Showing papers on "Hartmann number published in 2021"

Entropy generation on magneto-convective flow of copper–water nanofluid in a cavity with chamfers

Abstract: The irreversibility in convective nanofluid flow in the occurrence of a magnetic field (MHD) in a cavity with chamfers is calculated by numerical approach. The nanofluid flow is considered under the impacts of magnetic field and thermal gradient. The continuity, motion and energy equations are solved by applying COMSOL Multiphysics computer package. The impacts of $$({\text{Ha}})$$ Hartmann number, $$(\gamma )$$ elevation of magnetic field, nanoparticle volume fraction, heat transmission and entropy analysis on the flow of nanofluid are discussed. Results reveal that, the impacts of volume fraction and the magnetic force on different irreversibility are significant. Moreover, results indicate the existence of a critical $$({\text{Ha}}_{{\text{c}}} )$$ Hartmann number this represents the frontier between the domains where the magnetic field dominates via its intrinsic effect and its extrinsic effect.

A study of dual stratification on stagnation point Walters' B nanofluid flow via radiative Riga plate: a statistical approach

Abstract: Features of double stratification on stagnation point flow of Walter's B nanoliquid driven through Riga surface are examined in the current study. Via solutal stratification, radiation and thermal effects, heat and mass phenomena are evaluated. The novelty of the proposed investigation is focused on the important effect of melting phenomenon and EMHD Lorentz force along with stratification and heat generation over the rheology of the liquid flow. The influence of Brownian and thermophoresis particle deposition is included in transport equations involved in the analysis. Transformation is incorporated by the basic laws of mass, energy and linear momentum to acquire nonlinear differential system of equations. Utilizing Optimal Homotopy Analysis Method through BVPh2.0.0, optimum value of convergence control factors is estimated. Graphical findings for the dimensionless temperature, velocity and concentration for different pertinent parameters are explained. Numerical values of physical interest like skin friction coefficient, local Sherwood number and local Nusselt number are computed and visualized graphically. The heat generation and advanced modified Hartmann number improve the speed of flow. It is also observed that weaker thermal stratification upraises the rate of heat transport, and mass transport rate lessens for stronger mass stratification. In addition, contour graphs of velocity for ratio parameter A describe the accurate perception of flow. The intensity of temperature and concentration field is low owing to double stratification, whereas the stronger radiation corresponds the significantly rise in temperature. Reliability of outcomes assured by means of probable error analysis.

Magneto-hydrodynamic thermal convection of Cu–Al 2 O 3 /water hybrid nanofluid saturated with porous media subjected to half-sinusoidal nonuniform heating

Abstract: The present work aims to examine the thermal efficacy of half-sinusoidal nonuniform heating at different spatial frequencies for a porous natural convection system using Cu–Al2O3/water hybrid nanofluid and magnetic field. The system is presented utilizing a classical square enclosure heated nonuniformly at the bottom wall, and the sidewalls are allowed to exchange heat with the surroundings. The Brinkman–Forchheimer–Darcy model is adopted catering other additional terms for buoyant force and magnetic field. The governing equations are transformed into nondimensional forms and then solved numerically using a finite volume-based computing code. The importance and fundamental flow physics are explored in terms of the pertinent parameters such as the amplitude (I) and spatial frequency (f) of half-sinusoidal heating, Darcy–Rayleigh number (Ram), volume fraction of hybrid nanoparticles ( $$ \phi $$ ), and Hartmann number (Ha). The flow structure and heat transfer characteristics are analyzed and presented utilizing heatlines, streamlines and isotherms and average Nusselt number. The results show that the use of half-sinusoidal nonuniform heating along with hybrid nanofluid can be a viable method for enhancement and control of the overall thermal performance. The study indicates that half-sinusoidal heating could be a promising technique for better heat transfer even in the presence of flow dampening effects like porous media and magnetic fields.

