A numerical study of nanofluid forced convection in ribbed channels

In this paper a numerical investigation on forced convection with nanofluids, composed by water and Al2O3 nanoparticles, in a two-dimensional channel is carried out. A uniform heat flux is applied on the external walls. A single-phase approach is employed to model nanofluids and the fluid properties are considered constant with temperature. The particle size is set equal to 38 nm and nanoparticle volume fractions from 0% to 4% are considered. The flow regime is turbulent and Reynolds numbers are in the range 20,000-60,000. Furthermore, square and rectangular shapes and different arrangements of ribs are analyzed in terms of different dimensionless heights and pitches of elements. The investigation is accomplished by means of Fluent code and its aim consists into find arrangements of ribs such to give high heat transfer coefficients and low pressure drops in presence of water-Al2O3 nanofluids. Results are presented in terms of temperature and velocity fields, and profiles of average Nusselt number, average heat transfer coefficients and required pumping power. Heat transfer enhancement increases with the particle volume concentration but it is accompanied by increasing required pumping power. The heat transfer improves, as Reynolds number raises, but also an increase of pumping power is observed. (C) 2011 Elsevier Ltd. All rights reserved.