Mixed Convection Of Nanofluid Research Articles

Unsteady homogeneous-heterogeneous reactions in MHD nanofluid mixed convection flow past a stagnation point of an impulsively rotating sphere

This paper establishes a mathematical analysis for describing the homogeneous and heterogeneous chemical reactions in the nearness of stagnation region of a sphere immersed in a single-phase nanofluid due to a Newtonian heating. The flow is resulted by an impulsively rotating sphere, and the nanofluid involves nanoparticles of Copper and Ferro. The available unsteady-states of the considered system are given in the case when the diffusion coefficients of both reactant and auto catalyst have the same size. The resulting non-linear dimensionless coupled partial differential equations in which governing the mixed convection flow have been tackled numerically via an implicit finite difference technique in combination with the quasi-linearization scheme. The similarities and differences in the behavior of physical pertinent fluid parameters have been elaborated and discussed graphically. It has been clarified that the nanofluid velocity and temperature profiles grow gradually by adding nanoparticles in the base fluid. Again it is noticed from present contribution that concentration of the nanofluid is decreases function by rising the strength of homogeneous and heterogeneous chemical reactions. Finally, numerical computations of the skin friction and heat transfer factors are presented.

Mixed convective nanofluid flow over a non linearly stretched Riga plate

The present article concentrates on the heat and mass transfer characteristics of a mixed convective flow of an electrically conducting nanofluid past a slender Riga plate in the presence of viscous dissipation and chemical reaction. The heat and mass transfer characteristics are analyzed by a zero nanoparticle mass flux and convective boundary conditions. The thermophoretic and Brownian aspects for nanoliquid are proposed using Buongiorno's relations. The similarity quantities are utilized to obtain dimensionless forms of flow field equations. The resulting coupled nonlinear equations associated with the constituted boundary assumptions analytically proceed via optimal homotopy analysis method (OHAM). Various parameters causing the change in distributions of velocity, temperature, and concentration are graphically explained with relevant physical references. One of the important observations of the present study is, for higher values of modified Hartmann number the velocity profile increases and temperature profile supreses and it is interesting to note that the contemporary numerical simulations offer confirmable accuracy in the existing literature, which authenticates the novelty of current investigation.

A New Thermal Conductivity Model and Two-Phase Mixed Convection of CuO-Water Nanofluids in a Novel I-Shaped Porous Cavity Heated by Oriented Triangular Hot Block.

This paper investigates the cooling performance of nanofluid (NF) mixed convection in a porous I-shaped electronic chip with an internal triangular hot block using Buongiorno’s two-phase model. This type of cavity and hot block geometry has not been studied formerly. The NF was assumed to be a mixture of water and CuO nanoparticles (NP) up to 4% of volume concentration. As most published mathematical models for the thermal conductivity of NF give inaccurate predictions, a new predictive correlation for effective thermal conductivity was also developed with a high accuracy compared to the experimental data. The results showed that any increase in the NP volume concentration enhances the average Nusselt number () and the normalized entropy generation, and reduces the thermal performance of the cavity in all orientations of the hot block. The maximum enhancement in cooling performance was 17.75% and occurred in the right-oriented hot block in the sand-based porous cavity. Furthermore, adding the NP to the base fluid leads to a more capable cooling system and enhances the irreversibility of the process.

Impact of heat source on combined convection flow inside wavy-walled cavity filled with nanofluids via heatline concept

