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The current numerical study is aimed to examine the forced convection heat transfer of fly ash-Copper (80:20% by volume) water-based hybrid nanofluids flowing in a horizontal circular copper tube under a constant heat flux of 7962W/m2 using STAR CCM+ software. The volume concentrations of 0.5% and 1% are considered for the analysis within the Reynolds number range of 6900-26500. The findings show that the heat transfer coefficient and the Nusselt number of hybrid nanofluid at a concentration of 1 vol.% are increased by about 66.0% and 36.67% compared to that of water.

STAR CCM+ software is used to investigate the forced convection heat transfer of fly ash/Water nanofluids flowing through a horizontal circular tube in the turbulent flow regime under the constant heat flux of 707 W/m2. The volume concentrations of nanofluid are 0.3, 0.5, 1.0, and 1.5 vol. %, used in this analysis. The results revealed that both the Reynolds number and concentration intensify the Nusselt number of fly ash nanofluids. The highest heat transfer coefficient augmentation is about ∼60% observed at 1.5% concentration in comparison to the water.

Simulation by convenient software, the same as FLUENT, was used to predict the friction factor and Nusselt number for forced convection heat transfer of TiO2-water nanofluid. The range of Reynolds number is from 10000 to 100000 to be turbulent flow in a horizontal straight tube with heat flux 5000 w/m2 around it. The volume fraction of nanoparticle was (0.25%, 0.5%, 0.75% and 1%) and diameter of particle is 27 nm. The results show that the friction factor and Nusselt number are increasing with increasing of volume fraction. Results compared with the experimental data available in literature and there are good agreements.

The thermo-physical properties of nanofluids such as thermal conductivity, viscosity, density and specific heat of nanofluids are required for the analysis of convection heat transfer coefficients. The density and specific heat of nanofluids can be estimated with the mixture relations in literature. Information regarding the properties at different volume concentration and temperature is required for the estimation of heat transfer coefficient. The two most fundamental properties which are, experimentally, determined, are viscosity and thermal conductivity. Investigators have been determining the properties of nanofluids at different temperatures and base liquids. The present work is an attempt to analyze the available data to develop a non-linear regression equation for the estimation of thermal conductivity and viscosity of water based nanofluids. In the present study, nanofluids are considered as a homogenous medium and the parameters influencing the thermo physical properties identified. Equations are developed for the analysis of thermo-physical properties of nanofluids as a function of parameters viz., material, concentration, temperature and particle size useful for designer. The opposing nature of thermal conductivity rise and viscosity decrease with temperature; dependence of nanofluid thermal conductivity on material properties alters the range of applicability of nanofluids for heat transfer applications. The thermal conductivity and viscosity of Al2O3, ZnO and TiO2 dispersed in water are measured to validate the proposed equations. The result shows that the equations are able to predict the thermal conductivity and viscosity of different types of nanofluids of different particle diameters closely.