In this study,magneto-hydrodynamics (MHD) mixed convection effects of Al2O3-water nanofluid flow over a backward-facing step were investigated numerically for various electrical conductivity models of nanofluids.A uni...In this study,magneto-hydrodynamics (MHD) mixed convection effects of Al2O3-water nanofluid flow over a backward-facing step were investigated numerically for various electrical conductivity models of nanofluids.A uniform external magnetic field was applied to the flow and strength of magnetic field was varied with different values of dimensionless parameter Hartmann number (Ha=0,10,20,30,40).Three different electrical conductivity models were used to see the effects of MHD nanofluid flow.Besides,five different inclination angles between 0°-90° is used for the external magnetic field.The problem geometry is a backward-facing step which is used in many engineering applications where flow separation and reattachment phenomenon occurs.Mixed type convective heat transfer of backward-facing step was examined with various values of Richardson number (Ri=0.01,0.1,1,10) and four different nanoparticle volume fractions (Ф=0.01,0.015,0.020,0.025) considering different electrical conductivity models.Finite element method via commercial code COMSOL was used for computations.Results indicate that the addition of nanoparticles enhanced heat transfer significantly.Also increasing magnetic field strength and inclination angle increased heat transfer rate.Effects of different electrical conductivity models were also investigated and it was observed that they have significant effects on the fluid flow and heat transfer characteristics in the presence of magnetic field.展开更多
Properties and microstructure of mixed reverse micelles of anionic surfactant AOT and nonionic surfactants in n-heptane were investigated using conductivity, fluorescence probe,and dynamic light scattering. As in the ...Properties and microstructure of mixed reverse micelles of anionic surfactant AOT and nonionic surfactants in n-heptane were investigated using conductivity, fluorescence probe,and dynamic light scattering. As in the reverse micelle formed with AOT alone, a conductivity maximum was also observed in conductivity-W,(molar ratio of water to surfactants) curves for mixed reverse micellar systems, and W0,mex (W, at the conductivity maximum) moves to a smaller value with the increase of nonionic surfactants contents and their EO chain length. This phenomenon was interpreted in terms of the results of dynamic light scattering and the microstructure of the mixed reverse micelles. The fluorescent behaviour of fluorescence probe Ru(bPy)2+ in mixed reverse micelles indicates that W0, at which the hydration of head groups of surfactants finished, decreases with the increase of nonionic surfactants contents, but increases with their EO chain length at a constant ratio of nonionic surfactants to AOT.展开更多
文摘In this study,magneto-hydrodynamics (MHD) mixed convection effects of Al2O3-water nanofluid flow over a backward-facing step were investigated numerically for various electrical conductivity models of nanofluids.A uniform external magnetic field was applied to the flow and strength of magnetic field was varied with different values of dimensionless parameter Hartmann number (Ha=0,10,20,30,40).Three different electrical conductivity models were used to see the effects of MHD nanofluid flow.Besides,five different inclination angles between 0°-90° is used for the external magnetic field.The problem geometry is a backward-facing step which is used in many engineering applications where flow separation and reattachment phenomenon occurs.Mixed type convective heat transfer of backward-facing step was examined with various values of Richardson number (Ri=0.01,0.1,1,10) and four different nanoparticle volume fractions (Ф=0.01,0.015,0.020,0.025) considering different electrical conductivity models.Finite element method via commercial code COMSOL was used for computations.Results indicate that the addition of nanoparticles enhanced heat transfer significantly.Also increasing magnetic field strength and inclination angle increased heat transfer rate.Effects of different electrical conductivity models were also investigated and it was observed that they have significant effects on the fluid flow and heat transfer characteristics in the presence of magnetic field.
文摘Properties and microstructure of mixed reverse micelles of anionic surfactant AOT and nonionic surfactants in n-heptane were investigated using conductivity, fluorescence probe,and dynamic light scattering. As in the reverse micelle formed with AOT alone, a conductivity maximum was also observed in conductivity-W,(molar ratio of water to surfactants) curves for mixed reverse micellar systems, and W0,mex (W, at the conductivity maximum) moves to a smaller value with the increase of nonionic surfactants contents and their EO chain length. This phenomenon was interpreted in terms of the results of dynamic light scattering and the microstructure of the mixed reverse micelles. The fluorescent behaviour of fluorescence probe Ru(bPy)2+ in mixed reverse micelles indicates that W0, at which the hydration of head groups of surfactants finished, decreases with the increase of nonionic surfactants contents, but increases with their EO chain length at a constant ratio of nonionic surfactants to AOT.
