Numerical analysis of the thermo-hydraulic performance and entropy generation rate of a water-in-glass evacuated tube solar collector using TiO2 water-based nanofluid and only water as working fluids

A thermo-hydraulic performance and entropy generation rate comparison of a water-in-glass evacuated tube solar collector using TiO2 water-based nanofluid and water as working fluids is carried out by means of Computational Fluid Dynamics. A complete 3D geometry with variations of the solar radiation and inlet mass flow rates as operating conditions is considered. It was found that, the evacuated tube solar collector had a better performance in terms of outlet temperature and velocity using the nanofluid than using only water as working fluid. Also, the thermal and the exergy efficiencies are increased with the use of the nanofluid. The phenomena of viscous effects, heat transfer and heat loss in a global and local form are considered in the formulation of the entropy generation rate. The results of the local entropy generation rate due to the viscous effects and heat transfer are illustrated. Also, it was obtained that, using nanofluid as working fluid leads to a maximum reduction of the entropy generation rate of 87.5%, 65.5% and 14.71% due to viscous effects, heat transfer and heat loss, respectively. Finally, an improvement of the performance of the water-in-glass evacuated tube solar collector can be observed by using water-based nanofluid as working fluid.