Magnetohydrodynamic Flow and Heat Transfer of TiO2-H2O Nanofluid over Nonlinear Stretching Sheet under the Effects of Nanoparticle Diameter

The effects of nanoparticle diameter on the magnetohydrodynamic flow and heat transfer of TiO2-H2O nanofluid over an exponentially stretching sheet are studied in this paper. It is assumed that the effective viscosity of TiO2-H2O nanofluid is a function of nanofluid concentration and nanoparticle diameter by use of new accurate correlation. Therefore, the flow and heat characteristics of TiO2-H2O nanofluid near a surface can be found under the effects of nanoparticle diameter for the first time. For this purpose, the governing partial differential equations are transformed to the nonlinear ordinary differential equations using similarity transformations. The resulting equations are solved analytically using Optimal Homotopy Asymptotic Method (OHAM) which is most applicable in the analysis of nonlinear problems. The effects of nanoparticle diameter, nanofluid concentration, and magnetic field on the flow and heat transfer of nanofluid are investigated in detail. The results show that the reduced skin friction is a descending function of nanoparticle diameter. The reduced Nusselt number is a complicated function of magnetic field, nanofluid concentration, and nanoparticle diameter. It can be found that for the specific values of parameters, the curves of reduced Nusselt number with respect to the parameters such as magnetic field and nanofluid concentration have peaks where the maximum of heat transfer occurs.