The effect of ribs spacing on heat transfer in rectangular channels under the effect of different types of heat flux in the Presence of a nanofluids

Abstract

In this study, numerical computations of the influence of adding ribs in a rectangular channel on the forced convection heat transfer and laminar fluid flow characteristics have been carried out. The analysis was carried out by using the finite element method to solve the dimensionless governing equations for the twodimensional channel with 80 mm height and 2000 mm length at the Reynolds number of (10, 100, and 500), rib height e=8mm with different aspect ratios (AR =2.5, 3.125, 3.75, 4.375, and 5). Also, the study compared two cases of investigations with and without nanofluid (Water/ TiO2) at the volume fractions of nanoparticles of 0, 2 and 4%. The results concluded that, for certain arrangements, the use of extended surfaces within a rectangular channel can significantly enhance the rate of heat transfer and when the aspect ratios decreases, the Nusselt number increased. However, the existence of ribs within channel in case of constant heat flux can cause a significant improvement of heat transfer compared to that in the corresponding channel under the variable heat flux.