The effect of nanoparticles on heat transfer of a flow which was contained water-based aluminum, titanium and carbon nanotubes (including 0.024, 0.023 and 0.0014 vol/vol of Al, Ti and CNT respectively) with laminar regime flowing in a horizontal tube with constant heat flux at the wall was investigated by means of Computational Fluid Dynamics (CFD). The Nusselt number for all considered nanofluids was also calculated using novel equations and then results were compared with classical correlation for liquids. It was demonstrated that Nu numbers calculated from the result of this modeling have lower values than those of calculated from classical correlations, but novel equations introduced in this paper could correctly predict Nu numbers. Also, it was concluded that this CFD correlation can predict the heat transfer coefficient effectively. It was also observed that by adding nanoparticles to the water it can be enhanced the heat transfer coefficient efficiently. It was also proved that it is possible to predict the heat transfer in nanofluids by novel equations applied in this study
