Résumé:
In this work, we have numerically analyzed the problem of heat transfer by laminar and permanent natural convection in an eccentric annular space filled with a hybrid nanofluid. The two internal and external cylindrical walls are maintained respectively at the temperature Th and Tc. The fluid is considered Newtonian and the flow is incompressible. The governing equations formulated in bipolar coordinates are written in terms of dimensionless equations. The resulting algebraic equations are discretized by the finite volume method and solved by a FORTRAN language. Numerical simulation is performed for Rayleigh numbers: Ra=103, 104, 105, different radiation numbers: Nr=0, 0.5, 1, 10, 25, 50, different volume fractions: 0-4 % and the geometry parameters (the angle of inclination α= 90°, the radius ratio r = 2.4 and the relative eccentricity e = 0.6. The results obtained show that increasing the volume fraction improves the transfer rate of heat for the considered values of the Rayleigh number. They also show that the average Nusselt number increases considerably with the increase in the radiation number and that the stability of the flow is improved by the presence of the radiation.
