Search

In this article, frictional pressure drop of non-Newtonian nanofluids flowing through a horizontal circular tube was investigated experimentally in both the laminar and the turbulent regimes. Three different types of oxide nanoparticles, γ-Al2O3, CuO, and TiO2, were used for the preparation of nanofluids. A 0.5 wt% aqueous solution of carboxymethyl cellulose (CMC) was used as the base fluid. Pressure drop were measured for a wide range of nanoparticle concentrations. The dimensionless pressure drop for all nanofluids in both the laminar and the turbulent flow regimes as a function of the Reynolds number follows the same trend of the pressure drop observed with the base fluid. Results presented in this investigation are significant because better heat transfer coefficients prevail for nanofluids and yet without an increase in the pressure drop. [ABSTRACT FROM AUTHOR]

Fluids in which nanometer-sized solid particles are suspended are called nanofluids. These fluids can be employed to increase the heat transfer rate in various applications. In this study, the convective heat transfer for Cu/water nanofluid through a circular tube was experimentally investigated. The flow was laminar, and constant wall temperature was used as thermal boundary condition. The Nusselt number of nanofluids for different nanoparticle concentrations, as well as various Peclet numbers, was obtained. Also, the rheological properties of the nanofluid for different volume fractions of nanoparticles were measured and compared with theoretical models. The results show that the heat transfer coefficient is enhanced by increasing the nanoparticle concentrations as well as the Peclet number. [ABSTRACT FROM AUTHOR]

Abstract: The Reiner–Rivlin viscoelastic model was used to investigate numerically on the pattern and strength of the secondary flows in rounded corners square ducts. The influence of rheological properties on flow domain was studied. The governing equations for steady state, laminar fully developed flow were solved by finite difference method. It is shown the secondary flow of a Reiner–Rivlin fluid has a negligible effect on the axial flow and f.Re. Viscous and elastic behaviors as well as the rounding of the corners have important effects on the secondary flows created by viscoelastic fluid. [Copyright &y& Elsevier]

Forced convection heat transfer to a fully developed laminar flow of simplified Phan-Thien-Tonner fluid in an annulus was studied analytically. Inner and outer cylinders were stationary and subjected to constant heat flux. The results of the velocity and temperature distributions, dimensionless pressure gradient, and Nusselt number were obtained for a wide range of aspect ratios and dimensionless viscoelastic groups. Results indicated the gap between two cylinders as well as viscoelastic behavior of the fluid have noticeable effects on flow and heat transfer [ABSTRACT FROM AUTHOR]

Abstract: Nanofluids are suspensions of metallic or nonmetallic nanopowders in base liquid and can be employed to increase heat transfer rate in various applications. In this work laminar flow forced convection heat transfer of Al2O3/water nanofluid inside a circular tube with constant wall temperature was investigated experimentally. The Nusselt numbers of nanofluids were obtained for different nanoparticle concentrations as well as various Peclet and Reynolds numbers. Experimental results emphasize the enhancement of heat transfer due to the nanoparticles presence in the fluid. Heat transfer coefficient increases by increasing the concentration of nanoparticles in nanofluid. The increase in heat transfer coefficient due to presence of nanoparticles is much higher than the prediction of single phase heat transfer correlation used with nanofluid properties. [Copyright &y& Elsevier]