Forced Convection Enhancement in Channels with Transversal Ribs and Nanofluids

A numerical investigation on turbulent forced convection in nanofluid mixture, water-Al2O3, in a symmetrically heated channel with ribbed upper and lower walls is carried out. Different geometric rib arrangements with triangular, rectangular and trapezoidal shapes are analyzed. The governing equations are written assuming the mixture model to describe the nanofluid behavior in a two dimensional channel heated by a constant wall heat flux. Finite volume method is used to solve the model equations. Simulations for different nanoparticle volumetric concentrations from 0%, pure water, to 4% and Reynolds numbers between 20,000 and 60,000 are accomplished. As general conclusion, it is observed that the heat transfer rate increases as nanoparticle volume fraction and Reynolds number increase but higher pumping powers are required. The comparisons allow to determine that triangular ribs present higher thermal performances than the trapezoidal ones but also higher pressure losses. Moreover, the rectangular-trapezoidal-shaped rib shows the best performance at a pitch-rib height equal to 10.