Now showing 1 - 3 of 3
  • Placeholder Image
    Publication
    Percolation network dynamicity and sheet dynamics governed viscous behavior of polydispersed graphene nanosheet suspensions
    (01-01-2013)
    Dhar, Purbarun
    ;
    Ansari, Mohammad Hasan Dad
    ;
    Gupta, Soujit Sen
    ;
    Siva, V. Manoj
    ;
    ; ;
    The viscosity of polydispersed graphene nanosheet (5 nm-1.5 μm) suspensions (GNS) and its behavior with temperature and concentration have been experimentally determined. A physical mechanism for the enhanced viscosity over the base fluids has been proposed for the polydispersed GNSs. Experimental data reveal that enhancement of viscosity for GNSs lies in between those of carbon nanotube suspensions (CNTSs) and nano-alumina suspensions, indicating the hybrid mechanism of percolation (like CNTs) and Brownian motion-assisted sheet dynamics (like alumina particles). Sheet dynamics and percolation, along with a proposed percolation network dynamicity factor, have been used to determine a dimensionally consistent analytic model to accurately determine and explain the viscosity of polydispersed GNSs. The model also provides insight into the mechanisms of viscous behavior of different dilute nanoparticle suspensions. The model has been found to be in agreement with the GNS experimental data, and even for CNT (diameter 20 nm, length 10 lm) and nano-alumina (45 nm) suspensions. © Springer Science+Business Media 2013.
  • Placeholder Image
    Publication
    Numerical investigation of natural-convection heat transfer characteristics of Al2O3-water nanofluid flow through porous media embedded in a square cavity
    (01-01-2018)
    Vadri, Siva Sai
    ;
    ;
    In this study, natural-convection heat transfer characteristics of Al2O3-water nanofluid flow through a homogeneous porous medium embedded in a square cavity with several pairs of heaters and coolers located inside are investigated numerically. The two-dimensional equations governing the nanofluid flow and heat transfer through the porous medium are discretized using Streamline Upwind Petrov-Galerkin (SUPG) based Finite Element Method (FEM). The generalized Darcy-Brinkman-Forchheimer's porous medium model is used in this analysis. The average Nusselt number in the cases of the base fluid without a porous medium, of a nanofluid without a porous medium, and a nanofluid with a porous medium are compared for different Rayleigh numbers. It is found that in the case of the nanofluid with a porous medium the highest value of average Nusselt number was obtained. In addition to this, the effect of the Darcy number and the porosity on the pattern of streamlines and isotherms is investigated. It is also observed that the average Nusselt number increases with increasing Darcy number and decreases with increasing porosity and nanoparticle volume fraction.
  • Placeholder Image
    Publication
    Effect of external magnetic field on natural convection in a cubical cavity filled with nano particle suspension.
    (01-01-2018)
    Dixit, Desh Deepak
    ;
    This paper reports experimental investigation of Natural Convection of non-magnetic electrically conducting nano-suspension Multi Wall Carbon Nano Tube (MWCNT) and electrically non-conducting Silica nano-particle suspension, in presence of magnetic field in a differentially heated cubicle cavity with two opposite vertical sides at different constant temperature.The main aim of this experimental investigation is to study the effect of Lorentz force on the heat transfer characteristics of nano-particle suspension, which arises due to motion of nano-particles in applied magnetic field. A comparison between two different particles with different electrical properties is done to establish the effect of Lorentz force on the nano-particles and the effect on heat transfer because of interaction between nano-particles and magnetic field. Experiments are done in a cubicle cavity of 25mm side whose one vertical face is maintained at higher temperature by an electrical heater and other opposite vertical face is maintained at lower temperature using cold bath. The results are compared for 2.5 × 106 to 1 × 107 Rayleigh number range, and different magnetic field strength from 0.00 Tesla to 0.30 Tesla in two different perpendicular directions, to study the effect of strength and direction respectively. A suppression in Nusselt number is observed with increase in magnetic field strength, the suppression is more when the magnetic field lines are perpendicular to the convective flow in MWCNT nano-particle suspension. In presence of magnetic field no suppression is observed in case of silica nano-particle suspension.