Abstract
The transient three-dimensional numerical computations are carried out to clarify natural convective heat transfer characteristics of Al2O3-water nanofluids in a vertical cylindrical enclosure heated from below and cooled from above. Thermophysical properties of Al2O3-water nanofluids such as density, specific heat capacity, thermal expansion coefficient, viscosity, and thermal conductivity are estimated by the conventional prediction equations. Computed average Nusselt numbers of natural convection of Al2O3-water nanofluids decreased with the increase of the particle volume fraction compared to that of water. On the other hand, computed convective heat transfer rates of Al2O3-water nanofluids increased with the increase of the particle volume fraction compared to that of water. The increase of the convective heat transfer rates disagrees with the experimental results reported by Li and Peterson. Therefore, the natural convection computed by using the thermophysical properties of Al2O3-water nanofluids estimated with the conventional prediction equations cannot describe the heat transfer characteristics of nanofluids accurately.
