Comparison of single and two-phase models for nanofluid convection at the entrance of a uniformly heated tube

Macroscopic modeling of hydrodynamic and thermal behavior of nanofluid flows at the entry region of uniformly heated pipe is studied. Single-phase models with and without thermal dispersion effect, Eulerian-Eulerian, and Eulerian-Mixture two-phase models are evaluated by comparing predicted convective heat transfer coefficients and friction factors with experimental results from literature. Solutions with two different velocity pressure coupling algorithms, Full Multiphase Coupled, and Phase Coupled Semi-Implicit Method for Pressure Linked Equations are also compared in terms of accuracy and computational cost. Dispersion model that uses velocity gradient to define dispersion conductivity is found to be more effective at entry region compared to other single-phase models. However, two-phase models predict convective heat transfer coefficient and friction factor more accurately at the entry region. Moreover, computational cost of Eulerian-Eulerian two-phase model can be reduced up to 50% by implementing Full Multiphase Coupled scheme. (C) 2014 Elsevier Masson SAS. All rights reserved.