MHD Mixed Convective Heat Transfer Research Articles

Expression of Concern: Entropy analysis and MHD mixed convection heat transfer of the magnetic nanofluid in an asymmetric T-shaped cavity using the lattice Boltzmann method

Expression of Concern: Entropy analysis and MHD mixed convection heat transfer of the magnetic nanofluid in an asymmetric T-shaped cavity using the lattice Boltzmann method

MHD Mixed Convection of Developing Slip Flow in a Vertical Porous Microchannel Under Local Thermal Non–Equilibrium Conditions

ABSTRACT MHD mixed convection heat transfer of an ionized gas in a vertical microchannel filled with a porous medium is simulated and discussed in this study. The considered flow is hydrodynamically and thermally developing with Local Thermal Non – Equilibrium (LTNE) between the gas and the solid matrix. The Darcy – Brinkman – Forchheimer model is utilized to describe the flow filed in the porous medium. Moreover, both velocity – slip and temperature – jump boundary conditions are applied to the gas at the walls. The governing equations are solved by the finite – volume method. Results are presented and discussed in terms of the developed profiles of velocity and temperature of the constituents as well as the variations of the Nusselt number through the microchannel, the numerical values of the hydrodynamic and thermal entry lengths, and the fully – developed Nusselt number for different conditions. It is found that direct relations exist between the fully – developed Nusselt number and the Richardson number, the Reynolds number, the Hartmann number, the Biot number, the thermal conductivity ratio, and the Forchheimer number. With rise in the Knudsen number or the Darcy number, however, the Nusselt number deteriorates. The results indicate that the Knudsen number, the Hartmann number, the Biot number, and the thermal conductivity ratio are the most influential parameters on the fully – developed Nusselt number. It is envisaged that a tenfold increase in the Hartmann number and a hundredfold elevation in the Knudsen number are accompanied by 14% rise and 42% reduction in the fully – developed Nusselt number, respectively.

MHD Mixed Convective Non-Newtonian Stagnation Point Flow Over an Inclined Stretching Sheet: Numerical Simulation

This paper includes numerical simulation upon MHD mixed convective heat transfer properties of stagnation point flow across an angled stretched sheet. Boundary value problem is solved using similarity transformation approach with shooting technique. The impact of different corporeal constraints like mixed convection parameter, thermal radiation parameter, chemical reaction parameter, Brownian motion and thermophoresis, Casson parameter upon velocity and temp profile as well as skin-friction coefficient , Nusselt number, Sherwood number on velocity, temp concentration profile are shown graphically. Casson parameter increases velocity and diminishes temperature profile. Chemical reaction term decreases Sherwood number and increases concentration profile.

MHD mixed convection heat transfer of nanofluid containing oxytactic microorganisms inside a vertical annular porous cylinder

For the first time, MHD mixed convection heat transfer of nanofluid containing oxytactic microorganisms is investigated inside a vertical annular porous cylinder. In this work, governing equations presented by Kuznetsov concerning the nanofluid flow inside porous media in the presence of microorganisms are initially extended for the case of cylindrical coordinates, and then numerically solved using the FVM approach. Having conducted a comparison with previous studies, the numerical method's accuracy has been successfully validated. The simulations are undertaken for different parameters including bioconvection Rayleigh number, Hartmann number, product of Reynolds and Prandtl numbers, bioconvection Peclet number, traditional and bioconvection Lewis numbers, aspect ratio, and radius ratio for the case of horizontal magnetic field exertion. Obtained results are presented in terms of graphical streamlines, isothermal lines, isoconcentration of nanoparticles, oxygen, and microorganisms as well as physical quantities of interest. Based on outcomes, it is concluded that microorganisms’ presence results in heat transfer attenuation, while an increase in the Hartmann number leads to the average Nusselt number amelioration.

Effects of magnetic field inclination and internal heat sources on nanofluid heat transfer and entropy generation in a double lid driven L-shaped cavity

Mixed convection has been one of the most interesting subjects of study in the area of heat transfer for many years. The entropy generation due to MHD mixed convection heat transfer in L-shaped enclosure being filled with Cu-water nanofluid and having an internal heating generation is explored in this investigation by the finite volume technique. Lid-motion is presented by both right and top parts of walls to induce forced convection and the cavity is under an inclined uniform magnetic field along the positive horizontal direction. The statistics concentrated specifically on the impacts of several key parameters like as the aspect ratio of the enclosure, Hartmann number, nanoparticle volume fraction, and heat source length/location on the heat transfer inside the L-shaped enclosure. Outcomes have been manifested in terms of isotherm lines, streamlines, local and average Nusselt numbers. The obtained results show that addition of nanoparticles into pure fluid leads to increase of heat transfer. The maximum value of local Nusselt pertaining to the heat source occurs when L = 0.1. Impacts of heat source size and location, internal heat generation absorption, angle of magnetic field on heat transfer and entropy generation are completely analyzed and discussed. The best configuration and values of important parameters are also presented using thermal performance criteria.

