Investigation of heat transfer characteristics in the developing and the developed flow of nanofluid inside a tube with different entrances in the transition regime

Abstract

In this paper, we studied heat transfer characteristics in the developing and the developed flow of nanofluid inside a tube with different entrances in the transition regime. A range of Reynolds numbers from Re = 500 to 13,000 was stimulated to examine flow characteristics in the tube. Effect of entrance, diameter of nanoparticles, nanoparticle type, Reynolds number and concentration of nanoparticles on onset of transition were studied. The results show that heat transfer coefficient and Nusselt number of base fluid and the nanofluid increase with increasing Reynolds number. Also, convective heat transfer coefficient of nanofluid increases by increasing Reynolds number, and the rate of increase in heat transfer coefficient varies depending on diameter, volume fraction and type of nanoparticles. Furthermore, the results show that local Nusselt number and local convective heat transfer coefficient slightly decrease with increasing particle diameter at constant volume fraction of nanoparticles.