a transparent PTC with a transparent receiver tube by De Risi et al. [[6]]. A gas phase mixture of cuprous oxide and nickel was used with a volume concentration of 0.3%. The outlet temperature of 650°C was attained and the thermal efficiency of 62.5% was achieved. Mwesigye et al. [[7]] dispersed alumina nanoparticles in synthetic oil Syltherm 800 at 8% volume concentration. The collector efficiency increased by 7.6%. Bellos et al. [[8]] used thermal oil, thermal oil with nanoparticles and pressurised water in a high temperature PTC. In addition to the use of nanofluids, geometrical modifications were performed which improved the thermal efficiency by 9%. An evacuated solar air collector was integrated with a compound parabolic collector by Liu et al. [[9]] and used cuprous oxide nanofluid to achieve an increase in efficiency up to 6.6%. Copper Therminol VP1 nanofluid was used by Mwesigye et al. [[10]] in a high concentration ratio parabolic trough solar collector. At a volume fraction of 6%, there is an increase of 12.5% in the thermal efficiency of the collector. Wang et al. [[11]] employed alumina-synthetic nanofluid. With varying heat transfer fluid, inlet velocities have a considerable impact on the temperature distribution and collector performance. As the inlet velocity increases there is a jump in the thermal efficiency when oil is used as a working fluid. When nanofluid is used higher efficiency is attained which do not change significantly with the increase of inlet velocity. Xu et al. [[12]] conducted a comparison of the performance of a nanofluid-based direct absorption-based solar collector with a nanofluid-based PTC. The PTC exhibited higher thermal efficiency in a fixed temperature range of 60–160°C. Kaloudis et al. [[13]] tested a parabolic trough solar collector with alumina nanofluid and yielded enhanced heat transfer results. The base fluid used was Syltherm 800 fluid and at a nanoparticle concentration of 4%, the collector efficiency showed an improvement of 10% in relation to efficiency obtained with water as the working fluid. Basbous et al. [[14]] used alumina nanoparticles in a base of Syltherm 800 base fluid to test the efficiency of the solar PTC. Results showed that the convection coefficient between the receiver and the heat transfer fluid improved by 18% and the heat losses decreased by 10% with the temperature rise of the fluid. This implied an improvement of collector thermal efficiency with the use of nanofluids in the parabolic collector. Furthermore, at a flux of 940 W/m2, the maximum mean temperature of the working fluid was obtained as 400°C, which is highly desirable for industrial applications. A review conducted by Taylor et al. [[15]] suggested that when nanofluid receivers were used in concentrating devices with concentration ratios in the range of 100–1000, efficiency enhancements of up to 10% were obtained. Sabiha et al. [[16]] used Single-Walled Carbon Nano Tubes (SWCNT) water nanofluid in the solar collector and efficiency enhancement by 93% at 0.2 vol% was obtained. When alumina and ferric nanofluids were employed by Abid et al. [[17]] in PTCs in place of molten salts, the exergy and energy efficiency was found to enhance by around 5%. Investigations comparing different metallic oxide nanoparticles with regard to thermal performance enhancement in PTCs are limited in the previous literature and since parabolic trough concentrating collectors are gaining relevance due to their robust design, a long life and higher collector efficiency, the present study is conducted to investigate the thermal enhancements by using metallic oxide nanofluids in a PTC set up built for the experimental study. 2 Samples preparation The preparation of homogenous and stable samples is the key to the accuracy of the obtained experimental results. The nanofluids are procured from the reputed supplier M/s Alfa Aesar Pvt. Ltd having a purity of 99% as per the Material Specification Data Sheet (MSDS). 1000 ml of cerium oxide, aluminium oxide and titanium oxide nanofluid is procured. To obtain significant results, six samples are prepared for each nanofluid viz. 3, 2, 1.5, 1, 0.75 and 0.5 vol%. The nanofluid procured is 1000 ml by volume and having a volume concentration of 10–12 vol% as per the supplier MSDS. To prepare the homogeneous solution, the solution is continuously stirred with a magnetic stirrer for 1 h as shown in Fig. 1. Subsequently, the nanofluid was transferred into an ultrasonicator. The sonication is carried out for 4 h at a frequency of 40 kHz and the contents are transferred to a transparent glass jar to check any settlement. Afterwards, it is ensured that the nanofluid was stable, the same was transferred into a metered tank and 1000 ml nanofluid was diluted with distilled water of 3000 ml to attain a nanofluid solution of 4000 ml with a volume fraction of 3%. Fig. 1Open in figure viewerPowerPoint Magnetic stirring of titania-water nanofluid By continuous agitation, the solution is used for experimentation purposes. After the tests were conducted at 3 vol%, the solution was further diluted in steps to achieve other volume fractions and tests were carried out for the samples shown in Fig. 2. Fig. 2Open in figure viewerPowerPoint Samples of nanofluids prepared 3 Experimental set-up for study The prepared nanofluid as per the required volume fraction is circulated using a fluid pump as shown in the scheme in Fig. 3. The incident solar flux is concentrated with the help of the parabolic mirror onto the copper absorber tube and the circulating fluid collects the heat and gets heated up in the built collector model (Table 1) as shown in Fig. 4. The incident solar flux is measured with the help of a digital solar power meter