Magnetohydrodynamic Natural Convection Research Articles

Transient performance analysis of a novel design of portable magnetic refrigeration system.

The widely used ice chamber-based cold storage for the transportation and storage of vaccines has several disadvantages, including uncontrolled overall temperature, water accumulation, and frequent ice pack renewal. Therefore, in this work, we numerically studied a novel vaccine storage system by coupling magnetic refrigeration and ice packs developed by conserving the advantages of an ice-based system. A two-dimensional numerical model is developed to analyze the magnetohydrodynamic natural convection in the storage chamber. Gadolinium of 0.08 kg is used to produce a cooling power of 31.514 W and a coefficient of performance of 1.3. With the constant heat leaked of 0.828 W into the system with dimensions of (0.1 × 0.1) m, the average life of the ice pack of 0.75 kg is 1.03 h. By introducing the magnetocaloric effect, the life of the same ice pack can be infinite with no load. The dynamic mode decomposition analysis reveals that the most dominant fluid interaction occurs between the cooled gadolinium plate and the adjacent fluid, resulting in efficient cooling of the air chamber. The developed vaccine chamber design will significantly improve the existing ice pack system with a nominal increase in cost and system weight.

Finite Element Analysis of Magnetohydrodynamic Natural Convection within Semi-Circular Top Enclosure with Triangular Obstacles

The phenomena of magneto-hydrodynamic natural convection in a two-dimensional semicircular top enclosure with triangular obstacle in the rectangular cavity were studied numerically. The governing differential equations are solved by using the most important method which is finite element method (weighted-residual method). The top wall is placed at cold Tc and bottom wall is heated Th. Here the sidewalls of the cavity assumed adiabatic. Also all the wall are occupied to be no-slip condition. A heated triangular obstacle is located at the center of the cavity. The study accomplished for Prandtl number Pr = 0.71; the Rayleigh number Ra = 103, 105, 5 × 105, 106 and for Hartmann number Ha = 0, 20, 50, 100. The results represent the streamlines, isotherms, velocity and temperature fields as well as local Nusselt number.

Magnetohydrodynamic Natural Convection of In-Ga-Sn Alloy in a Horizontal Concentric Annulus with Tree-Shaped Internal Fins

Magnetohydrodynamic Natural Convection of In-Ga-Sn Alloy in a Horizontal Concentric Annulus with Tree-Shaped Internal Fins

Double Diffusive Magnetohydrodynamic (MHD) Natural Convection and Entropy Generation in a Discretely Heated Inclined Dome-Shaped Enclosure Filled with Cu-Water Nanofluid

This research presents an investigation of laminar two-dimensional double-diffusive free convection and entropy formation in an inclined enclosure under the influence of an inclined magnetic field. The performance of natural convective heat transfer can be improved by doing modifications in enclosure geometry that impact the flow structure. We have considered a dome-shaped enclosure to examine the heat and mass transfer performance. The enclosure is saturated with Cu-water nanofluid and the two sidewalls of the enclosure are maintained at constant temperature Tc(<Th) and concentration cc(<ch). The top-curved wall is adiabatic, and the lower wall is discretely heated and concentrated. The governing equations are first non-dimensionalized and then written in stream function-velocity formulation that is solved numerically using the Bi-CGStab method. A comparison with previously published work in literature is presented and found to be in excellent agreement. Numerical simulations are performed for various values of considered parameters such as Rayleigh number (Ra), Hartmann number (Ha), the orientation of magnetic field (γ), volume fraction of nanoparticles (Φ), and inclination angle of the enclosure (δ). The mentioned parameters have a substantial impact on the cavity flow characteristics. The obtained results demonstrate that the average Sherwood number and Nusselt number are decreasing functions of both the Hartmann number and inclination angle of the enclosure. The minimum heat and mass transfer took place at δ = 135° as the angle of inclination of the enclosure restrains the fluid velocity and reduces the heat transfer rate. Also, entropy generation analysis is conducted for all the considered parameters. The results show that the dome-shaped enclosure has a substantial impact on the fluid flow that enables a smoother and more effective flow inside the cavity, which improves the natural convective heat and mass transmission.

