Magnetic Field Inclination Research Articles

Optimization of bifurcating channel cooling system for double inclined conductive panel system under inclined magnetic field

A novel cooling system with wavy branching channels is proposed considering nano-enhanced magnetic field effects for thermal management of double inclined conductive panels. Thermal performance assessment is conducted by varying Reynolds number (250≤Re≤1000), Hartmann number (0≤Ha≤400), magnetic field inclination (250≤γ≤1000), amplitude (0≤Af≤0.4) and wave number (1≤Nf≤12). As the cooling fluid, water with Ag–MgO hybrid nanoparticles is considered. Temperature drops of 4.5 °C and 2.6 °C are obtained with the highest Re for left inclined panel (p1) and right inclined panel (p2). As the vortex distribution is highly affected for the wavy branching channels by the magnetic field strength, its impact on the cooling performance for p1 and p2 are different. It shows a favorable impact for panel p2 while average Nusselt number (Nu) increments become 10% and 6.3% when using flat and wavy branching channels at the highest magnetic field strength. For panel p1, varying inclination of magnetic field results in average surface temperature drop of 1.6 °C for wavy channel. The optimum value of wave number in the corrugated branching channel is Nf=2 for achieving the highest cooling performance while higher amplitudes of corrugation has favorable impacts on the cooling for each of the panels. As compared to un-cooled panel configuration, utilization of flat branching channel with nano-enhanced magnetic field results in 47.4 °C and 48.9 °C surface temperature drops for panels p1 and p2. Optimization based on COBYLA is utilized to achieve additional temperature drops as compared to parametric computational fluid dynamics. The optimum values of (Ha, γ, Af) are obtained as (40, 89, 0.04) at Re=100 and (40, 60.8, 0.0038) at Re=1000. The proposed single cooling method with wavy branching channel under nano-enhanced magnetic field can be used and further developed for effectively cooling of photo-voltaics with inclined arrangement, electronic cooling and many other heat transfer devices.

Magnetohydrodynamic double-diffusive mixed convection in a curvilinear cavity filled with nanofluid and containing conducting fins

This work numerically analyzes the mixed convective double diffusion of Fe3O4-water-based nanofluid in a tilt curvilinear lid-driven cavity studied under the effect of an inclined magnetic field. The horizontal upper wall is at a lower thermal and concentration gradient and moves toward the right. The side vertical walls and bottom walls kept adiabatic. Furthermore, two numbers of conducting fins are affixed to the inclined walls at high temperatures and concentrations. The finite element approach is implemented to analyze the considered variables: Richardson number (Ri), Hartmann number (Ha), Reynolds number (Re), Lewis number (Le), buoyancy ratio (N), magnetic inclination angle (α), nanofluid volume fraction (ϕ) as well as the fins length on the heat and mass transport phenomena. The results showed that the Nuavg and Shavg increase by increasing Reynolds number, the nanoparticles volume concentration, and the fin length, while they decrease by increasing Hartmann number. When Ri is small, Nuavg rises with the increasing magnetic field inclination, but when Ri is high, the inclination angle works adversely. On the other hand, the Shavg increases with the rise of the magnetic field inclination for all Ri values. It can be seen also, when Lewis number increases, the Nuavg and Shavg values increase with increasing Ri and magnetic inclination angles.

Hydromagnetic flow of two immiscible nanofluids under the combined effects of Ohmic and viscous dissipation between two parallel moving plates

The hydromagnetic flow of immiscible nanofluids between two parallel plates is investigated. Two regions, namely, (i) Region 1 is filled with base fluid kerosene oil with silver Ag nanoparticles, while (ii) Region 2 is filled with base fluid water with titanium dioxide TiO2 nanoparticles. Analytic solutions of nonlinear coupled differential equations have been obtained. The velocity and temperature profile results are discovered to flatten out when the magnetic field's inclination angle decreases. Impact of key parameters like inclination of the magnetic field, Hartmann number and load parameter with thermal conductivity ration have been illustrated graphically.

