Subramani, J.
Nagarajan, P. K.
Mahian, Omid
Sathyamurthy, Ravishankar
The efficiency of a parabolic trough solar collector (PTSC) was enhanced by using TiO2/DI-H2O (De Ionized water) nanofluid. Test samples consisting of nanofluids with concentrations of 0.05%, 0.1%, 0.2%, and 0.5% were compared with deionized water (the base fluid) at different flow rates under turbulent flow regimes (2950 <=3D Re <=3D 8142). All the experiments were conducted to meet ASHRAE 93 (2010) standards. Heat transfer and the flow characteristics of nanofluids through the collector were studied, and empirical correlations were developed in terms of the Nusselt number, friction factor, and performance index. The convective heat transfer coefficient was improved up to 22.76% by using TiO2 nano fluids instead of the base fluid. It was found that TiO2 nanofluid with a volume concentration of 0.2% (at a mass flow rate of 0.0667 kg/s) can provide the maximum efficiency enhancement in the PTSC (8.66% higher than the water-based collector). Consequently, the absorbed energy parameter was found to be 9.5% greater than that of the base fluid. (C) 2017 Elsevier Ltd. All rights reserved.
Subramani, J.
Nagarajan, P. K.
Wongwises, Somchai
El-Agouz, S. A.
Sathyamurthy, Ravishankar
The present work investigated thermal performance and heat transfer characteristics of a solar parabolic trough collector using Al2O3/DI-H2O nanofluids. Nanofluids of varying concentrations (0.05% phi <=3D 0.5%) with mass flows (0.0083-0.05 kg/s) were considered for turbulent regime (2401 <=3D Re <=3D 7202) analysis. Experiments were carried out as per ASHRAE 93(2010) standards. By thermal performance analysis using Al2O3 nanofluid, it was understood that the collector efficiency improved up to 56% at a maximum volume concentration of phi =3D 0.5% and flow rate of 0.05 kg/s. The heat transfer study comparing Al2O3 nanofluid with pure water showed appreciable reduction in temperature gradient and surface temperature of the absorber. The heat transfer characteristics such as Nusselt number and friction factor relating to Reynolds number fits the experimental and predicted data and found within the limits of +/- 5.35% and +/- 9.61% for Nusselt number and friction factor respectively. Moreover, a similar empirical correlation was developed for collector efficiency, which was identified to be within the limit of +/- 1.02%. (C) 2017 American Institute of Chemical Engineers
MageshBabu, D.
Nagarajan, P. K.
Sathyamurthy, Ravishankar
Krishnan, S. Suseel Jai
This article communicates the thermal performance, heat transfer rate, and friction factor of Al2O3/DI water nanofluids at different concentrations in a micro-finned tube with tube helical inserts for different twist ratios. The thermal performance, heat transfer coefficient, and friction of the present study is also compared with a plain tube for validation. From the study, it is identified that the micro-finned tube with tube insert performance is higher as compared with a plain tube. Similarly, an empirical relation for Nusselt number (Nu) and friction factor (f) is estimated for straight twisted tube and left-right combination. The deviation between experimental and theoretical values for left-right twist and straight twist is found as 3 and 7% for Nusselt number and 7 and 9% for friction factor, respectively. Similarly, while analyzing the thermal performance, it was found that the maximum performance achieved was with a micro-fin tube with left-right twist with nanofluid concentration of 0.2%.
Kumar, S. Arun
Kumar, P. Suresh Mohan
Sathyamurthy, Ravishankar
Manokar, Muthu
Sun radiation is the heat energy source for solar still. That should be utilized maximum for increasing the evaporative rate at the top surface of the brine. The pyramid shape solar still (PSSS) can receive solar input radiation from all four directions. In this research, the top layer of conventional pyramid shape solar still (CPSSS) is covered with air-packed cover and analysed the effect in the modified still after air packed in between the two glasses, finally, that result is compared with the CPSSS. The air inside the two glasses will be receiving maximum radiation and retain in it. It can be used as top side insulation and which can ensure the maximum insulation for heat energy inside the PSSS. The CPSSS and air-packed pyramid shape solar still (APPSSS) were fabricated and experimented. The experiments were conducted at an ambient condition of the Chennai, Tamil Nadu (12.9416 degrees N, 80.2362 degrees E). The CPSSS gives good yield at evening when an increase in wind velocity. The APPSSS gives a lower performance as compared to the CPSSS due to the air-packed cover.