Induced magnetic field effect on MHD free convection flow in nonconducting and conducting vertical microchannel walls

AbstractThe current examination employs a numerical analysis to ascertain the effect of the Eckert number along with the Prandtl number on a magnetohydrodynamic natural convection flow of an incompressible viscous fluid in which it is electrically conducting, passing through a perpendicular microchannel. Conduction along with non‐conducting immeasurable perpendicular walls within the existence of temperature and velocity slip at the microchannel is analyzed. The induced magnetic field (IMF) generated by the motion of an electrically conducting fluid in the presence of a transverse magnetic field is considered. The momentum and induction equations are coupled in the presence of an induced magnetic field. A set of similar variables are used to convert the governing set of equations to nonlinear‐coupled ordinary differential equations. With the aid of MATLAB in built solver is carried out to get the numerical solutions. The influences of Hartman number, Prandtl number, and Eckert number along with some physical parameters are explained through graphs. The results indicate that increasing the Hartmann and magnetic Prandtl numbers results in a significant decrease in volume flow rate.

Numerical analysis of magnetohydrodynamic natural convection in a nanofluid filled quadrantal enclosure

The present numerical work investigates the magnetohydrodynamic buoyancy driven thermal energy transport inside a copper-water nanofluid filled quadrantal enclosure. The base of the enclosure is subjected to constant temperature heating, while the vertical wall is maintained at a uniform cold temperature and the curved wall is insulated. The results are enumerated for the following range of parameters: 103 ≤ Rayleigh number (Ra) ≤ 106, 0 ≤ Hartmann number (Ha) ≤ 100 and 0 ≤ volume fraction of nanoparticles (ϕ) ≤ 0.05. It reveals that the average Nusselt number is a function of ϕ and it shows an increase with ϕ. Further, it is also observed that the average Nusselt number decreases with Ha and the change is more profound at higher Ra (105 and 106) values. The heat transfer rate is increased by decreasing the sector angle of enclosure and vice versa. In this way not only Ra, ϕ, Ha influence the heat transfer rate but a geometry variation has an equal role to play in the alteration of heat transfer.

Thermal performance analysis of hybrid nanofluid natural convection in a square cavity containing an elliptical obstacle under variable magnetic field

PurposeThis study aims to analyze entropy generation and magnetohydrodynamic (MHD) natural convection of hybrid nanofluid in a square cavity, with a heated elliptical block placed at the center, in presence of a periodic-variable magnetic field.Design/methodology/approachIn this paper, simulations were performed with a FORTRAN home code. The numerical methodology used to solve Navier–Stokes, energy and entropy generation equations with corresponding boundary conditions, is essentially based on the finite volume method and full multigrid acceleration.FindingsThe cavity is filled with Ag–Tio2/Water hybrid nanofluid. The main objective of this investigation is to predict the effects of body’s size (6 cases), type of applied magnetic field (variable or uniform), the non-dimensional period number of the variable magnetic field (VMF) (0.2 ≤ Λ ≤ 0.8), the inclination angle of the VMF (0 ≤ χ ≤ 90), Rayleigh number (5 × 103 ≤ Ra ≥ 105) and Hartmann number (5 ≤ Ha ≥ 100) on thermal performance, heat transfer rate, entropy generation and flow patterns.Originality/valueTo the authors’ best knowledge, this paper is the first numerical investigation deals with the entropy generation and natural convection of hybrid nanofluid in a two-dimensional cavity, with specific thermal boundary conditions, containing an elliptical block under periodic-variable magnetic field. Different combinations between flow-governing parameters were made to find optimal thermal performance.

Study of Entropy Generation and Magnetohydrodynamic (MHD) Natural Convection in a Curved Enclosure Having Various Amplitude and Filled with Cu–TiO2/Water Hybrid Nanofluid

We have studied the buoyancy-driven convection enhancement and entropy production in a Cu–TiO2/water (water with copper and titanium dioxide nanoparticles) hybrid nanofluid filled curved enclosure subjected to a uniform magnetic field. The enclosure has a sinusoidally heated right wall, cold left wall, uniformly heated bottom wall, and thermally insulated upper curved wall. The effect of different amplitudes (concave, square, and convex) of the upper curved wall is considered. The non-linear governing equations are non-dimensionalized and written in stream function-velocity formulation. Bi Conjugate Gradient Stabilized (BiCGStab) method is employed followed by a Tri-diagonal matrix algorithm (TDMA) for the numerical simulation. The considered parameters are as follows: Rayleigh number (Ra), Hartmann number (Ha), phase angle (ε), the amplitude of the curved wall (a), and nanoparticle volume fraction (Φ). The influence of the model parameters on entropy production, fluid flow, and heat transfer phenomenon has been investigated, and the simulated results are displayed in terms of flow fields and temperature fields. According to the studies, increasing the Rayleigh number and volume percentage of nanoparticles has a significant impact on heat transmission and hence dominates the convection effect, whereas increasing the Hartmann number has the opposite effect.

