Radiative heat transfer in MHD mixed convection flow of nanofluids along a vertical channel

Over the past few decades, nanofluids have emerged as a promising technology for the enhancement of the intrinsic thermophysical properties of many convectional heat transfer fluids such as water and oil. Many researchers have been investigated the merits of dispersing nanometer-sized particles into base fluids to enhance heat transfer, thermal conductivity and viscosity of the fluids. Therefore, this research focused on radiative heat transfer in magnethohydrodynamics mixed convection flow in a channel filled with nanofluids containing different type of nanoparticles. Five types of nanoparticles (Al2O3, 3 4Fe O , Cu, 2 TiO , and Ag) with five different shapes (platelet, blade, cylinder, brick and spherical) were used in water 2 (H O) and ethylene glycol 2 6 2 (C H O), as conventional base fluid. An important subtype of nanofluids called ferrofluids 3 4 (Fe O in water based nanofluids) was also studied. Four different problems were modelled as partial differential equations with physical boundary conditions. In the first three problems, the channel walls were taken rigid, while the fourth problem the walls were chosen permeable where suction or injection was taking place. Perturbed type analytical solutions for velocity and temperature were obtained and discussed graphically in various graphs. Results for skin friction and Nusselt number were also computed and presented in tabular forms. This study showed that 2 6 2 C H O was the better convectional base fluid compared to 2 H O because of the higher viscosity and thermal conductivity. Ag nanoparticles had the highest thermal conductivity and viscosity compared to other type of nanoparticles. Increasing nanoparticles size had caused variation in velocity. It was also observed that, variation in velocity for Ag nanoparticles was obtained at low volume concentration, whereas for 2 3 Al O nanoparticles, this variation was observed only at high volume concentration. Velocity increases with increasing Grashof number, radiation, heat generation and permeability parameters, but decreases with increasing magnetic parameter and volume fraction of nanoparticles. However, the effects of these parameters were quite different in the case of suction and injection. Results had also shown that, temperature increases with increasing radiation and heat generation parameters. In this study, the temperature of ferrofluids was found smaller when compared to the temperature of nanofluids

Radiation and heat generation effects in magnetohydrodynamic mixed convection flow of nanofluids

Radiation and heat generation effects in unsteady magnetohydrodynamic mixed convection flow of nanofluids along a vertical channel are investigated. Silver nanoparticles of spherical shapes and of different sizes in water as a convection-al base fluid are incorporated. The purpose of this study is to measure the effect of different sizes of nanoparticles on velocity and temperature. Keeping in mind the size, particle material, shape, clustering and Brownian motion of nanoparti-cles, Koo and Kleinstreuer model is used. The problem is modeled in terms of partial differential equations with physical boundary conditions. Analytical solu-tions are obtained for velocity and temperature, plotted and discussed. It is con-cluded that increasing the size of Ag nanoparticles (up to specific size, 30 nm, re-sults in a very small velocity increment while for large particle size (30-100 nm), no change in velocity is observed. As the small size of nanoparticles has the high-est thermal conductivity and viscosity. This change in velocity with size of nano-particles is found only in water-based nanofluids with low volume fraction 0.01 while at low volume concentration, no change is observed

Energy Transfer in Mixed Convection MHD Flow of Nanofluid Containing Different Shapes of Nanoparticles in a Channel Filled with Saturated Porous Medium

Energy transfer in mixed convection unsteady magnetohydrodynamic (MHD) flow of an incompressible nanofluid inside a channel filled with a saturated porous medium is investigated. The walls of the channel are kept at constant temperature, and uniform magnetic field is applied perpendicular to the direction of the flow. Three different flow situations are discussed on the basis of physical boundary conditions. The problem is first written in terms of partial differential equations (PDEs), then reduces to ordinary differential equations (ODEs) by using a perturbation technique and solved for solutions of velocity and temperature. Four different shapes of nanoparticles inside ethylene glycol (C2H6O2) and water (H2O)‐based nanofluids are used in equal volume fraction. The solutions of velocity and temperature are plotted graphically, and the physical behavior of the problem is discussed for different flow parameters. It is evaluated from this problem that viscosity and thermal conductivity are the dominant parameters responsible for different consequences of motion and temperature of nanofluids. Due to greater viscosity and thermal conductivity, C2H6O2‐based nanofluid is regarded as better convectional base fluid assimilated to H2O

Unsteady flow of a second grade fluid between two oscillating vertical plates

This article deals with the study of unsteady flow of a second grade fluid between two oscillating vertical plates. Three different flow situations are discussed. The problem is modeled in terms of non-linear partial differential equation with some physical conditions. Exact analytic solutions are obtained by using the Optimal Homotopy Asymptotic Method (OHAM).This method is frequently used for solving non-linear differential equations arise in various applied sciences and is found quite useful. The physical influence of various parameters on velocity is studied graphically and discussed

Entropy generation in a mixed convection Poiseulle flow of molybdenum disulphide Jeffrey nanofluid

Entropy analysis in a mixed convection Poiseulle flow of a Molybdenum Disulphide Jeffrey Nanofluid (MDJN) is presented. Mixed convection is caused due to buoyancy force and external pressure gradient. The problem is formulated in terms of a boundary value problem for a system of partial differential equations. An analytical solution for the velocity and the temperature is obtained using the perturbation technique. Entropy generation has been derived as a function of the velocity and temperature gradients. The solutions are displayed graphically and the relevant importance of the input parameters is discussed. A Jeffrey nanofluid (JN) has been compared with a second grade nanofluid (SGN) and Newtonian nanofluid (NN). It is found that the entropy generation decreases when the temperature increases whereas increasing the Brickman number increases entropy generation. Keywords: MoS2 nanoparticles, Mixed convection, Channel flow, Entropy generation, Heat transfer, MoS2 Jeffrey nanofluid

Heat transfer in MHD mixed convection flow of a ferrofluid along a vertical channel

This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published wor

Velocity graph for <i>N</i> = 0.1, 0.9, 1.2, 1.4 when <i>Gr</i> = 0.1, <i>φ</i> = 0.04, Re = 1, <i>Pe</i> = 1, <i>M</i> = 1, <i>λ</i> = 1, <i>τ</i> = 5 and <i>ω</i> = 0.2.

<p>Velocity graph for <i>N</i> = 0.1, 0.9, 1.2, 1.4 when <i>Gr</i> = 0.1, <i>φ</i> = 0.04, Re = 1, <i>Pe</i> = 1, <i>M</i> = 1, <i>λ</i> = 1, <i>τ</i> = 5 and <i>ω</i> = 0.2.</p

Thermophysical properties of base fluid (water) and nanoparticles (iron oxide and alumina oxide).

<p>Thermophysical properties of base fluid (water) and nanoparticles (iron oxide and alumina oxide).</p

Temperature graph for <i>φ</i> when <i>N</i> = 1.5 and <i>τ</i> = 0.5.

<p>Temperature graph for <i>φ</i> when <i>N</i> = 1.5 and <i>τ</i> = 0.5.</p