The appearance of a heat source at the bottom of a cavity against the cold part at the top wavy surface is examined in this work. The heat transportation, velocity of the fluid, and the temperature behaviour toward the mixed convection of nanofluids are obtained from the simulation of the Galerkin finite element technique and the Navier-Stokes equations. The other surfaces are considered adiabatic as well as both sides of the lid-driven cavity. It should be noted that the Grashof number, the volume fraction of alumina-nanoparticles, and the differentially-moving vertical walls are fixed at 105,0.02, the upward (right) and downward (left), respectively. To verify the computational code of derivation, the experimental and theoretical data from other researchers are compared. The results of the non-primitive variables, including the Richardson number, Reynolds number, number of undulations, dimensionless length, and the location of the heat source are compared. The numerical results indicate that larger values of the Richardson number and the Reynolds number enhance the rate of heat transfer. Not only two waves appear at the upper surface, but the heat source located at the centre with optimum height causes the entire cavity to have maximum heat transfer performance. The current problem is solved to benefit the installation of microelectronic cooling of a water-to-air heat exchanger or a pin-fin MHS heat transfer media.

Numerical Investigation of the nanofluid mixed convection on two layers enclosure with rotating cylinder: High Darcy Number Effects

The present study, numerically investigated of mixed convection in a square enclosure with two layers, with Al2O3–water nanofluid (upper layer) and nano-porous medium (lower layer) with an adiabatic rotating circular cylinder at the center of the enclosure. The top and bottom walls are assumed adiabatic, while the left sidewall is heated, and the right sidewall kept cooled. Numerically, COMSOL code based on the Galerkin finite element method used for solved the dimensionless governing equations. The non-dimensional parameters that used in this study are: Rayleigh number (Ra) ranged from 103 up to 106, Darcy number (Da) equal to 10−3, the angular rotational velocity (Ω) ranged (0 and 6000), the solid volume fraction (ɸ=0.06), and the inner circular cylinder radius as (R = 0.2). The results showed that when Rayleigh numbers increase, a noticeable increase in the flow intensity and the steep temperature gradient, while the values increase when the cylinder rotates. The value of the local Nusselt number was high in the upper half of the cavity. The effect of the cylinder rotates is greater on the value of the local Nusselt number when using the low Rayleigh Numbers.

Nonlinear mixed convective nanofluid flow about a rough sphere with the diffusion of liquid hydrogen

In this paper, a study of steady nonlinear mixed convective nanoliquid flow about a rough sphere with the diffusion of liquid hydrogen is considered. The governing equations are first modelled from the current physical problem, and then, suitable non-similar transformations are applied to non-dimensionalize the model equations. The resultant nonlinear dimensionless equations are linearized by using the Quasilinearization technique. The resulting linear system of differential equations are approximated by finite differences to obtain numerical solutions. The impacts of different physical parameters involved in the problem, such as the distribution of velocity, temperature, nanoparticle volume fraction and species concentration are studied. The analysis of wall gradients is carried out, which discusses the skin friction, heat and mass transfer rates defined at the surface of the sphere. The graphs of numerical results are plotted, which reveal that the flow velocity is increased, while the fluid temperature is reduced, for increasing values of the roughness parameter. The presence of mixed convection parameter delays the occurrence of separation in the boundary layer in both the cases of an ordinary fluid and a nanofluid. For increasing values of the Schmidt number, the species concentration decreases, while the rate of mass transfer increases. Moreover, the thermophoresis parameter of the nanofluid increases the fluid's temperature, while it decreases the heat transfer rate. The fluid's temperature reduces for larger values of nonlinear convection parameter. Also, the flow velocity increases for the diffusion of liquid hydrogen.

Mixed convection nanofluid flow in a non-Darcy porous medium with variable permeability: entropy generation analysis

The study discusses the issue of entropy generated in a mixed convection Cu–water nanofluid flow in an inclined channel filled with a non-Darcy porous medium with variable permeability taking into account the Navier slip and convection at the boundary. The equations of momentum and temperature are highly nonlinear and coupled, and these are solved using the homotopy analysis method after converting to the dimensionless form. The flow velocity and temperature expressions as required during the entropy generation analysis are obtained. Bejan number is also obtained which indicates the role of heat transfer and viscous dissipation in the entropy generation process. The consequences of the relevant flow parameters are discussed, and the results are shown graphically. It was observed that entropy is minimum just above the center of the channel width.

