Developing mixed convection of a nanofluid in a horizontal tube with uniform heat flux

Purpose - This paper seeks to show the effect of using nanofluid on mixed convection heat transfer in a horizontal tube. Design/methodology/approach - Three-dimensional elliptic governing equation has been solved using finite volume approach. Grid independence test has been performed to find the suitable grids. Obtained numerical results have been validated with the available experimental and numerical results in the literature. Parametric study has been done to see the effects of Reynolds number, Grashof number and volume fraction of the nanoparticles on the hydrodynamic and thermal parameters in a horizontal tube. Findings - The nanoparticles volume fraction does not have a direct effect on the secondary flow and the skin friction coefficient. However, its effect on the entire fluid temperature causes the strength of the secondary flow to reduce. For a given Grashof number, increasing the particles' concentration augments convective heat transfer coefficient. It does not have a significant effect on the skin friction coefficient at the low Grashof number. However, skin friction coefficient is slightly affected at the higher Grashof numbers. Research limitations/implications - The Grashof number is limited for which the Boussinesq hypothesis for the variation of density with the temperature would be valid. Practical implications - This paper promotes designing heat exchangers, solar collectors, cooling electronic devices. Originality/value - Nanofluid mixed convection in a horizontal tube has been studied and the effects of nanoparticles concentration on the hydrodynamic and thermal parameters have been shown and discussed.