Mixed Convection of Hybrid Nanofluid in Inclined Annulus Subjected to Solar Radiation

Abstract

The problem investigated in this paper consists of the mixed convection of the Ag–ZnO (50%–50%)/water hybrid nanofluid in an inclined annular space; the upper part of the outer wall is exposed to solar radiation. Based on experimental data, new temperature-dependent expressions have been developed in this work to calculate dynamic viscosity and thermal conductivity. The governing equations were solved using the Fluent solver based on the finite volume method. Results show that Ag–ZnO/water has the highest Nu number compared to pure water and ZnO/water for all studied values of Ri number (0.3, 0.7, 1, 1.3, 1.7, 2) and volume concentration (0.01 and 0.02). However, the volume concentration effect on the friction coefficient is negligible for less than 0.15. Inhomogeneous solar radiation distribution at the wall has a very strong effect on the variation of the dynamic and thermal quantities. Temperature variations are more important above the horizontal diameter. In addition, the secondary flow has a direct impact on velocity variations. This effect results in the appearance of two symmetric vortices above the horizontal diameter. Vortices velocity increases with the Ri number increase. Considering tilt angle, obtained results show that its effect on dynamic quantities is more important.