Renewable Energy Resources and Technologies
Mohamed Ramadan Gomaa; Njoud Hussein Alhabahbh; Mohammed Abbas Al-Nawafleh
Abstract
This research reviews various studies on the effect of using nanofluids in evacuated tube solar collectors (ETSC). The initial segment of this study elaborates on the importance of using the ETSCs and categorizes these collectors in terms of classification and application. The second segment evaluates ...
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This research reviews various studies on the effect of using nanofluids in evacuated tube solar collectors (ETSC). The initial segment of this study elaborates on the importance of using the ETSCs and categorizes these collectors in terms of classification and application. The second segment evaluates the physical properties of nanofluids incorporated in the solar system collector and presents some applications of nanofluids. The last segment of the research reviews the works of a group of researchers who have already applied nanofluids to evacuated tube solar collectors for various purposes, including increasing the heat transfer coefficient and improving efficiency. Among the prevalent nanofluids employed in solar applications, Al2O3, CuO, and TiO2 feature prominently, whereas Ag, WO3, and CeO2 find limited application in the solar context. Furthermore, nanofluids within the size range of 1–25 nm, 25–50 nm, and 50–100 nm constitutes 54%, 25%, and 11% of the applications, respectively. Particularly noteworthy, the single-walled carbon nanotubes/water (SWCNT/water) heat pipe showcases the most remarkable efficiency enhancement, achieving an impressive 93.43% improvement.
Renewable Energy Resources and Technologies
Najmeh Salehi; Arash Mirabdolah Lavasani; Ramin Mehdipour; Mohammad Eftekhari Yazdi
Abstract
One of the best and most important types of concentrating solar power plants is the linear Fresnel collector. The thermal performance and application of absorber in a solar power plant can be enhanced using direct steam generation technology. A particular discrepancy between the present study and others ...
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One of the best and most important types of concentrating solar power plants is the linear Fresnel collector. The thermal performance and application of absorber in a solar power plant can be enhanced using direct steam generation technology. A particular discrepancy between the present study and others lies in our attempt at applying a new method for calculating critical heat flux based on Look-up Table. In the current study, effects of nanofluid on the length of the critical heat flux and convection heat transfer coefficient were investigated. The nanoparticles considered in this study were aluminum, silver, nickel, and titanium dioxide at concentrations of 0.01, 0.1, 0.3, 0.5, 1 and 2 %. Modeling results revealed that the heat transfer coefficient increased upon enhancing the volumetric concentration of nanoparticles, thereby improving this coefficient at 2 vol. % nickel nanoparticles, which was 10.6 % above the value of pure water. On the other hand, thermal efficiency was enhanced when nickel nanoparticles were dispersed in pure water such that increase rates of thermal efficiency equaled 11.2, 10.8 and 11.3 % in the months of June, July, and August, respectively, when the volume concentration of nanoparticles was 0.5 %.
Renewable Energy Resources and Technologies
Seyed Amir Hossein Zamzamian; Mohsen Mansouri
Abstract
The enhancement of the thermal performance of Vacuum Tube Solar Collectors (VTSC) was studied by using alumina nanofluid as working fluid. VTSC is a simple and commonly utilized type of collector. This study established the heat transfer experimental model of all glass VTSCs used in a forced-circulation ...
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The enhancement of the thermal performance of Vacuum Tube Solar Collectors (VTSC) was studied by using alumina nanofluid as working fluid. VTSC is a simple and commonly utilized type of collector. This study established the heat transfer experimental model of all glass VTSCs used in a forced-circulation solar water heating system using alumina nanofluid as base fluid. Al2O3 (with an average particle size of 15 nm) nanoparticles were provided and utilized to prepare nanofluids at a low mass concentration (0.5–1 wt.%). The thermal performances of VTSC were 15.3%, 25.7%, and 27.2% for the deionized water and Al2O3/water nanofluids with 0.5 and 1.0 wt. % as the working fluid, respectively. Generally, for Al2O3/water nanofluids with mass concentrations of 0.5 and 1.0 wt. %, the thermal performance increased by 67.9% and 77.7%, respectively, superior to that of vacuum tube using deionized water as the working fluid. Experimental results also showed that, for all three experimental tests, the thermal efficiency of the VTSC would increase by enhancing the average solar radiation.
S. Zeinali Heris; Farhad Oghazian; Mahmoud Khademi; Effat Saeedi
Abstract
In this study, the convective heat transfer and pressure drop in laminar flow of Al2O3/water and CuO/water nanofluids through square and triangular cross-sectional ducts have been numerically investigated using new technique. It has been assumed that there is constant heat flux boundary condition at ...
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In this study, the convective heat transfer and pressure drop in laminar flow of Al2O3/water and CuO/water nanofluids through square and triangular cross-sectional ducts have been numerically investigated using new technique. It has been assumed that there is constant heat flux boundary condition at walls. In addition, to include the presence of nanoparticles, the dispersion model has been used, and the system was solved numerically. Results show that by increasing the volumetric concentration and decreasing the size of nanoparticles, Nusselt number has been enhanced. Also, the Nusselt number increases by increasing the Reynolds number. In all cases, it has been observed that heat transfer coefficient of nanofluid increases in comparison with heat transfer coefficient of pure water. The results show that by adding nanoparticles, pressure drop increases in ducts. In square and triangular ducts, pressure drop is higher when we use CuO/water nanofluid instead of Al2O3/water nanofluid. In the same way, pressure drop increases by increase of faces of non-circular ducts.
