Effect of Aspect Ratio on Heat Transfer in a Differentially Heated Square Cavity Using Copper-Water Nanofluid

Effect of aspect ratio (AR) on heat transfer due to laminar natural convection of Cu-water nanofluid in a two-dimensional differentially heated enclosure has been studied numerically. The transport equations have been discretized using finite volume approach and solved using SIMPLER algorithm. Considering the nanofluid to be incompressible and non-Newtonian, the shear stresses have been calculated using Ostwald-de Waele model. The thermal conductivity of the nanofluid has been calculated from the proposed model by Chon et al. Study has been conducted for AR ??0.125 to 3 while Rayleigh number (Ra) has been varied between 104 and 107 and solid volume fraction (ϕ) of copper particles (diameter = 25 nm) varied from 0.05% to 5%. In general heat transfer decreases with increase in AR and ϕ but increases with increase in Ra. For Ra = 107, maximum heat transfer is obtained between AR = 0.15 - 0.25.