Entropy generation and heat transport of Cu–water nanoliquid in porous lid-driven cavity through magnetic field

Abstract: Purpose The purpose of this paper is to investigate the effects of Ha and the Nanoparticles (NP) volume fraction over the irreversibility and heat transport in Darcy–Forchheimer nanofluid saturated lid-driven porous medium. Design/methodology/approach The present paper highlights entropy generation because of mixed convection for a lid-driven porous enclosure filled through a nanoliquid and submitted to a uniform magnetic field. The analysis is achieved using Darcy–Brinkman–Forchheimer technique. The set of partial differential equations governing the considered system was numerically solved using the finite element method. Findings The main observations are as follows. The results indicate that the movement of horizontal wall is an important factor for the entropy generation inside the porous cavity filled through Cu–water nanoliquid. The variation of the thermal entropy generation is linear through NPs volume fraction. The total entropy generation reduces when the Darcy, Hartmann and the nanoparticle volume fraction increase. The porous media and magnetic field effects reduce the total entropy generation. Practical implications Interest in studying thermal interactions by convective flow within a saturating porous medium has many fundamental considerations and has received extensive consideration in the literature because of its usefulness in a large variety of engineering applications, such as the energy storage and solar collectors, crystal growth, food processing, nuclear reactors and cooling of electronic devices, etc. Originality/value By examining the literature, the authors found that little attention has been paid to entropy generation encountered during convection of nanofluids. Hence, this work aims to numerically study entropy generation and heat transport in a lid-driven porous enclosure filled with a nanoliquid.

Impact of heated obstacle position on magneto-hybrid nanofluid flow in a lid-driven porous cavity with Cattaneo-Christov heat flux pattern

Abstract: This article mainly emphases on the study of magneto Cu-Al2O3/water hybrid nanofluid flow in a non-Darcy porous square cavity. The square geometry is a lid-driven enclosure with an inside heated square obstacle. Cattaneo-Christov heat flux pattern is used for the formulation of the heat equation. This type of problems may be applicable in the high temperatures in the different scientific processes, extrusion of polymers, aerodynamics extrusion and cooling hot glass. Dimensionless forms of governing flow expressions are computed numerically with Finite Volume Method via SIMPLER algorithm simultaneously. The characteristics of numerous dimensionless parameters such as; Richardson number 0.1 ⩽ R i ⩽ 100 , Hartmann number 0 ⩽ H a ⩽ 100 , height of hot square obstacle 0.1 ⩽ H ⩽ 0.5 , width of hot square obstacle 0.1 ⩽ W ⩽ 0.5 , Reynolds number 0.1 ⩽ R e ⩽ 25 and Darcy number 10 - 2 ⩽ D a ⩽ 10 - 6 are analyzed. The achieved results are projected graphically via streamlines, isotherms, local and average Nusselt numbers. The fluid flow and rate of heat transfer in the direction of the moving heated obstacle isfound to play an important role. The higher values of Ha decreases the local Nusselt number. Hybrid nanofluid provides a higher heat transfer rate than the nanofluids. Increasing the width of the obstacle cause to decline in the thickness of the right wall, this enhances the heat transfer in the clockwise direction.

Natural convection of CuO-water nanofluid in a conventional oil/water separator cavity: Application to combined-cycle power plants

Abstract: The oily water from various sources in combined cycle power plants is collected in oil/water separator in which the oil separates from water due to the density difference. The idea of the presented geometry is taken from conventional oil/water separators. This paper studies the natural convection of the CuO-water nanoliquid in a rectangular cavity with fins attached to the insulated wall and porous media. Discretion of Navier-Stokes equations is done by Finite Element Method and assumptions are laminar, steady and incompressible flow. Heat transfer performance and entropy generation are investigated for distinct Rayleigh numbers (103–105), Darcy numbers (10−2–10−4), and Hartmann numbers (0, 10, 20). Different sizes of the fins are also studied to show consequences of fin size on heat transfer in cavity. This is the first time that these parameters and their impacts on Nusselt number and entropy generation are studied for a conventional oil/water separator cavity. Corollaries demonstrate that increasing Rayleigh number and Darcy number improves heat transfer performance and average Nusselt number. Nevertheless, Hartmann number has a reverse effect with average Nusselt number. Finally, a new equation for average Nusselt number is developed with regard to Rayleigh number, Hartmann number, and Darcy number.

