Numerical approach of natural convection in eccentric annular spaces filled with hybrid nanofluids

Abstract

A numerical analysis of free convection in two horizontal eccentric cylinders filled with aAl2O3-TiO2
/water hybrid
nanofluid is performed in this paper. The two internal and external cylindrical walls are maintained respectively at the
temperature Th
and Tc
with Th
>Tc
. Theoretical correlations for the thermal conductivity and viscosity of the hybrid nanofluid
were used in this study. The problem is treated by dimensionless governing equations which areformulated in bipolar
coordinates and solved by the finite volume method. The effects of the Rayleigh number and the hybrid nanoparticles
volume fraction on the natural convective heat transfer are examined. The results are shown as isotherms and streamline
contours, as well as average and local Nusselt number profiles. It was found that the inclusion of the hybrid nanoparticles in
the base fluid produced an increase in the heat transfer rate. In addition, increasing the volume fraction of the hybrid
nanoparticles improves the heat transfer rate for all Rayleigh number values.