Natural Convection in a Porous Horizontal Cylindrical Annulus Under Sinusoidal Boundary Condition

In the present work, a numerical study of the heat transfer by transient convection in a horizontal annulus sinusoidal heated. The annulus is between two concentric horizontal cylinders and filled with liquid-saturated porous media. Darcy-Brinkman model is implemented to describe the fluid flow in the annulus. The study is performed based on the Rayleigh number Ra range of 40 ≤ Ra ≤200, and aspect ratio 1.5 ≤ AR ≤2.5. The present model was validated with literature, and good agreement was obtained. Also, the mesh test was performed to ensure the mesh size does not influence the obtained results. The results are presented in terms of isothermal lines, streamlines, and average Nusselt number Nu. Conduction is found to dominate after starting the heating and before ending it. At the peak time and around it, convection dominates in the annulus. The obtained results show an enhancement of up to 69% in Nu as Ra increases from 40 to 200 at AR=2.5. Increasing AR also enhances Nu by 46% as AR increases from 1.5 to 2.5 at Ra=200.