Nanoparticle Concentration in Buoyancy Flows
The presence of nanoparticles in buoyancy-driven flows affects the thermophysical properties of the fluid and consequently alters the rate of heat transfer. The focus of this paper is to estimate the range of volume fractions that results in maximum thermal enhancement in buoyancy-driven nanofluids. In this study, a two-dimensional rectangular enclosure with isothermal vertical walls and adiabatic horizontal surface is filled with 27nm Al2O3 - H2O nanofluid. The volume fraction is varied between 0 to 12%. Results shows that for small volume fraction, 0.2≤Φ≤2%, the presence of the nanoparticles does not impede the free convective heat transfer, rather it augments the rate of heat transfer. However, for large volume fraction, Φ>2%, the convective heat transfer coefficient declines due to reduction in the Rayleigh number but the rate of thermal diffusion is enhanced.