Magnetohydrodynamics Natural Convection of a Triangular Cavity Involving Ag-MgO/Water Hybrid Nanofluid and Provided with Rotating Circular Barrier and a Quarter Circular Porous Medium at its Right-Angled Corner

Magnetohydrodynamics Natural Convection of a Triangular Cavity Involving Ag-MgO/Water Hybrid Nanofluid and Provided with Rotating Circular Barrier and a Quarter Circular Porous Medium at its Right-Angled Corner

Magnetohydrodynamic natural convection of a hybrid nanofluid from a sinusoidal wavy cylinder placed in a curve-shaped cavity

A numerical investigation has been executed in a curve-shaped enclosure crammed with a hybrid nanofluid containing a wavy-shaped inner cylinder with the existence of a magnetic field. A mixture of copper and alumina nanoparticles in a normal water-based solution is used to create the hybrid nanofluid. The natural convective flow in the enclosure is generated as a result of the temperature difference between a cold outer curve-shaped enclosure and a hot inner wavy cylinder. A numerical parametric examination is performed for several values of the Rayleigh number, volume concentration of nanoparticles, Hartmann number, and wave number of the inner cylinder. Outcomes are explained in terms of velocity field, isotherms, and local and average Nusselt numbers with changes in physically significant parameters. The outcomes reveal that the rate of thermal transmission is considerably augmented for rising the concentration of the hybrid nanofluid and Rayleigh number; however, with a higher Hartmann number, opposite tendency is exhibited. In addition, the intensity of the fluid flow and the heat transfer inside the enclosure are controlled by the number of waves in the internal cylinder.

Numerical simulation of thermal management during natural convection in a porous triangular cavity containing air and hot obstacles

A numerical study is presented of laminar viscous magnetohydrodynamic natural convection flow in a triangular-shaped porous enclosure filled with electrically conducting air and containing two hot obstacles. The mathematical model is formulated in terms of dimensional partial differential equations. The pressure gradient term is eliminated by using the vorticity–stream (\(\omega - \psi\)) function approach. The emerging dimensionless governing equations are employed by the regular finite difference scheme along with thermofluidic boundary conditions. The efficiency of the obtained computed results for isotherms and streamlines is validated via comparison with previously published work. The impact of physical parameters on streamlines and temperature contours for an extensive range of Rayleigh number (Ra = 103–105), Hartmann magnetohydrodynamic number (Ha = 5–30), Darcy parameter (Da = 0.0001–0.1) for fixed Prandtl number (Pr = 0.71) is considered. Numerical results are also presented for local and average Nusselt numbers along the hot base wall. Interesting features of the thermofluid behaviour are revealed. At lower Rayleigh number, the isotherms are generally parallel to the inclined wall and only distorted substantially near the obstacles at the left vertical adiabatic wall; however, with increasing Rayleigh number, this distortion is magnified in the core zone and simultaneously warmer zones expand towards the inclined cold wall. The simulations are relevant to magnetic materials processing and hybrid magnetic fuel cells.

Galerkin finite element analysis of thermal aspects of Fe3O4-MWCNT/water hybrid nanofluid filled in wavy enclosure with uniform magnetic field effect

In this contribution, a numerical investigation was made for heat transfer and steady magneto-hydrodynamic natural convection in a fined cold wavy-walled porous enclosure with a hot elliptic inner cylinder occupied by hybrid Fe3O4-MWCNT /water nanofluid. The enclosure is also placed in a uniform magnetic field. The governing equations are verified by using the Galerkin Finite Element Method (GFEM). Our numerical conclusions are expressed in terms of distributions of isotherms, Nusselt number, and streamlines, which are important, control parameters for the heat convection, and flow in the enclosure. The findings elucidate that the Nuavg rises with the growth of Ra, porosity ratio, and Da ratio increase, though it reduces with the growth of Hartmann number.

Unsteady MHD natural convection flow of a nanofluid inside an inclined square cavity containing a heated circular obstacle

Abstract The phenomena of unsteady magnetohydrodynamics (MHD) natural convection flow in an inclined square cavity filled with nanofluid and containing a heated circular obstacle at its center with heat generation/absorption impact are examined numerically. The cavity’s right and left walls are maintained at low temperatures, while the remaining walls are adiabatic. The volumetric external force, MHD, is applied across the inclined cavity. A penalty formulation-based finite element method is used to solve the nonlinear set of governing equations iteratively. The numerical scheme and results are validated through a comparison with the benchmark results, and it shows that our solutions are in good agreement with them. The results are shown in terms of contours of streamlines, isotherms, and average Nusselt number. It is observed that MHD alters the streamlines, isotherms, and average Nusselt number and dominates the flow as compared to any other physical parameter. The average Nusselt number is found sensitive to the central obstacle’s size, and it reduces sufficiently when the radius of the inner cylinder increases. For all the parameters, the streamlines’ symmetric pattern holds, such that the anti-clockwise cells on the left side of the cavity have their symmetric clockwise cells on the right side.