MHD mixed convection of localized heat source/sink in an Al2O3-Cu/water hybrid nanofluid in L-shaped cavity

Abstract: The effect of source/sink heat location and size on Magneto-hydrodynamic mixed convection in hybrid nanofluid of Al2O3-Cu/Water within the L-shaped cavity is studied in this paper Two uniform heat sources are put at the corners of the bottom walls of enclosure and the beginning and the end of L-shape enclosure set to be at the cold temperature The other parts of enclosure’s walls are supposed to be insulated The finite difference method and Boussinesq approximation is utilized to discrete the governing equations The fundamental flow physics and thermal behavior are explored in terms of pertinent parameters such as the effects of sink/source heat generation, magnetic field and angle, Hartmann number, cavity length ratio, and hybrid volume fraction on average and surface Nusselt number, streamlines, isotherms, and entropy generation are studied The results demonstrate that maximum amount of the sink power causes the best heat transfer performance

On the flow patterns and thermal control of radiative natural convective hybrid nanofluid flow inside a square enclosure having various shaped multiple heated obstacles

Abstract: This investigation reveals the flow patterns of natural convective hybrid nanofluid inside a square enclosure. The enclosure is presumed to be filled with water-based ferrous-graphene nanoparticles and multiple heated obstacles with various shapes. Three types of heated obstacles namely circular, square, and diamond are considered to visualize the flow patterns. The bottom and left-sided walls are presumed to be uniformly heated, whereas the top surface is adiabatic and the right-sided wall is made isothermally cooled. Moreover, thermal radiation and magnetic effects are supposed to exist within the flow region. A complete investigation is conducted to extract that how these different shaped heated obstacles influence the hydrothermal pattern. Appropriate similarity variables translate the dimensional equation into non-dimensional. Later on, Galerkin finite element scheme is introduced to deal with those nondimensional flow equations. The grid independence, comparison test, and experimental validation are conducted to exhibit the competency of the current model. Several isotherms, streamlines, velocity distribution, and average Nusselt number plots are depicted to perceive the parametric impact on such cavity flow. These plots are made for dimensionless factors such as Rayleigh number a $$\left( {10^{3} \le {\text{Ra}} \le 10^{5} } \right)$$ , thermal radiation $$\left( {0.5 \le N \le 1.5} \right)$$ , Hartmann number $$\left( {5 \le {\text{Ha}} \le 15} \right)$$ , nanoparticle volume fraction $$\left( {0.00 \le \phi_{2} \le 0.04} \right)$$ . The consequences imply that the isotherms intensify for Rayleigh number and extreme distortion is noted for circular obstacle, while other parameters disclose opposite scenario in isotherms. The average Nusselt number diminishes for Hartmann number but amplifies for nanoparticle concentration. The maximum increment in heat transport is predicted for Rayleigh number variation and circular obstacles. It is approximately 27.39%. The lowest enhancement is provided by diamond-shaped obstacles.

Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization

Abstract: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles.,The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite element method has been used.,The results show that Nuave is proportional to Rayleigh and nanoparticle shape factor directly as well as it has an inverse relation with Hartmann and porosity. The obtained results reveal that the shape factor parameter has a significant effect on the heat transfer performance, which shows a 55.44% contribution on the average Nusselt number.,As a novelty, to maximize the heat transfer performance in a corrugated walls enclosure, the optimal parameters have intended by using the response surface and Taguchi methods. Additionally, an accurate correlation for the average Nusselt number is developed with sensibly great precision.

Thermal-natural convection and entropy production behavior of hybrid nanoliquid flow under the effects of magnetic field through a porous wavy cavity embodies three circular cylinders

Abstract: In this numerical contribution, hybrid nanofluid flow behavior, thermal characteristics, and entropy generation analysis through a porous enclosure containing three circular cylinders with magnetic field effects were investigated using finite element approach. The cylinders are arranged in horizontal arrangement in the middle of cavity height, and the active hot central cylinder can move along the vertical central axis while other cold cylinders are considered fixed. The cylinders are enclosed by an adiabatic wavy cavity loaded with Cu-Al2O3-water. The results are discussed for the scrutinized parameters e.g., Rayleigh number (Ra), Darcy number (Da), Hartmann number (Ha), relative position of the hot cylinder (δ), and concentration in volume of nanoparticles (ϕ). It was inferred that the thermal-natural convective flow and overall heat transmission were reinforced by boosting Ra and Da, and lowering Ha. Changing the relative position of the hot cylinder has a remarkable effect on nanoliquid flow patterns, convective heat transfer and entropy generation characteristics.