A comparative study of γAl2O3–C2H6O2 and γAl2O3–H2O near a vertical curved surface having porous medium

The present analysis reveals the impact of porous medium and mixed convection nano-fluid flow near an exponentially curved surface. For this purpose alumina is treated as nano-particles along with two base fluids such as H2O and C2H6O2. Under different assumptions the mathematical model of energy and momentum equations are developed by using curvilinear coordinates. The PDEs are transformed into non-linear differential equations by using similarity transformation variables. The table of skin friction and Nusselt number are drawn by fluctuating the values of different parameters for both fluids. Moreover, the numerical solutions are generated in MATLAB by using Bvp4c. Influence of effective and without effective Pr numbers for an incompressible γAl2O3−C2H6O2 and γAl2O3−H2O are investigated. We observe that the velocity profile increases for increasing values of curvature, mixed convection and volume fraction of nanoparticles for two different cases effective and with-out effective Prandtl numbers. Moreover, in case of effective Pr number, the temperature profile decreases but for with-out effective Pr number temperature profile increases. Furthermore, the graphs are drawn to check the behavior various parameters for effective and with-out effective Pr numbers.

Mixed convection of nanofluid in a square enclosure with a hot bottom wall and a conductive half‐immersed rotating circular cylinder

AbstractIn this study. The mixed convection in a square enclosure with a hot bottom wall and a conductive half‐immersed rotating cylinder from its top wall is investigated numerically. The enclosure is filled with a copper‐water nanofluid. The upper half of the cylinder is cooled by the surrounding air, whereas its solid lower half is exposed to the nanofluid. The two left and right sidewalls of the enclosure, together with the remaining regions of its top wall, are assumed to be adiabatic. The dimensionless governing equations are expressed for the velocity and the temperature formulation, and they are modeled by using COMSOL code based on the Galerkin finite element method. In the present work, the geometrical aspect ratio is considered to be varied as (0.2 ≤ R/L ≤ 0.5), the thermal conductivity ratio is considered to be varied as 1 ≤ Kr ≤ 10, the angular rotational velocity is considered to be varied as 0 ≤ ≤ 1000, and the ambient convection heat transfer coefficient is considered to be varied as 5 ≤ h ≤ 20. However, the solid volume fraction (ϕ), the Prandtl number (Pr), and the Rayleigh number (Ra) are considered to be fixed at ϕ = 0.02, Pr = 6.2, and Ra = 105. It was found that the convection effect becomes more pronounced when the angular rotational velocity increases, whereas a reverse behavior is observed with an increase in the geometrical aspect ratio. Also, it was observed that the heat explorer depth begins to decrease as the angular rotational velocity increases until the increases of angular rotational velocity effect is diminishing therefore it may be the main target of the present research. This observation is seen for both considered values of the thermal conductivity ratio and the geometrical aspect ratio. Moreover, it was observed that both the local and the average Nusselt numbers increase as the geometrical aspect ratio increases. A comparison with a previously published numerical work is performed, and a good agreement between the results is observed.

Combined effects of double rotating cones and magnetic field on the mixed convection of nanofluid in a porous 3D U-bend

Impacts of double rotating cone system and magnetic field on mixed convection in a 3D U-shaped porous channel are analyzed with finite element method. Impacts of different influencing parameters such as Richardson number (between 0.05 and 50), Hartmann number (between 0 and 100), rotational speed of the cones (between −5000 and 5000), size of the cones (between 0 and 0.075H) and aspect ratio (between 0.4 and 2) on the flow and heat transfer are scrutinized. It was revealed that the average Nu decreases when higher values of Richardson number, magnetic field strength are considered while the impact is reverse for angular speed, size and aspect ratio of the cones. The hot walls of the U-channel contribute to overall heat transfer differently and the variation is significant for different pertinent parameters. The average Nu of hot wall near the exit is reduced by about 20% at the highest Richardson number. The magnetic field reduced the effective convention while significant increment of the average Nusselt number of the bottom wall is observed with higher size and speed of the rotating cones. The size effect is influential in the case of rotation and up to 143% increment in the average Nu is attained for the highest size with highest speed of the cones while this amount is only 9.5% for a stationary cone. Enhancements up to 84% in the average Nu is obtained with rotation of the cones while aspect ratio contributed to only 10% increment. A multi-parametric POD analysis for the evaluation of local and average Nusselt numbers of the hot surfaces of the U-shaped cavity is performed. The number of modes required to represent the data in the parametric space is 20, 20 and 48 for left, right and bottom surfaces.

