Numerical study of turbulent nanofluid flow at the entrance region of a ribbed pipe

Abstract

In this paper, we perform a numerical study on the heat transfer and pressure drop in hydraulically and thermally developing turbulent flow of nanofluid through an internally ribbed pipe. The effects of volume fraction of nanoparticles and the distance between the ribs are investigated on the heat transfer and skin friction coefficients at the entrance region of the pipe. The set of governing equations followed by a two-layer zonal turbulence model are solved numerically by a velocity-pressure coupling algorithm based on finite-volume method. Moreover, available empirical relations are used to calculate the nanofluid properties in terms of the nanoparticles and the base fluid. The obtained results illustrate that increasing the volume fraction of nanoparticles makes the thermal entrance length decrease and consequently, the heat transfer increases. It reveals that 10% increase in the volume fraction of nanoparticles causes about 15% rise in average Nusselt number. In addition, it is found that the friction factor rises by increasing the volume fraction of nanoparticles compared with turbulent flow of the base-fluid. Also, the average Nusselt number in nanofluid flow increases with the interval between the ribs compared with pure-fluid flow.