Solar energy storage in evacuated tubes solar collector using nanofluid embedded in a saturated porous media in the fully developed region: Al<sub>2</sub>O<sub>3</sub> nanofluid embedded in graphite as a saturated porous media

Abstract

<abstract> The evacuated tube solar collector is considered an efficient, convenient, and economical option used to convert solar energy into heat. In this work, enhancement of evacuated tubes solar collector performance and the potential for energy storage by using Al₂O₃ water-based nanofluid embedded in Graphite as a saturated porous media was presented and studied theoretically. The Governing equations derived from the principles of conservation of mass, momentum, and energy were written in a dimensionless form, and solved these equations analytically for the fully developed region, and numerically throughout the entrance region, and the heat flux data for Amman, Jordan was used in this study. The analysis of the effect of different parameters as porosity, pore diameter, nanoparticles solid volume fraction, pressure, and radius of conduit on temperature variation through the pipe and Nusselt number was done. The results show that the flow of nanofluid in porous media enhances the evacuated tube's performance compared to just using water in the same medium under the same conditions. In August, the temperature variation in the evacuated tube at the same condition for Al₂O₃ water-based nanofluid for 1.5% volume fraction reach 42 ℃ and 73 ℃ for 6% volume fraction. In contrast, In January for the 1.5% volume fraction the temperature variation reached 25 ℃ and 43 ℃ for 6% volume fraction. On the other hand, the stored energy approximately reached 30 kJ/kg and 45 kJ/kg for solid volume fraction 1.5% and 6% respectively at the same conditions. </abstract>