Thermal analysis of Casson micropolar nanofluid flow over a permeable curved stretching surface under the stagnation region

Abstract: We consider a curved surface upon which the Casson micropolar nanofluid flow is discharged to understand the behavior of such flow and heat progression. The non-Newtonian fluid flow is controlled with the introduction of a magnetic force which is directed against the flow to alter the moment of flow. An increase in the numerical value of modified Hartmann number slows down the flow by adding discharge against the flow. Lorentz force produced by increasing the curve of the channel suppresses the flow velocity. The micropolar parameter reduces the drag and helps in increasing the fluid flow. Mathematical modeling of the problem is done by taking into account the conventional assumptions taken in fluid flow theories. The modeled equations are simplified by considering similar transformation variables used in the contemporary literature. Numerical result is obtained by using bvp4c solver used in MATLAB by allowing the acceptable tolerance level at 1e−4. Various tests are carried out to choose the best match of the parametric values which help in achieving the defined boundary conditions. The output of the various solutions is plotted under varying values of different parameters, and henceforth the changes occurred are noted and discussed. The behavior of velocity, microrotational, temperature and concentration profiles is observed by comparing the graphical and tabular values. The role of different physical quantities under different parametric assumptions for stretching/shrinking channel is also taken into account and highlighted.

Interaction of fusion temperature on the magnetic free convection of nano-encapsulated phase change materials within two rectangular fins-equipped porous enclosure

Abstract: The present study encountered the impact of non-dimensional fusion temperature on the free convection of conducting nanofluid within a porous enclosure filled with nano-encapsulated phase change materials (NEPCMs). The enclosure is equipped with two parallel fins that have ability to move in both directions such as vertically as well as horizontally. In particular the particles are structured as core-shell with phase change materials. The phase change of the materials is obtained from the solid to liquid and absorbs the surrounding temperature in the hot region and releases in the cold region. The governing transformed equations are tackled by using the Finite Element Method (FEM). The numerical simulation of the isotherms, streamlines and heat transfer coefficient ratio along with velocity distribution for various parameters are presented. These are affecting a key role on the average and local Nusselt number as well as on the local Bejan number. However, the measure outcomes are; both the longitudinal and transverse velocity profiles boost up with an augmented Rayleigh number; however, the weaker flow field is generated for the increasing Hartmann number.

Impact of stratification phenomena on a nonlinear radiative flow of sutterby nanofluid

Abstract: In the recent years, rapid developments in nanotechnology have developed a great prospects for researchers to check up. Thermal performance of nanofluid is well scrutinized by global scientists. Keeping aforesaid pragmatism of nanofluids, we have considered Sutterby liquid under thermophoretic and Brownian movement's aspects. Radiation and stratification phenomenon for thermal analysis of Sutterby nanoliquid are considered. By invoking some appropriate transformations and boundary conditions the given partial differential equations are converted into coupled system of ODEs (ordinary differential equations). Then by using Bvp4c algorithm, we resolved these ODEs numerically. Graphs are designed to check the behavior of appropriate parameters on velocity, temperature, and concentration distribution. Consequences extracts that increase in Hartmann number decays the velocity profile whereas opposite behavior is accounted for temperature distribution. It is also observed that for larger values of thermal stratification phenomenon deteriorates the transportation rate of heat. Furthermore, Sutterby fluid model calculates the features of pseudoplastic plus dilatant solutions. This study is very suitable for extraordinary polymer resolutions plus polymer melts.

Numerical Simulation of Hybrid Nanofluid Mixed Convection in a Lid-Driven Square Cavity with Magnetic Field Using High-Order Compact Scheme.

Abstract: In this study, the energy transference of a hybrid Al2O3-Cu-H2O nanosuspension within a lid-driven heated square chamber is simulated. The domain is affected by a horizontal magnetic field. The vertical sidewalls are insulated and the horizontal borders of the chamber are held at different fixed temperatures. A fourth-order accuracy compact method is applied to work out the vorticity-stream function view of incompressible Oberbeck-Boussinesq equations. The method used is validated against previous numerical and experimental works and good agreement is shown. The flow patterns, Nusselt numbers, and velocity profiles are studied for different Richardson numbers, Hartmann numbers, and the solid volume fraction of hybrid nanoparticles. Flow field and heat convection are highly affected by the magnetic field and volume fraction of each type of nanoparticles in a hybrid nanofluid. The results show an improvement of heat transfer using nanoparticles. To achieve a higher heat transmission rate by using the hybrid nanofluid, flow parameters like Richardson number and Hartmann number should be considered.

Heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid magnetic nanofluid flow in a trapezoidal wavy enclosure containing porous media with the Galerkin finite element method

Abstract: The present study addresses theoretically and computationally the performance of electrically conducting water-Fe3O4/CNT hybrid nanofluid in three-dimensional free convection and entropy generation in a wavy-walled trapezoidal enclosure. The enclosure has two layers—a hybrid nanoliquid layer and a permeable medium layer. A transverse magnetic field is acting in the upward direction. Newtonian flow is considered, and the modified Navier–Stokes equations are employed with Lorentz hydromagnetic body force, Darcian and Forchheimer drag force terms. The wavy side walls are heated while the top and vertical walls are adiabatic. An elliptic cylindrical cooled fin is positioned at the center of the cavity, and several different tilting angles of the fin are considered. The transformed, non-dimensional systems of coupled nonlinear partial differential equations with their corresponding boundary conditions are solved numerically with the Galerkin Finite Element Method (FEM) using the COMSOL Multiphysics software platform. The impact of Darcy number, Hartmann number, volume fraction, undulation number of the wavy wall and Rayleigh number (thermal buoyancy parameter) on the streamlines, isotherms and Bejan number contours are investigated. Extensive visualization of the thermal flow characteristics is included. With increasing Hartmann and Rayleigh numbers, the average Bejan number is reduced strongly whereas the average Nusselt number is only depleted significantly at very high values of Rayleigh and high Hartmann numbers. With increasing undulation number, a slight elevation in average Bejan number at intermediate Rayleigh numbers is noticed, whereas the average Nusselt number is substantially boosted, and the effect is maximized at a very high Rayleigh number where the average Nusselt number was increased by 35%. An increment in Darcy number (i.e., reduction in permeability of the porous medium layer) is observed to considerably elevate the average Nusselt number at high values of the Rayleigh number up to 20%, whereas the contrary response is computed in average Bejan number, where it showed a reduction by 10 times. The simulations apply to hybrid magnetic nanofluid fuel cells and electromagnetic nanomaterials processing in cavities.

MHD mixed convection of Ag–MgO/water nanofluid in a triangular shape partitioned lid-driven square cavity involving a porous compound

Abstract: In the current study, magnetohydrodynamics mixed convective flow of Ag–MgO/water hybrid nanofluid in a triangular shaped partitioned cavity involving a porous layer is numerically investigated by using the finite element method. In the numerical simulation, various effects of pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 60), magnetic field inclination angle (between 0 and 90), Darcy number (between $$10^{-4}$$ and $$5 \times 10^{-2}$$ ), location of the vertex of triangular porous region (between 0.2 and 0.8 H) and hybrid nanoparticle solid volume fraction ( $$\phi _1$$ between 0 and 0.01, $$\phi _2$$ between 0 and 0.01) on the fluid flow and convective heat transfer features are examined. It was observed that a large vortex is established below the main vortex near the upper wall for the lowest value Ri number. At the highest magnetic field strength, multi-recirculation flow pattern is seen in the right bottom corner. The average heat transfer enhances with higher values of permeability of the porous medium, magnetic field inclination angle, distance of the porous layer vertex from the hot wall and solid nanoparticle volume fraction of each particles in the hybrid nanofluid. The impact is reverse for higher values of Richardson number and Hartmann number. In the current work, significant changes in the average Nusselt number are obtained by varying the location of the porous medium. The triangular shaped porous compound can be used as an excellent tool for convective heat transfer control.

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

Abstract: The current paper studied the behavior of a triangular cavity occupied with Ag-MgO/water nanofluid under MHD natural convection and provided with a rotating circular barrier, while the right-angled corner is equipped with quarter-circle porous medium and maintained at a fixed hot temperature Th. Several parameters are tested such as Rayleigh number (103 ≤ Ra ≤ 106), Hartmann number (0 ≤ Ha ≤ 80) and Darcy number (10−5 ≤ Da ≤ 0.15). The obtained results depict the enhancing effect of Ra and the controlling role of the magnetic parameter on heat transport. Increasing the characteristics of the porous media such as the porosity and the permeability showed a substantial impact on the heat transport efficiency within the enclosure. Moreover, the novelty findings in this paper are principally illustrated in the boosting impact of raising the porous medium thickness when it is associated with the growing up of the heated parts of the geometry by increasing the dimension of the radius (rp). Also, the rotational velocity (ω) and the radius (rob) of the circular obstacle are tested and showed an important influence on the energy transport within the cavity. Moreover, the obtained results by modifying the length (a) prove its pertinent influence on the heat transfer performance.