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Macroscopic modeling of hydrodynamic behavior of nanofluid flow in a uniformly heated circular pipe is considered. Single-phase models with Brownian and dispersion viscosity models are evaluated by comparing predicted pressure drop and apparent friction factor with experimental and two-phase Eulerian-Eulerian model results from literature. Single-phase models are capable of predicting heat transfer of nanofluids better when dispersion models are used. However, they fail to accurately predict pressure drop when used with standard viscosity models. Two-phase models on the other hand, can accurately predict both thermodynamic and hydrodynamic field at the expense of computational time. A new viscosity model, which is based on dispersion viscosity, is proposed to increase accuracy of single-phase models in predicting hydrodynamic field of nanofluid flow. Results suggest that single-phase dispersion viscosity model is the most accurate single-phase model.

Hydrodynamic and thermal characteristics of Al2O3 – water nanofluid flow at entry region of a uniformly heated pipe are studied applying finite control volume method (FCV). Single phase and Eulerian-Eulerian two-phase models were used in modelling of nanofluid flow and heat transfer. The two methods are evaluated by comparing predicted convective heat transfer coefficients and friction factor 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. Two-phase model predicts convective heat transfer coefficient and friction factor more accurately at the entry region. Moreover, computational cost can be reduced by implementing Full Multiphase Coupled scheme.