Numerical study of natural convection of ZnO-water nanofluid enclosed between two inclined and concentric hemispheres

摘要

The main objective of this paper is to quantify natural convective heat transfer occurring between two concentric hemispheres differentially heated, through a ZnO-Water nanofluid whose volume fraction varies between 0 (pure water) and 10%. The inner active dome is an electronic device generating a constant heat flux leading to high Rayleigh numbers ranging between 2.31x107 and 7.21x1010 during operation. The outer cupola is kept isothermal at cold temperature. The base (disk) of the enclosure could be inclined with respect to the horizontal plane by an angle ranging from 0 degrees (horizontal position with dome oriented upwards) to 180 degrees (horizontal position with dome oriented downwards) by steps of 15 degrees. Calculations are realized by means of a 3D numerical approach based on finite volume method. Nusselt-Rayleigh-Prandtl correlations are proposed for two aspect ratios dome-cupola. They are valid for several configurations obtained by varying Rayleigh number, nanofluid volume fraction and tilt angle of the cavity. This new and original correlation allows thermal optimization of the treated assembly for application in various engineering fields as in electronics considered in the present work.