Forced convection flow and heat transfer of non-newtonian nanofluids through a circular tube

Abstract

Non-Newtonian nanofluids due to either non-Newtonian base fluid or high nano particle concentration flow cases have been numerically investigated through a circular tube under laminar flow condition. Governing equations have been solved in Fluent by utilizing Newtonian and non-Newtonian single-phase and two-phase models. Novel non-Newtonian two-phase modeling methods have been firstly applied in the current thesis. It can be said that two-phase modeling method with Granular model is better than two-phase model without solid phase viscosity from predictive power point of view because it requires less experiments on rheological characteristics. Heat trans fer and pressure drop simulations have been compared with proposed correlations and experimental data in the literature. Heat transfer investigation results revealed that non-Newtonian Eulerian model without solid phase viscosity predicts the heat transfer coefficient better than the other single and two-phase models. Pressure drop simulation results show that non-Newtonian models are better than Newtonian models at pres sure drop prediction of non-Newtonian nanofluids. Error rate decreases with increasing Reynolds number for all numerical modeling methods and single-phase non-Newtonian model gives the most accurate results. Finally, thermal performance of Newtonian and non-Newtonian nanofluids have been investigated in terms of convective heat trans fer coefficient enhancement to pressure drop increment ratio. Thermal performance increases with increasing Reynolds number and decreasing nanoparticle concentration for both Newtonian and non-Newtonian nanofluids. It can be concluded that using a non-Newtonian nanofluid as a working fluid is more efficient than using a Newtonian nanofluid due to high pressure drop rate of Newtonian fluid flow.