Developing laminar mixed convection of nanofluids in an inclined tube with uniform wall heat flux

Purpose - The aim is to study the conjugate problem of developing laminar mixed convection flow and heat transfer of water-Al2O3 nanofluid inside an inclined tube submitted to a uniform wall heat flux. Design/methodology/approach - The set of non-linear, coupled and fully elliptic governing equations has been solved using a 'finite-control-volume' numerical method, the classical power-law scheme for computing heat and momentum fluxes staggered and non uniform grids for spatial discretization of various regions of the tube. Findings - Numerical results have shown that the presence of nanoparticles slightly intensifies the secondary flow due to buoyancy, in particular in the developing region. It also increases the average Nusselt number and decreases slightly the product ReCf with respect to those of water. For the horizontal inclination, two new correlations have been proposed to calculate these two variables in the fully developed region, for Grashof number ranging from 10(3) to 10(5) and particle volume concentrations up to 7 per cent. Practical implications - The results of this study can be employed for various practical heat transfer and thermal applications using nanofluids. Originality/value - The present study constitutes an original contribution to the knowledge of nanofluid thermal behaviour.