MHD FLOW PAST OVER OSCILLATING VERTICAL PLATE THROUGH POROUS MEDIA IN THE PRESENCE OF HALL EFFECT AND CHEMICAL REACTION

MHD flow past over oscillating vertical plate with variable temperature and mass diffusion through a porous medium in the presence of Hall current effect and chemical reaction is studied here. The MHD fluid model contains partial differential equations of momentum, energy and diffusion equations. The Laplace-transform technique used to find the exact solution of equations involved in this paper. The resultant velocity profile is discussed with the help of graphs drawn for different parameters like, inclination of magnetic field, chemical reaction parameter, phase angle parameter and permeability parameter, and the numerical values Sherwood number have been also tabulated. It is noticed that the values obtained for velocity, concentration and temperature profiles are in concurrence with the actual flow of the unsteady MHD fluid.

Effect of the Curvature Angle in a Conduit with an Adiabatic Cylinder over a Backward Facing Step on the Magnetohydrodynamic Behaviour in the Presence of a Nanofluid

A backward facing duct are present in various industrial applications especially those focused on heat transfer. The flow through a curved backward facing duct especially in the presence of nanofluid presents complexities compared to a straight backward facing step (BFS) duct. Therefore, the present numerical study deals a nanofluid flow (Fe3O4-H2O) forced convection in a curved backward facing duct. The objective of this investigation is to visualize at different curvature angles g (0°, 30°, 45°, 60°, 90°) imposed on the top wall of the duct, the effect of Hartmann number Ha (0, 50, 100), magnetic field inclination angle γ (0°, 60°, 90°), Reynolds number Re (10, 100, 200) and nanoparticle volume fraction φ (0 %, 0.05 %, 0.1 %). The dimensionless governing equations are solved using the multigrid finite element method. The results showed that the heat transfer was enhanced at the curved angle g = 90° for large Hartman numbers, thus, the average Nusselt number increased with a ratio of 240.74 % in the case of Hartmann number (Ha = 100).

Thermal performance assessment by using a wavy porous obstacle in a circular vented cavity under non-uniform magnetic field during forced convection of hybrid nanofluids

In this study, effects of using a wavy porous object on the thermal performance improvement in circular vented cavity are numerically assessed during hybrid nanofluid convection under non-uniform magnetic field. Numerical analysis is conducted for varying values of Reynolds number (Re, between 200 and 1000), Hartmann number (Ha between 0 and 50), magnetic field inclination (γ between 0 and 90) while Darcy number is taken between and . The amplitude is considered between 0 and 0.5 while wave number of the corrugated porous object is taken between 2 and 16. Significant impacts of the porous object parameters and permeability on the flow pattern distribution and thermal performance improvements are obtained. The magnetic field improves the heat transfer for the lower permeability object case at Ha = 10 while the average Nusselt number (Nu) is reduced for the case with higher permeability object case. Average Nu number improvement up to 33.5 is obtained with the imposed non-uniform magnetic field effects. Average Nu variations of 27.3 and 15 are obtained when the corrugation wave number and amplitude are varied. The Constrained Optimization BY Linear Approximations optimization is used to achieve the highest thermal performance of the configurations.

Coronal Magnetic Fields Derived with Images Acquired during the 2017 August 21 Total Solar Eclipse

The coronal magnetic field, despite its overwhelming importance to the physics and dynamics of the corona, has only rarely been measured. Here, electron density maps derived from images acquired during the total solar eclipse of 2017 August 21 are employed to demonstrate a new technique to measure coronal magnetic fields. The strength of the coronal magnetic fields is derived with a semiempirical formula relating the plasma magnetic energy density to the gravitational potential energy. The resulting values are compared with those provided by more advanced coronal field reconstruction methods based on MHD simulations of the whole corona starting from photospheric field measurements, finding very good agreement. Other parameters such as the plasma β and Alfvén velocity are also derived and compared with those of MHD simulations. Moreover, the plane-of-sky (POS) orientation of the coronal magnetic fields is derived from the observed inclination of the coronal features in filtered images, also finding close agreement with magnetic field reconstructions. Hence, this work demonstrates for the first time that the 2D distribution of coronal electron densities measured during total solar eclipses is sufficient to provide coronal magnetic field strengths and inclinations projected on the POS. These are among the main missing pieces of information that have limited so far our understanding of physical phenomena going on in the solar corona.

