Turbulent thermal convection of nanofluids in cubical enclosure using two-phase mixture model

Abstract

In this paper, numerical simulation is performed to investigate the turbulent thermal convection flow and heat transfer characteristics of nanofluids inside a cubical enclosure with partially mounted heat and cold source. A transient, three-dimensional, two-phase mixture model with LamBremhorst k−ϵ turbulence model is developed, validated and solved using finite difference method. The heat transfer performance of different water based nanofluids such as aluminum oxide (Al2O3), copper (Cu) and silver (Ag) are investigated for a wide range of Grashof numbers (Gr) varying between 106 ≤ Gr ≤ 1010. The nanoparticle diameter (dp) and volume fractions (ϕ) are varied between 20nm ≤ dp ≤ 80nm and 2% ≤ ϕ ≤ 4%. The results indicate that the random Brownian motion of nanoparticles increases the thermal convection and enhances the rate of energy exchange between the fluid and particle phase. The average heat transfer rate increases with increase in Grashof number and volume fraction. It is found that the effect of volume fraction on average heat transfer rate is more effective in transitional flows than fully turbulent flows. The average heat transfer rate increases with decrease in particle size and the influence of nanoparticle size on heat transfer enhancement are significant in turbulent flows than transitional flows.