CNT–water nanofluid magneto-convective heat transfer in a cubical cavity equipped with perforated partition

This paper discusses the magneto-hydrodynamic natural convection in a cubical cavity equipped with a perforated separation. Several situations related to the number of perforations, magnitude of magnetic field, nanoparticles concentration and Rayleigh number are studied. During this study, the CNT–water filled cavity is differentially heated and a uniform external magnetic field is imposed. Computations are performed for Hartmann (0 ≤ Ha ≤ 100), (103 ≤ Ra ≤ 105 ), (3 × 3 ≤ N ≤ 7 × 7) and (0 ≤ ϕ ≤ 0.02). The results indicate that, the heat transfer is enhanced when the CNT volume fraction and Rayleigh number increase and decrease when the magnitude of the magnetic field increases. Moreover, the average Nusselt number has its highest values of the solid volume fraction and the number of perforations (ϕ = 0.02 and N = 7 × 7). Furthermore, it was seen that the number of perforations is more effective on heat transfer for higher Rayleigh number values.

MHD natural convection and entropy generation of non-Newtonian ferrofluid in a wavy enclosure

Two-dimensional laminar magneto-hydrodynamic (MHD) natural convection flow of non-Newtonian ferrofluid has been investigated to understand the characteristics of heat transfer, streamlines, isotherms, and entropy generation in a wavy enclosure using the finite volume method (FVM). The horizontal boundaries of the cavity are assumed to be thermally adiabatic, while the temperatures of the left and right vertical walls are presumed to be TH and TC, respectively. The rheology of the nanofluid is represented through the power-law model, and the density variations due to thermal expansion lie within the framework of the Boussinesq approximation. Numerical simulations have been carried out for a range of dimensionless parameters such as Rayleigh number (Ra=103,104,105), Hartmann number (Ha=0,10,20), power-law index (n=0.6,0.8,1.0,1.2,1.4), volume fraction (ϕ=0,0.05,0.1), and Prandtl number Pr = 6.8377. Results indicate that the isotherms of the shear-thinning fluid are dominated by thermal convection, whereas conduction is more pronounced for shear-thickening fluids. The average Nusselt number of the non-Newtonian ferrofluid increases with the attenuation of the Hartmann number and augmentation of the Rayleigh number, and in our entire simulation, the maximum value of Nu¯, due to the addition of ferro-particles, is found to be 8.07. The power-law index has a remarkable influence on the streamlines, and ψmax tends to decrease when n is increased gradually from shear-thinning to shear-thickening fluid behavior. Moreover, it is revealed that the heat transfer rate of ferrofluid (ϕ=10%) increases up to 26% for the shear-thinning case and 25% for the shear-thickening case, under the influence of the magnetic field. Further, it is inferred that the irreversibility due to heat transfer, fluid friction, and magnetic field for the shear-thinning, Newtonian and shear-thickening ferrofluids, can be minimized based on the optimal parametric combination. The increment of Hartmann number results in 60% attenuation of total entropy for shear-thinning fluid and 9% diminution for the shear-thickening case. With the augmentation of the power-law index, the entropy generation is found to decrease by 80% in the absence of the magnetic field effect and by 54% in the presence of it. A new correlation for the average Nusselt number is proposed for the shear-thinning fluids and shows a good agreement between the computed and predicted results.

Micropolar ferrofluid flow via natural convective about a radiative isoflux sphere

Current investigation scrutinizes the magnetohydrodynamic (MHD) natural convection flow of micropolar ferrofluid across an isoflux sphere with the impacts of thermal radiation and partial slip. Cobalt-nanoparticles with kerosene as the base fluid are considered. The governing partial differential conservation equations and convenient boundary conditions are rendered into a nondimensional form. The finite difference method (FDM) is then applied to determine the solution of a collection of resultant equations. The outcomes obtained by FDM have also compared with cited investigation. Illustrations describing influences of prominent parameters which provides physical interpretations of velocity, angular velocity, and temperature fields as well as the skin friction coefficient and Nusselt number are examined in detail with the help of graphical representations. This investigation determined that the skin-friction coefficient and heat transport rate reduced along with augmentation in the magnetic force and micropolar parameter, while opposite performance is adhered with elevating in the thermal radiation. Moreover, the boosted nanoparticle volume fraction reduced the skin friction coefficient and improved the Nusselt number.

