Convective heat transfer of non-Newtonian nanofluids through a uniformly heated circular tube

Three kinds of nanofluids were prepared by dispersing γ-Al2O3, CuO, and TiO2 nanoparticles in an aqueous solution of carboxymethyl cellulose (CMC). The forced convective heat transfer of these nanofluids through a uniformly heated circular tube under turbulent flow conditions was investigated experimentally. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Results reveal that the local and average heat transfer coefficients of nanofluids are larger than that of the base fluid. Heat transfer enhancement of nanofluids increases with an increase in nanoparticle concentration. Similar trend are demonstrated for Nusselt number of nanofluids. For a given nanoparticle concentration and Peclet number, the local heat transfer coefficient of the base fluid and that of the nanofluids decreases with the axial distance from the tube inlet. A new correlation is proposed to predict successfully the Nusselt number of non-Newtonian nanofluids as a function of the Reynolds and the Prandtl numbers.