Magnetic Inclination Evolution of Accreting Neutron Stars in Intermediate/Low-mass X-Ray Binaries

The magnetic inclination angle χ, namely the angle between the spin and magnetic axes of a neutron star, plays a vital role in its observational characteristics. However, there are few systematic investigations of its long-term evolution, especially for accreting NSs in binary systems. Applying the model of Biryukov & Abolmasov and the binary evolution code MESA, we simultaneously simulate the evolution of the accretion rate, spin period, magnetic field, and magnetic inclination angle of accreting NSs in intermediate/low X-ray binaries. We show that the evolution of χ depends not only on the initial parameters of the binary systems, but also on the mass transfer history and the efficiency of pulsar loss. Based on the calculated results we present the characteristic distribution of χ for various types of systems including ultracompact X-ray binaries, binary millisecond pulsars, and ultraluminous X-ray sources, and discuss their possible observational implications.

Nano-jet impingement cooling of a sinusoidal wavy hot surface by using an oriented L-shaped object under magnetic field with two phase mixture formulation

In this study, slot nano-jet impingement cooling of a wavy sinusoidal surface is analyzed by combined utilization of an oriented L-shaped object and magnetic field. A two phase mixture model of nanofluid is adopted. It is observed that the presence of the L-shaped object and its orientation are very influential on the local and average heat transfer performance. Magnetic field suppresses the vortices near the object and on the bottom all. The average Nusselt number (Nu) rises by 17.5% and 8.6% when its strength is varied for object orientations of te=−90 and te=90. When magnetic field inclination is concerned, the cooling performance improvements are in the range of 25.6%–53.9% depending upon the orientation of the object. The orientation of te=0 and te=45 are the most favorable cases in terms of thermal performance while significant variations in the average Nu are seen in the absence of magnetic field when varying the L-shaped object orientation. When compared to reference case of slot jet impingement (without magnetic field using pure fluid and without object), using nanofluid improves the cooling performance by about 8.4%. When object is installed at Ha=0, it rises by 27% at orientation of te=45. When magnetic field is used, additional rise of thermal performance with nanofluid is obtained up to 10% when compared to case by using only pure fluid.

CuO–Water MHD Mixed Convection Analysis and Entropy Generation Minimization in Double-Lid–Driven U-Shaped Enclosure with Discrete Heating

Abstract The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heating using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°– 90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°– 90°). It was found that the N um and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained by increasing Ha and α. The optimum magnetic field and cavity inclination angles to maximum heat transfer are γ = 90° and α = 0.

Numerical investigation of magneto-thermal-convection impact on phase change phenomenon of Nano-PCM within a hexagonal shaped thermal energy storage

Latent heat storage is among the most effective thermal energy storage techniques. The heat can be stored or released in a phase change substance undergoing melting or solidification. The present research addresses the melting process of paraffin, a phase change material, enhanced with metallic alumina nanoparticles, inside a hexagonal heat storage unit in the presence of a uniform magnetic field is investigated. The melting process occurs during the thermal charge of the latent heat storage unit. The enthalpy-porosity method was employed to model the melting process. The influence of the Lorentz force strength and magnetic field inclination angle as well as the nanoparticle concentration on charging level was scrutinized. It was found that the Lorentz force can suppress the charging level of the thermal energy storage system, while the magnetic field inclination angle can be suitable to control the energy transport performance and melting motion within the thermal energy storage unit. Moreover, raising the nanoadditives concentration diminishes the melting process. Overall, the obtained results confirmed that altering the intensity or direction of the external magnetic field presents indeed a mean for controlling the flow and thermal behavior of nano-enhanced phase change materials. Imposing the Ha up to 500 increases 266% the dimensionless melting time compared to ignoring magnetic field (Ha = 0).

