Comparative assessment of single and two-phase models for numerical studies of nanofluid turbulent forced convection

Numerical predictions by single-phase and three different two-phase models (volume of fluid, mixture, Eulerian) of nanofluid turbulent forced convection in a horizontal tube with uniform wall heat flux are evaluated by comparison with two different sets of experimental data. The elliptical, coupled, steady-state, three-dimensional governing partial differential equations are solved using the finite volume scheme. Six combinations of correlations for viscosity and conductivity of nanofluids are compared for the single phase approach. The combination giving the best agreement with the experimental data is chosen for the rest of the comparisons. In the case of the two-phase models, results for two outlet boundary conditions are obtained. The one with better convergence and lower uncertainties is chosen for the comparison with the single phase model. The comparison of the predictions by the single-phase model with the best property correlations and by the two-phase models with the best outlet condition favours the former. Since the single-phase model is also simpler to implement and requires less computer memory and CPU time it is concluded that it is more appropriate for the conditions under study.