Natural convection between concentric and inclined hemispherical cavities filled with Cu-water nanofluid

Abstract

The hemispherical cavity is used for various applications in diverse engineering sectors. This is particularly acute for thermoregulation of electronic assemblies contained in the enclosures considered here, regardless of the shape of the heat source and the used fluid. This work quantifies and qualifies the dynamic and thermal phenomena occurring by natural convection between two concentric hemispheres. The external cupola is kept isothermal and the active internal hemisphere is an electronic assembly generating significant power during its operation. The latter lead to high Rayleigh number reaching 7.29×1010. The base (disc) of the assembly could be inclined with respect to the horizontal plane by an angle ranging from 0° (horizontal disc with dome facing upwards) to 180° (horizontal disc with dome facing downwards) depending on the application. The nanofluid used consists of water-base and copper nanoparticles, with a volume fraction varying between 0 (pure water) and 10%. The 3D numerical solution using a one-phase model is performed by means of the volume control method based on the SIMPLE algorithm. It highlights the improvement of the convective heat transfer by using this nanofluid. Calculations performed for many combinations of the Rayleigh number, inclination angle and volume fraction allowed to quantify the free convective heat transfer, presented by means of a correlation of the Nusselt-Rayleigh-Prandtl-inclination angle type.