A numerical study of mixed convection flow and heat transfer of Copper (Cu)-water nanofluid inside an eccentric horizontal annulus is presented. The inner and outer cylinders are kept at constant temperatures as Th and Tc, respectively. The inner cylinder rotates to generate the forced convection effect. The numerical work was carried out using an in-house CFD code written in FORTRAN. Different scenarios were explored to explain the effects of different parameters on the studied problem. These parameters are Richardson number, eccentricity ratio, and solid volume fraction. The range of the Richardson number Ri, solid volume fraction of the nanoparticles ?, and the eccentricity ratioe, are 0.01 ? Ri ? 100 (natural convection), 0 ? ? ? 0.05, 0 ? e ? 0.9 respectively. All results were performed with thermal Grashof number Gr, and radius ratio Rr, equaled to 104 and 2, respectively. The effects of eccentricity, nanoparticles volume fraction, and Richardson number on the average Nusselt number, streamlines and isotherms were investigated. Results were discussed, and were found to be in good agreement with previous works. It was also found that, the eccentricity has a positive remarkable effect on the average Nusselt number, while the effect of nanoparticles concentration was more pronounced at mixed convection region (Ri=1).

Partially open cavities are encountered in various engineering systems such as electronic cooling devices and cooling for gas turbine blades, instead of conventional film cooling slots. Flow is to be imparted over the partially open cavity where it induces a shear layer and a shear driven vortex within the cavity, which is subjected to cooling effect at its wall. Depending on the opening ratio, heat and mass transfer occur between the main flow and the trapped vortex through the shear layer. In the present study, RANS simulations of such flow have been conducted for circular and square cavities to investigate the effect of opening ratio on the heat and mass transfer characteristics. The simulations were established on a rigorous numerical approach and proper validation with laser Doppler velocimetry measurements of turbulent flow in circular cavity. Based on the hydraulic diameter of the cavity, opening ratios ranging from 0.2 to 1.0 were investigated for a Reynolds number of 3?105. Generally, the maximum Nusselt number was achieved at higher opening ratios for both circular and rectangle cavities. On the other hand, the maximum dimensionless temperature gradient, ?, inside the cavity was achieved at L/D = 0.2 for both cavity configurations.