Surfactants role in the enhancement of the heat transfer and stability of alumina oxide – distilled water nanofluid was introduced in this research, where there are limited studies that conjugate between the stability improvement and its effect on the heat transfer coefficients. Four weight concentrations for the experiment were used (0.1, 0.3, 0.6, and 0.9%) with 20 nm particle size under a constant wall temperature. The selection of appropriate surfactants weight was tested too by implementing three weight concentrations (0.5, 1, 1.5, and 2 %) related to each nanofluid concentration via measuring their effect on the zeta potential value. The heat transfer augmentation was tested through a double horizontal pipe under a constant wall temperature at entrance region with Reynolds number range (4000–11800). The results manifested the use of nanofluid worked on enhancement the heat transfer performance better than water, and the stable nanofluid elucidated better results.
Solar energy is one of the most important types of renewable energy and is characterized by its availability, especially in Iraq. It can be used in many applications, including supply thermal energy by solar collectors. Improving the thermal efficiency of solar collector leads to an increase in the thermal energy supplied. Using a nano-fluid instead of base fluid (water is often used) as a working fluid is a method many used to increase the thermal efficiency of solar collectors. In this article, the latest research that used nano-fluid as a working fluid in evaluating the thermal efficiency of solar collector, type flat plate was reviewed. The thermal efficiency improvement of flat plate solar collector was reviewed based on the type of nanoparticles (metal oxides, semiconductors oxides, carbon compounds) used in the base fluid and comparison was made between these nanoparticles under the same conditions. Moreover, the effect of varying the concentration of nanoparticles in the base fluid and changing the working fluid flow rate on the thermal efficiency of flat plate solar collector was also reviewed. The results of the review showed that nano-fluids containing carbon compounds are better than other nano-fluids and that copper oxide is better than the rest of the metal oxides used in improving the thermal efficiency of flat plate solar collectors.
This study presents a solution to the selection of the optimum orientation for non-tracking solar photovoltaic panels and non-tracking solar thermal collectors with a new methodology in Baghdad city. The optimum tilt angle of solar application was determined monthly, seasonal and yearly based on the largest monthly average daily total solar radiation incident on the surface in Baghdad. The solar radiation and tilt angle were calculated theoretically with the help of MATLAB R2016b and the theoretical data of solar radiation were validated via comparison with experimental data. The optimum tilt angle results of months have been ranging as follows: from 3.77˚ for June to 62.88˚ for December, moreover the optimum tilt angle results for the seasons and year have been as follows: 60.41˚, 38.88˚, 5.26˚, 31.34˚ and 33.97˚ for winter, spring, summer, autumn and annual respectively, and best directing the fixed solar applications toward the south. The results were compared with previous studies and showed an increase in monthly average daily total solar radiation for all months except for April and September.
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