Abstract
The effects of two kinds of base fluid (H2O and Ga) and three different nanoparticle radiuses (20nm, 40nm and 80nm) on the natural convection heat transfer of a rectangular enclosure filled with Al2O3–H2O and Al2O3–Ga nanofluid at different Rayleigh numbers (Ra=103 and Ra=105) are discussed based on a two-phase lattice Boltzmann method in this paper. It is found that Al2O3–Ga nanofluid shows a better heat transfer enhancement than Al2O3–H2O nanofluid. Al2O3–Ga and Al2O3–H2O nanofluid with the same smallest radius (r=20nm) can enhance the heat transfer by 86.0% and 24.5% compared with water respectively. It is also found that Al2O3–Ga nanofluid at low Rayleigh number (Ra=103) shows the biggest heat transfer enhancement (shows a 4.4% increase for every nanoparticle radius decreasing 20nm) compared with Al2O3–H2O nanofluid. The enhancement ratio at low Rayleigh number is about 3–10.8% and 23.5–28.8% more than that at high Rayleigh number for Al2O3–water and Al2O3–Ga nanofluid respectively. In addition, the nanoparticle fraction distributions in the enclosure are also investigated.
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