Measured viscosity characteristics of Fe3O4 ferrofluid in magnetic and thermal fields

The rheological mechanisms governing the viscosity characteristics of nano-ferrofluids are very complicated; there is no universal theoretical treatment that explains the dependence of the ferrofluid viscosity on the flow, magnetic, and temperature fields. Thus, determining the viscosity characteristics of ferrofluids in various physical fields is of great theoretical and practical significance. This study explores experimentally the relationship between the ferrofluid viscosity and temperature, magnetic-field strength, and magnetic-field inclination. A special experimental bench on which the magnetic field and temperature can be precisely controlled is designed and constructed. It is found that the ferrofluid viscosity is negatively correlated with temperature. Increasing the percentage of the magnetic particles in the ferrofluid increases the viscosity at any given temperature. Ferrofluids are shown to exhibit the magnetic–viscosity phenomenon: under the action of a magnetic field, the viscosity increases until a magnetic viscosity saturation value is reached. Increasing the magnetic field inclination can aggravate the magnetic–viscosity phenomenon but does not change the saturation value. Contrary to the naïve Hall theory but in agreement with earlier phenomenological studies, the magneto-viscous effect is greater with horizontal than with vertical magnetic fields. Simultaneous exposure to temperature and magnetic fields is investigated; the two fields appear to act independently on the viscosity. The magnetic viscosity saturation value is not affected by temperatures in the range of 30–60 °C.

Convection analysis of the radiative nanofluid flow through porous media over a stretching surface with inclined magnetic field

Nanofluids flow through porous media constitutes an emerging perspective in many thermodynamic processes and thermal processing optimization. The primary goal of contemporary research from the standpoint of such thermal applications is to examine the nanofluid flow across a vertically placed stretching surface embedded in a porous media. The mathematical formulation of the considered flow is modeled with the consequences of inclined magnetic field and thermal radiations. The Darcy-Forchheimer-Brinkman model addresses the fluid transport within the porous medium. Carbon nanotubes (CNTs) and alumina ceramics are considered nanoparticles and porous media, respectively, and water is regarded as a base fluid in this study. Appropriate transformations have been developed to reduce the governing equations into the dimensionless system. The highly nonlinear transformed system is addressed by using a local non-similarity approach via the bvp4c built-in MATLAB function. The physical implications of the emerging dimensionless parameters on the velocity and thermal profiles of considered nanofluids are studied and discussed in detail. It is perceived that the thermal profile of nanofluid is enhanced with increasing estimations of nanoparticles concentrations and radiation parameters. Furthermore, an increment in Hartmann's number and magnetic field inclination angle diminishes fluid velocity. Furthermore, increasing the Darcy number reduces the temperature distributions of the nanofluids under consideration. Comparing the current study with published articles is also performed to corroborate the reported results. In this regard, an excellent agreement has been achieved. This work is expected to provide important information for the future implementation of innovative heat transfer devices, as well as a valuable reference for researchers studying nanofluids flows under varied assumptions.

Study of two-electron temperature plasma sheath using non-extensive electron distribution in presence of an external magnetic field

In this study, the physics of sheath formation in a collisional two-electron temperature plasma in the presence of an oblique external magnetic field has been investigated. At first, a comparative study among the fluid electron model, Boltzmann electron model, and the non-extensive electron model has been carried out and a suitable range of non-extensive parameter q has been predicted. In the latter part, a collisional two-electron temperature plasma is considered. Both the hot and cold electron densities are described using the non-extensive distribution, whereas cold ions are described by the fluid equations. The properties of the sheath are investigated in different collisional regimes by varying the non-extensive parameter (q) and the hot to cold electron densities and temperatures. The magnetic field inclination angle is varied in the limit 1° ≤ α ≤ 5°. It is observed that electron distribution significantly deviates from Boltzmann distribution for nearly parallel magnetic field. Moreover, collision enhanced flux deposition for highly magnetized case is a significant finding of the study. The results obtained in this study can enhance the understanding of plasma–matter interaction processes where multiple electron groups with near parallel magnetic field are found.

