Single-phase models for improved estimation of friction factor for laminar nanofluid flow in pipes

• Laminar nanofluid forced convection in circular pipe subject to constant heat flux.
• Prediction of friction coefficient by single phase models evaluated.
• Single phase methods unable to predict increase in friction coefficient.
• Use of single phase dispersion model introduced for prediction of friction factor.
• Single phase dispersion model predicts friction coefficient accurately.

Hydrodynamic and thermal modeling of nanofluid flow in a uniformly heated circular pipe is considered using single-phase models. Various single-phase models relying on Brownian and dispersion viscosity models are evaluated by comparing heat transfer coefficient, Nusselt number and friction factor with experimental 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 surface shear stress when used with standard viscosity models. A new viscosity model based on dispersion viscosity is proposed to improve prediction accuracy of single-phase models for estimating the surface shear stress of laminar nanofluid flow. Results suggest that proposed single-phase dispersion model is capable of accurately predicting heat transfer coefficient and friction factor.