Numerical investigation of turbulent nanofluid flow effect on enhancing heat transfer in straight channels

Abstract

Turbulent friction and heat transfer behaviors of magnetic nanofluid (Fe3O4 dispersed in water) as a heat transfer fluid in three different cross sectional channels (circular, rectangular and square) was investigated numerically. The channels with hydraulic diameter of 0.014 m and 1.7 m length subjected a uniform heat flux (13500 w/m2) on all their walls has been presented in order to determine the effects of geometry change, nanoparticle concentration and flow rate on the convective heat transfer and friction factor of nanofluid with neglecting the effect of magnetic flow field. Fe3O4 nanoparticles with diameters of 36 nm dispersed in water with volume concentrations of 0–0.6 vol. % were employed as the test fluid. The investigation was carried out at steady state, turbulent forced convection with the range of Reynolds number varied from 5000 to 20000, three dimensional flow, and single phase approach. Computational fluid dynamics (CFD) model by using FLUENT software depending on finite volume method was conducted. In this study, the result exhibited that the Nusselt number of nanofluid for all geometries is higher than that of the base liquid and increased with increasing the Reynolds number and particle concentrations. But the circular pipe had the highest value of Nusselt number followed by rectangular and square tube. On the other hand, for the friction factor, the results revealed that the friction factor of nanofluids was higher than the base fluid and increases with increasing the volume concentrations and decreases with increasing of Reynolds number. In addition the friction factor of square channel is higher than others followed by rectangular and circular channel, respectively.