ITER relevant multi-emissive sheaths at normal magnetic field inclination

Reliable modeling of macroscopic melt motion induced by fast transients requires the accurate and computationally efficient description of the emitted current density that escapes to the pre-sheath. The ITER sheaths that surround hot tungsten surfaces during edge-localized modes are characterized by important contributions from secondary electron emission and electron backscattering as well as by the coupling between thermionic emission and field electron emission. Under the guidance of systematic particle-in-cell simulations that incorporate a comprehensive analytical electron emission model, a highly accurate semi-empirical treatment of the escaping electron current has been achieved.

Towards the impact of GMC collisions on the star formation rate

ABSTRACT Collisions between giant molecular clouds (GMCs) are one of the pathways for massive star formation due to the high densities created. However, the enhancement of the star formation rate (SFR) is not well constrained. In this study, we perform a parameter study of cloud–cloud collisions and investigate how the resulting SFR depends on the details of set-up. Our parameter study explores variations in collision speed, magnetic field inclination (with respect to the collisional axis), and resolution, as defined by the number of cells per Jeans length. In all our collision simulations, we find a factor of 2–3 increase in the SFR compared to our no collision simulation, with star formation beginning sooner with (a) high collisional velocities, (b) parallel orientation between the magnetic field and collision axis, (c) and lower resolution. The mean virial parameter of high density (and thus possible star-forming) gas increases with collisional velocity, but has little variation with magnetic field inclination. The alignment of the velocity and magnetic field remains uniform in low-density environments but becomes more perpendicular with increasing density, indicating the compression of the magnetic field by collapsing gas. Comparing the trends in the SFR with other GMC collision studies, we find good agreement with studies that account for the gravitational boundedness of the gas in their star formation algorithm, but not with those that simply form stars above a prescribed density threshold. This suggests that the latter approach should be used with caution when modelling star formation on resolved cloud scales.

Second Law Analysis of MHD Forced Convective Nanoliquid Flow Through a Two-Dimensional Channel

Abstract The present study deals with fluid flow, heat transfer and entropy generation in a two-dimensional channel filled with Cu–water nanoliquid and containing a hot block. The nanoliquid flow is driven along the channel by a constant velocity and a cold temperature at the inlet, and the partially heated horizontal walls. The aim of this work is to study the influence of the most important parameters such as nanoparticle volume fraction (0%≤ϕ≤4%), nanoparticle diameter (5 nm≤dp≤55 nm), Reynolds number (50≤Re≤200), Hartmann number (0≤Ha≤90), magnetic field inclination angle (0≤γ≤π) and Brownian motion on the hydrodynamic and thermal characteristics and entropy generation. We used the lattice Boltzmann method (LBM: SRT-BGK model) to solve the continuity, momentum and energy equations. The obtained results show that the maximum value of the average Nusselt number is found for case (3) when the hot block is placed between the two hot walls. The minimum value is calculated for case (2) when the hot block is placed between the two insulated walls. The increase in Reynolds and Hartmann numbers enhances the heat transfer and the total entropy generation. In addition, the nanoparticle diameter increase reduces the heat transfer and the irreversibility, the impact of the magnetic field inclination angle on the heat transfer and the total entropy generation is investigated, and the Brownian motion enhances the heat transfer and the total entropy generation.

Combined effects of using multiple porous cylinders and inclined magnetic field on the performance of hybrid nanoliquid forced convection

