Natural Convection Heat Transfer of Nanofluid around Circular Cylinder Located in an Octagonal Enclosure

The present work deals with a numerical study of natural convection heat transfer in an octagonal enclosure filled with Al2O3/water nanofluid with internal circular heat source. The outer cylinder is isothermally cooled at temperature TC and the inner cylinder is isothermally heated at Th. The governing equations are discretized using the finite volume method and solved by Ansys 19.2 commercial program. The ranges of Rayleigh number and volume fraction are 104 ≤ Ra ≤ 106 and 0 ≤ 𝜑 ≤0.1; respectively. Results were presented in terms of streamlines, isotherms, and local average Nusselt numbers. The effects of Rayleigh number, position of inner cylinder, and nanoparticles volume fraction on the behavior of thermal patterns, flow fields, and average heat transfer rates will be presented and discussed.