collector (TENMARS make) and the thermal energy gained by the nanofluid is computed by the temperature rise. The fluid temperature readings for a fixed interval of 60 min is recorded and tabulated using different volume fractions of the nanofluid. Fig. 3Open in figure viewerPowerPoint Solar thermal energy collector scheme diagram Fig. 4Open in figure viewerPowerPoint Parabolic collector built model Table 1. Solar collector specifications Sl no. Equipment Dimensions 1 parabolic trough 2.5 m2 2 incident angle 25° 3 absorber tube copper 20 mm diameter 4 flow type assisted, 0–8 lpm 5 concentration ratio 60 The proposed scheme consists of assisted circulation of the fluid with the help of a low power nanofluid pump operating within a pressure range of 1–2 KSC (kg per cm2). The fluid pump achieves sufficient flow in the range of 0–8 lpm (litres per minute). The nanofluid pump flow is regulated at 4 lpm flow rate with the help of regulation valve. The fluid inlet is represented by thin lines and the outlet fluid which is warmer is represented by bold lines in the scheme. The nanofluid loop is a 20 mm diameter heat insulated PVC pipe and the heated fluid is returned to the nanofluid tank. The built experimental set up as shown in Fig. 4 consists of a metered nanofluid tank placed at the bottom of the collector set up. A nanofluid pump continuously circulates the nanofluid in the closed loop circuit and passes through the copper absorber tube which is placed in the focal plane of the solar collector. The control panel of the built collector model as shown in Fig. 5 consists of a solar power meter, inlet and outlet pressure gauges and three numbers of digital temperature gauges to measure the inlet and outlet fluid temperature within an accuracy of 0.1°C. The fluid flow is measured in lpm with the help of a rotameter placed in the loop. Fig. 5Open in figure viewerPowerPoint Control panel of the built model 4 Thermal efficiency using nanofluid As shown in Fig. 2, the solution of metallic oxide nanofluid and distilled water is prepared for six different volume fractions 3, 2, 1.5, 1.0, 0.75 and 0.50 vol%, respectively. For different volume fractions of cerium, alumina and titania nanofluids, and at an incident flux of 860 W/m2, an ambient temperature range of 25–30°C, experimentation at a flow rate of 4 lpm using the built collector model is carried out. It is observed from Tables 2–4 that, as the nanofluid is diluted, it is more sensitive to the incident flux and the outlet temperature to the inlet temperature difference increases. Table 2. Ceria nanofluid at various volume fractions Ceria nanofluid inlet outlet temperatures ϕ, % mnf, lpm Tnf,in, °C Tnf,out, °C 3 4 30 44.8 2 4 30 45.1 1.5 4 30 45.3 1 4 30 45.4 0.75 4 25 43.1 0.5 4 30 45.2 Table 3. Alumina nanofluid at various volume fractions Alumina nanofluid inlet/outlet temperatures ϕ, % mnf, lpm Tnf,in, °C Tnf,out, °C 3 4 30 44.7 2 4 30 44.9 1.5 4 30 45 1 4 30 45.1 0.75 4 25 42.1 0.5 4 30 44.5 Table 4. Titania nanofluid at various volume fractions Titania nanofluid inlet/outlet temperatures φ, % mnf, lpm Tnf,in, °C Tnf,out, °C 3 4 30 44.4 2 4 30 44.8 1.5 4 30 44.9 1 4 30 45 0.75 4 30 45.1 0.5 4 30 44.5 The mass of the nanofluid is calculated by multiplying the density of nanofluid with the volume of the nanofluid circulated in a time interval of 1 h. Using the standard reference values of specific heat of distilled water at 60°C, the specific heat of the nanofluid at different volume fractions is computed and with the help of (1) the total heat gained by the nanofluid in 1 h interval is calculated. (1) 5 Results and discussion With the help of a solar power meter, incident flux on the collector is determined and the concentrated flux on the absorber tube is determined. It is found that focusing efficiency of the built collector is around 10%. By using these values and substituting in (2), the total incident energy as an input to the collector is calculated. The time for the study is a fixed interval of 1 h (2) Collector efficiency values obtained in the study as the ratio of (1) and (2) are graphically represented for each volume fraction of the nanofluid as shown in Fig. 6. Fig. 6Open in figure viewerPowerPoint Enhancement of collector efficiency using nanofluid 6 Conclusion In the present study, six samples of cerium oxide, aluminium oxide and titanium oxide nanofluids of different volume fractions are prepared and subjected to experimental set up have shown that there is an enhancement of thermal efficiency of the built parabolic collector. At a volume fraction of 3%, the enhancements of 27, 25 and 23% were obtained by using ceria nanofluid, alumina titania nanofluid, when compared with using water as the working fluid. The collector can be integrated with renewable power generation systems for achieving high efficiency systems. 7 Acknowledgements The authors would like to acknowledge the support of Department of Mechanical and Automation Engineering, Amity University, Uttar Pradesh, Noida for the support extended during the testing of the experimental set up. 8 References [1]Kasaeian A. Davirana S. Azarian R.D. et al.: 'Performance evaluation using nanofluid and capability study of a solar parabolic trough collector', Energy Convers. Manage., 2015, 89, pp. 368– 375 (doi: 10.1016/j.enconman.2014.09.056) [2]Khullar V. Tyagi H. Phelan P.E. et al.: 'Solar energy harvesting by using nanofluids based concentrating solar collector'. ASME 2012 Third Int. Conf. on Micro/Nanoscale Heat and Mass Transfer, 2012, pp. 259– 267 [3]Tayade M.G. Thombre R.E. Dutt S.: 'Performance evaluation of solar parabolic trough', Int. J. Sci. Res. Publ., 2015, 5, (1), pp. 1– 5 [4]Ghasemi S.E. 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