Effects of combined utilization of inclined magnetic field and multiple porous cylinders on the forced convection in a vented cavity are numerically assessed by using finite element method. Effects of Reynolds number (Re: 200–1000), magnetic field strength (Ha: 0–75), inclination of magnetic field (γ: 0–90), permeability of the porous cylinders (Da: 10−4−10−1) and size of the cylinders (R: 0.04 H–0.15 H) on the fluid flow convective heat transfer performance are studied. The presence of the cylinder and their permeability can be used for controlling the heat transfer. When cylinders at the highest permeability is used, there is 77% additional contribution to the overall thermal performance when lowest and highest Re cases are compared. There is significant contribution of the magnetic field on the suppression of the vortices in the cavity for the case with lower permeability of the cylinders. The magnetic field strength is more effective on the flow field and heat transfer as compared to its inclination. Up to 123% increment in the heat transfer is obtained at the highest strength of magnetic field for the highest permeability of the cylinders while it is only 12% when cylinders with the lowest permeability are used. When variation in the magnetic field inclination is considered, average heat transfer variation up to 19.8% is obtained for the multiple cylinders with the highest permeability. The size of the porous cylinders generally contributes positively to the overall thermal performance. Heat transfer enhancements up to 88% can be obtained by using highest cylinder size as compared to lowest size when the permeability is lowest while it is only 15% for the highest permeability case. The optimum set of parameters at Re = 200 is found as Ha, γ, Da) = (74.4, 1.3, 10−5) and at Re = 1000, it is (Ha, γ, Da) = (75, 0.35, 10−5). Significant variations in the average heat transfer is obtained when optimum case is compared with the parametric study case.

Gaseous slip flow in a porous two-dimensional rectangular microchannel subjected to inclined magnetic field

In this study, two-dimensional, steady, laminar, and compressible gaseous flow of Newtonian fluid in a rectangular porous microchannel affected by an electromagnetic field, and under local thermal equilibrium condition was analytically investigated in the slip flow region (0.001<Kn < 0.1). The porous microchannel is entirely affected by uniform inclined magnetic field with an angle α from the positive x-axis, the range of this angle is 0 ≤ α ≤ 90°. Also, the porous microchannel effected by uniform electric field which points in the positive z-direction. Thermophysical properties of the fluid were assumed to be constant. The normalized governing equations were asymptotically solved and expressions of the flow velocity components, the pressure, and the temperature were provided using first-order velocity slip and temperature jump boundary conditions. The effects of various parameters on the flow were studied, such as Darcy number, the porosity, the thermal conductivity ratio, the electrical conductivity ratio, Hartmann number, Knudsen number, the electric field to magnetic field ratio (0 ≤ K ≤ 1), and the magnetic field inclination angle. It was found that increasing the permeability of the porous medium increases the flow velocity but decreases its temperature. Further, the results reveal that applying a stronger magnetic field in absence of electric field decreases the flow velocity but increases its temperature. On the other hand, the stronger the electric field, the higher the flow velocity and its temperature. Also, as the magnetic field inclination angle increases the flow velocity decreases. The effects of Darcy number and the electrical conductivity ratio on the heat flux were studied as well. A comparison of the analytical solutions with the numerical results were presented as a validation for this study. The comparison showed that the analytical results were in good agreement with the numerical results.

Effect of discrete heating-cooling on magneto-thermal-hybrid nanofluidic convection in cylindrical system

In search of efficient energy utilization and superior thermal performance, the present study is aimed at understanding the positional effect of discrete heaters and coolers on a cylindrical thermal system. This system undergoes a magneto-thermal convective process using Cu-Al2O3H2O hybrid nanofluid. Four options are investigated by altering the position of four heater and cooler segments mounted centrally on the wall of four quadrants of the cylinder. The equations of motion and energy are solved in nondimensionalized form by employing the finite element technique. The effects of operating parameters on the thermal transport are investigated systematically for a fixed nanoparticle volume fraction (φ) and a range of the Rayleigh number (signifying the buoyant forces), Hartmann number (signifying the magnetic field strength), and the magnetic field inclination (γ). The study shows that heat transfer, as well as entropy production, is markedly influenced by the heater-cooler positions and flow-controlling parameters. Among all the studied configurations, two cases show the optimum value of the Nusselt number. The cross heater-cooler arrangement affirms as the most effective heating-cooling option to obtain enhanced heat transfer. Higher heat transfer corresponds to greater entropy production. Higher magnetic field intensity dampens the heat transfer rate and thermodynamic irreversibility. The innovative identification of superior cross-wise heating-cooling over the usual side-side or bottom-top heating-cooling is the major outcome of this study. The experimental hybrid nanofluid properties are considered for this study.