Effect of magnetohydrodynamics on heat transfer intensification and entropy generation of nanofluid flow inside two interacting open rectangular cavities

MHD mixed convection heat transfer and entropy generation analysis for Cu–water nanofluid inside two interacting open cavities are numerically investigated. The right and the left walls of each cavity are heated or cooled at uniform but different heat flux densities. The nanofluid flow is described by the Buongiorno model in order to take into account the thermophoresis effect and the Brownian motion. The governing equations are solved using the finite volume method with the SIMPLE algorithm. The effects of relevant parameters including the Hartmann number (Ha), the Richardson number (Ri), the opening ratio (R), the heat flux ratio (Rq) and the nanoparticles volume fraction (ϕi) are analyzed. The results show that the flow pattern resulting from the simultaneous action of the magnetic field and the buoyancy force is heightened by the decrease in Ha and R and the increase in Ri and Rq. The heat transfer, which evolves in a non-monotonous way with the Hartmann number, is enhanced by the rise of the Richardson number, the heat flux ratio and the nanoparticles volume fraction, as well as by the reduction in the opening ratio. It is also observed that, overall, the thermodynamic disorder is dominated by the thermal irreversibility which decreases at high Ha with the augmentations of Ri and ϕi and the reductions in R and Rq.

Effects of two-phase nanofluid model on convection in a double lid-driven cavity in the presence of a magnetic field

Purpose The aim of this study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments. Design/methodology/approach The current work investigates the problem of mixed convection heat transfer in a double lid-driven square cavity in the presence of magnetic field. The used cavity is filled with water-Al2O3 nanofluid based on Buongiorno’s two-phase model. The bottom horizontal wall is maintained at a constant high temperature and moves to the left/right, while the top horizontal wall is maintained at a constant low temperature and moves to the right/left. The left and right vertical walls are thermally insulated. The dimensionless governing equations are solved numerically using the Galerkin weighted residual finite element method. Findings The obtained results show that the heat transfer rate enhances with an increment of Reynolds number or a reduction of Hartmann number. In addition, effects of thermophoresis and Brownian motion play a significant role in the growth of convection heat transfer. Originality/value According to above-mentioned studies and to the authors’ best knowledge, there has no study reported the MHD mixed convection heat transfer in a double lid-driven cavity using the two-phase nanofluid model. Thus, the authors of the present study believe that this work is valuable. Therefore, the aim of this comprehensive numerical study is to investigate the effects of two-phase nanofluid model on mixed convection in a double lid-driven square cavity in the presence of a magnetic field. The authors believe that this work is a good contribution for improving the thermal performance and the heat transfer enhancement in some engineering instruments.

Second law analysis of MHD mixed convection heat transfer in a vented irregular cavity filled with Ag–MgO/water hybrid nanofluid

The present paper investigates numerically the effect of an external magnetic field on heat transfer and entropy generation of Ag–MgO (50:50 vol%)/water hybrid nanofluid flow in a partially heated irregular ventilated cavity. A finite-volume FORTRAN code has been written to solve the governing partial differential equations. New empirical correlations specifically dedicated to predict the dynamic viscosity and the thermal conductivity of the considered hybrid nanofluid were employed. After validation of model, the analysis has been done for a wide range of Reynolds number (10 ≼ Re ≼ 600), Hartmann number (0 ≼ Ha ≼ 80) and total nanoparticle volume fraction (0 ≼ φ ≼ 0.02). The results are presented in terms of streamlines, isotherms and isentropic lines as well as the average Nusselt number (Num), the average entropy generation (Sgen,m) and the Bejan number (Beavg). The criterion ξ = Sgen,m/Num is adopted to discuss the thermal performances of the system. The results reveal that the intensification of the magnetic field tends to attenuate the heat transfer convection and to reduce the thickness of the thermal boundary layer, close to the active walls. Globally, adding nanoparticles to the base fluid improves the heat transfer but increases the total entropy generation.

