Experimental and numerical investigations on the effect of Al2O3/TiO2H2O nanofluids on thermal efficiency of the flat plate solar collector

In this study, the effect of using nanofluids on the thermal efficiency of a flat plate solar collector (FPSC) is investigated numerically and experimentally. The results of numerical studies conducted by the open source Computational Fluid Dynamics (CFD) software have good agreement with the experimental results. The studied nanofluids were Al2O3H2O (20 nm 0.1 wt%), TiO2H2O (15 nm 0.1 wt%), and their mixture with equal ratio. The nanofluids were prepared based on two-step method and cetyltrimethylammonium bromide (CTAB) was used as a surfactant. Volume flow rates were 1.5 l/min, 2.0 l/min and 2.5 l/min. Experimental results show that by using Al2O3 (0.1 wt%), TiO2 (0.1 wt%) and the mixture of these two nanofluids, the thermal efficiency will enhance about 19%, 21% and 26%, respectively (compared with water as a working fluid). A mixture of the two nanofluids attains the best thermal performance compared to the two other nanofluids. Since TiO2 is more expensive than Al2O3 Nanopowder, using the mixture of them is more economical with better thermal efficiency. Increasing the concentration of the nanofluid mixture from 0.1 wt% to 0.2 wt% will result in approximately 5% improvement in the thermal efficiency of the solar collector. Also, the thermal efficiency will be intensified by volume flow rate.