The enhancement technologies in convection heat transfer allow the effectiveness improvement of heat exchangers. The employment of rough surfaces could be taken into account. In fact, in a ribbed channel, turbulators break the laminar sub-layer and create local turbulence in order to reduce the thermal resistance and augment heat transfer rates. Another available technique is represented by the introduction of nanoparticles in the base fluids in order to improve the fluid thermal conductivity. However, both the methods provide increasing pressure drops.
In this paper a numerical investigation is carried out on water-Al2O3 nanofluid forced convection in a two-dimensional ribbed channel, heated by a constant heat flux. Ribs have trapezoidal shapes and different geometric arrangements were analyzed. The mixture model was employed in order to describe the nanofluid behaviour and different nanoparticle volume fractions were considered. The aim consists into describe the thermal and fluid-dynamic performances of ribbed channels filled with Al2O3/water based nanofluids in the turbulent regime. Results show increasing heat transfer rates as particle concentrations and Reynolds numbers increase but higher required pumping powers.