Galerkin finite element analysis of magneto-hydrodynamic natural convection of Cu-water nanoliquid in a baffled U-shaped enclosure

In this paper, single-phase homogeneous nanofluid model is proposed to investigate the natural convection of magneto-hydrodynamic (MHD) flow of Newtonian Cu–H2O nanoliquid in a baffled U-shaped enclosure. The Brinkman model and Wasp model are considered to measure the effective dynamic viscosity and effective thermal conductivity of the nanoliquid correspondingly. Nanoliquid's effective properties such as specific heat, density and thermal expansion coefficient are modeled using mixture theory. The complicated PDS (partial differential system) is treated for numeric solutions via the Galerkin finite element method. The pertinent parameters Hartmann number (1 ≤ Ha ≤ 60), Rayleigh number (103 ≤ Ra ≤ 106) and nanoparticles volume fraction (0% ≤ ϕ ≤ 4%) are taken for the parametric analysis, and it is conducted via streamlines and isotherms. Excellent agreement between numerical results and open literature. It is ascertained that heat transfer rate enhances with Rayleigh number Ra and volume fraction ϕ, however it is diminished for larger Hartmann number Ha.

MHD‐free convection flow of CNTs differential type nanofluid over an infinite vertical plate with first‐order chemical reaction, porous medium, and suction/injection

In this research work, the magnetohydrodynamic natural convection carbon nanotubes (CNTs) flow of differential type nanofluid over an extended vertical surface in the presence of suction, heat generation, chemical reaction of the order first, through a porous medium has been analyzed. The governing equations of this physical model have been deduced by the law of conservation of mass, momentum, and energy. As a result temperature, velocity, and concentration fields have been obtained as the solutions of governing equations by utilizing Laplace transform technique. Some graphs of velocity profile have been plotted to see the effects of involved parameters like Prandtle number, Schmidt number, thermal and mass Grashof numbers, chemical reaction parameter, radiation parameter, magnetic field parameter, and volume fraction parameter of CNTs with suction/injection parameters on fluid motion.

Effect of heat generation and heat absorption on natural convection of Cu-water nanofluid in a wavy enclosure under magnetic field

Taking a more complex engineering geometry into account, magnetohydrodynamic natural convection of nanofluid (Cu-water) in a wavy walled enclosure having a circular hot cylinder inside is investigated by employing Galerkin-weighted residual formulation. In order to investigate the flow and heat transfer characteristics from several perspectives and increase the ability of adaptation to various engineering applications, the influences of the Hartmann number, Ha, Rayleigh number, Ra, and nanoparticle concentration are examined in detail. In addition to that, heat generation and heat absorption situations are also considered within the present work, which are simulated by a heat coefficient in a range of −10 ≤ q ≤ +10. The results revealed that increasing Ha has an insignificant effect on Nusselt number, Nu, at low Ra, however, it significantly pulls Nu down up to 33% for higher Ra, because of restricting convection. It is found that the heat coefficient, q, has a remarkable impact on Nu at low Ra, while its significance is diminished when Ra is increased. For q < 0, the heat absorption creates a heat sink, which increases Nu up to 34%, while the heat generation (q > 0) conversely reduces Nu up to 48%. Besides, variation in heat coefficient does not considerably affect the improvement impact of nanoparticles.

Numerical Simulation of MHD Natural Convection Flow Within Porous Trapezoidal Cavity With Heated Triangular Obstacle

A steady laminar two-dimensional finite element based Galerkin weighted residual numerical approach (GWRNA) has been adopted to solve magnetohydrodynamic (MHD) natural convective flow filled with porous medium in a trapezoidal cavity with various aspect ratio of heated triangular obstacle $$ (1/3 \le AR \le 1) $$ . The boundary location of the cavity consists of non-uniform heating of bottom wall whilst the two vertical walls are maintained at a cold temperature and the top wall is thermal insulated. For the simulation purpose, wide range of parameters, such as, Hartmann number (Ha = 50), Prandtl number (0.026 ≤ Pr ≤ 1000), Rayleigh number (103 ≤ Ra ≤ 106) and Darcy number (10−5 ≤ Da ≤ 10−1) are used in the cavity with various AR. The study demonstrated that the aforementioned parameters have strong influence on the stream functions and isotherms for different AR. A stronger flow circulation is observed for higher Ra and Da. Besides these, a symmetry for fluid flow simulations and isotherm contours are viewed. The result too unveils that the heat transfer rates as well as local and average Nusselt numbers strongly depend on various AR and abovementioned parameters.