Numerical study of laminar mixed convection of a nanofluid in a horizontal tube using two-phase mixture model

Laminar mixed convection of a nanofluid consists of water and Al2O3 in a horizontal tube has been studied numerically. Two-phase mixture model has been used to investigate hydrodynamic and thermal behaviors of the nanofluid over wide range of the Grashof and Reynolds numbers. Comparisons with previously published experimental and numerical works on mixed convection in horizontal tubes show good agreements between the results. For a given particles mean diameter the effects of nanoparticles volume fractions on the hydrodynamics and thermal parameters are presented and discussed. It is shown that at the fully developed region the nanoparticle concentration does not have significant effects on the hydrodynamics parameters. However, its effects on the thermal parameters are important. Concentration of the nanoparticles is higher at the bottom of the tube and also at the near wall region. (c) 2007 Elsevier Ltd. All rights reserved.