MHD mixed convective heat transfer in a lid-driven enclosure filled with Ag-water nanofluid with center heater

The MHD mixed convection inside enclosure with center heater is numerically investigated. The oppositely moving side walls of the enclosure are maintained at constant cold temperature whereas a constant heat source is considered in the bottom wall. The remaining parts of the bottom and top walls are kept adiabatic. The finite volume method and SIMPLE algorithm with power-law scheme is used to solve the governing equations. The present study is concerned with effect of pertinent parameters such as length of heater (Γ = 0.25, 0.50 and 0.75), Richardson number (Ri = 0.01, 1.0 and 100), Hartmann number (Ha = 0, 25 and 50) and solid volume fraction of nanoparticles on the fluid flow and heat transfer performance of the enclosure. Results are presented with streamlines, isotherms, velocity profiles and average Nusselt numbers. It is observed that heat transfer rate increases as heater length and Grashof number increases whereas heat transfer decrease is found for increasing magnetic field effect. The enhancement rate in heat transfer by increasing the solid volume fraction of nanoparticles is also obtained.

Thermal and hydrodynamic performances of MHD ferrofluid flow inside a porous channel

MHD mixed convection heat transfer inside a rectangular porous channel under the effects of constant and alternating magnetic fields has been experimentally investigated. Deionized water containing magnetite particles flows through the channel filled with copper foam as a porous media. A constant heat flux condition is imposed on the top and bottom plates of the channel, while the side walls are adiabatic. Experiments were carried out at Gr=7.31×106 and 373≤Re≤1186. Influence of porous media, volume fraction of ferrofluid (ϕ=0.5%, 1%, 1.5%), Reynolds number and magnetic field intensities and frequencies (B=250, 450G and f=5, 10Hz) on the characteristics of heat transfer and hydrodynamic are studied. The experimental results revealed that the copper foam has a significant effect on the thermal and hydrodynamic performances of the channel due to heat spreading through the copper matrix, better mixing of the fluid and extending the heat transfer area. It was observed that employing ferrofluid with different volume fractions increases both heat transfer rate and pressure drop because of thermal conductivity and viscosity increment, respectively. Applying constant magnetic field causes aggregation of nanoparticles in the area where the magnetic field is applied and consequently, heat transfer and pressure drop increase. Moreover employing alternating magnetic field further increased the heat transfer rate due to more intensified disturbance of the thermal boundary layer and improvement of the nanoparticles migrations. The alternating magnetic field reduced pressure drop because of the periodic magnetic forces, leading to enhanced overall performance of the channel.

MHD mixed convection heat transfer over a non-linear slender elastic sheet with variable fluid properties

MHD mixed convection heat transfer over a non-linear slender elastic sheet with variable fluid properties

MHD mixed convection heat transfer over a non-linear slender elastic sheet with variable fluid properties

Abstract An analysis is presented for mixed convection and heat transfer in a viscous electrically conducting fluid flow at an impermeable stretching vertical sheet with variable thickness. The nonlinear equations that describe the fluid flow, and heat transfer processes have been solved using the Keller-box method. A limited parametric study is undertaken to determine the sensitivity and changes in the flow and temperature fields with respect to variations in the buoyancy parameter, the temperature dependent viscosity and thermal conductivity parameters, the plate velocity power index, and the Prandtl number which are presented in graphical and tabulated formats. To validate the results, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The effects of embedded parameters on the dimensionless velocity profiles and temperature are examined through graphs. The variation of Local Nusselt number is also analysed. One of the important findings of our study is that the velocity distribution at a point near the plate decreases as the wall thickness parameter increases and hence the thickness of the boundary layer becomes thinner when m < 1. Further, the effect of the magnetic field is to reduce the fluid velocity and to increase the temperature field.

Unsteady MHD Mixed Convection inside L-shaped Enclosure in the Presence of Ferrofluid (Fe3O4)

Mixed convection has been one of the most interesting topics of research in the field of heat transfer for many years. In the present study, unsteady MHD mixed convection heat transfer inside a heated L-shaped enclosure filled with Fe3O4water has been investigated numerically. Lid-motion is introduced by the top wall to induce forced convection. For pure mixed convection (Ri = 1), Grashof number (Gr = 103 - 105) and time (τ) are varied, whereas the solid volume fraction of nanofluid (φ = 0.1) and Hartman number (Ha = 25) are kept constant. Results have been presented in terms of isotherm lines, streamlines, average Nusselt (Nu) number and average temperature (θay). The obtained results show that MHD causes significant effects on heat transfer rate. Interestingly, natural convection is more effective in this case of mixed convection as higher values of Nu are obtained for higher values of Gr.

Conjugate-MHD mixed convection from a vertical flat plate in presence of viscous dissipation

The present article investigates MHD-mixed convection heat transfer about a thin vertical plate in the presence of viscous dissipation and wall conduction (i.e. conjugate) heat transfer effects. The fluid is assumed to be incompressible and dense. The Keller box method, an implicit finite difference method, is used in the solution of the nonlinear boundary layer equations, following their transformation into the non-similar ordinary equations. Comprehensive parametric tests are conducted to determine the effects of the mixed convection parameter Ri, the magnetic parameter Mn and viscous dissipation parameter Ec on the local skin friction and local heat transfer are presented graphically and analyzed.

Mixed Convective Heat Transfer for MHD Viscoelastic Fluid Flow over a Porous Wedge with Thermal Radiation

The main concern of the present paper is to study the MHD mixed convective heat transfer for an incompressible, laminar, and electrically conducting viscoelastic fluid flow past a permeable wedge with thermal radiation via a semianalytical/numerical method, called Homotopy Analysis Method (HAM). The boundary-layer governing partial differential equations (PDEs) are transformed into highly nonlinear coupled ordinary differential equations (ODEs) consisting of the momentum and energy equations using similarity solution. The current HAM solution demonstrates very good agreement with previously published studies for some special cases. The effects of different physical flow parameters such as wedge angle (β), magnetic field ( M), viscoelastic ( k1), suction/injection ( fw), thermal radiation ( Nr), and Prandtl number (Pr) on the fluid velocity component ( f′( η)) and temperature distribution ( θ( η)) are illustrated graphically and discussed in detail.

MHD mixed convective heat transfer over a permeable stretching wedge with thermal radiation and ohmic heating

In this paper, a new analytical method named DTM-BF is proposed and applied to study the MHD mixed convective flow and heat transfer of an incompressible, viscous and electrically conducting fluid over a stretching permeable wedge in the presence of thermal radiation and ohmic heating. The boundary layer governing equations of PDES are transformed into highly nonlinear coupled ODES and the approximate solutions are derived by the new proposed analytical technique—the differential transformation and basis functions method (DTM-BF) on unbounded domains. The effects of the velocity ratio parameter, magnetic field parameter, the wedge angle parameter, the mixed convection parameter, suction/injection parameter, thermal radiation parameter, Eckert number and Prandtl number are presented. Moreover, the reliability and effectiveness of the DTM-BF have been verified by comparing analytical results with numerical solutions. Some new characteristics of the mixed convective flow and heat transfer over a wedge are investigated and discussed.

MHD mixed convective heat transfer flow about an inclined plate

Mixed convection heat transfer about a semi-infinite inclined plate in the presence of magneto and thermal radiation effects is studied. The fluid is assumed to be incompressible and dense. The nonlinear coupled parabolic partial differential equations governing the flow are transformed into the non-similar boundary layer equations, which are then solved numerically using the Keller box method. The effects of the mixed convection parameter Ri, the angle of inclination α, the magnetic parameter M and the radiation–conduction parameter Rd on the velocity and temperature profiles as well as on the local skin friction and local heat transfer parameters. For some specific values of the governing parameters, the results are compared with those available in the literature and a fairly good agreement is obtained.

Effect of variable viscosity on MHD non-Darcy mixed convective heat transfer over a stretching sheet embedded in a porous medium with non-uniform heat source/sink

Abstract An analysis has been presented to investigate the effect of temperature-dependent viscosity on non-Darcy MHD mixed convective heat transfer past a porous medium by taking into account of Ohmic dissipation and non-uniform heat source/sink. Thermal boundary layer equation takes into account of viscous dissipation and Ohmic dissipation due to transverse magnetic field and electric field. The governing fundamental equations are first transformed into system of ordinary differential equations using self-similarity transformation and are solved numerically by using the fifth-order Runge–Kutta–Fehlberg method with shooting technique for various values of the physical parameters. The effects of variable viscosity, porosity, Eckert number, Prandtl number, magnetic field, electric field and non-uniform heat source/sink parameters on velocity and temperature profiles are analyzed and discussed. Favorable comparisons with previously published work on various special cases of the problem are obtained. Numerical results on the development of the local skin-friction co-efficient and local Nusselt number with non-uniform heat source/sink are tabulated for various physical parameters to show the interesting aspects of the solution.