Influence of an inclined stretching cylinder over MHD mixed convective nanofluid flow due to chemical reaction and viscous dissipation

AbstractThis paper analyzed the steady two‐dimensional magnetohydrodynamic mixed convective viscous nanofluid and heat transfer toward an inclined stretching cylinder with chemical reaction and uniform magnetic field. The governing partial differential equation in a cylindrical form is reduced to a set of nonlinear ordinary differential equations by using appropriate similarity transformation and solved numerically by spectral quasilinearization methods (SQLMs). A new approach of this method is employed to derive numerical expressions for velocity, temperature, and concentration profile. The convergence and accuracy of our numerical scheme are observed. The SQLM is employed to find out the convergent series solution. There is an increase in the temperature profiles due to the increase in the thermophoresis parameter. The increase in effective Eckert number results in the increase of the temperature profile.

Nonlinear mixed convective nanofluid flow along moving vertical rough plate

The objective of the current research paper is to investigate the effects of surface roughness on magnetohydrodynamic nonlinear mixed convection nanofluid flow over vertically moving plate. The highly coupled dimensional nonlinear partial differential equations (NPDE) are converted into dimensionless NPDE along with the boundary conditions with the help of non-similar transformations. The resulting set of dimensionless nonlinear PDE’s are solved by using Quasilinearization technique and implicit finite difference method. Impacts of various dimensionless parameters, namely, Brownian diffusion (Nb), nonlinear mixed convection ( ), nanoparticle buoyancy ratio (Nr), Lewis number (Le), thermophoresis (Nt), frequency (n), magnetic (M) and small parameter ( ) are studied in detail on profiles as well as gradients. The results reveal that increasing values of increase the velocity profile, while increasing values of Nr decrease the same. Further, increasing values of and n exhibit sinusoidal variations on skin-friction coefficient, heat and nanoparticle mass transfer rates. Moreover, the presence of nonlinear mixed convection parameter has significant effects on fluid flow compared to its absence. In addition to this, rate of heat transfer is analyzed in presence and absence of nanoparticles.

Numerical Differential Quadrature Examination of Steady Mixed Convection Nanofluid Flows Over an Isothermal Thin Needle Conveying Metallic and Metallic Oxide Nanomaterials: A Comparative Investigation

The significance of the local skin friction as well as the heat transfer rate on the motion of water $$ \left( {{\text{H}}_{2} {\text{O}}} \right) $$ and ethylene glycol $$ \left( {{\text{C}}_{2} {\text{H}}_{6} {\text{O}}_{2} } \right) $$ conveying metallic and metallic oxide nanoparticles (e.g., Al, Cu, Zn, Al203, CuO and ZnO) along a vertical thin needle is needed to improve the performance of chemical reactors, heat exchangers, pharmaceutical equipment and hybrid-powered engines. This led to the investigation of mixed convection flow and heat transfer of some nanofluids, in which the thermal conductivity and viscosity vary nonlinearly with the volume fraction. For simplifying the present investigation, appropriate variables were introduced successfully in the mathematical formulation to convert the governing nonlinear partial differential equations to coupled ordinary differential equations (ODEs). Moreover, the resulting ODEs were solved numerically via a robust differential quadrature algorithm. Furthermore, a comparative study with the existing literature is found to be in an excellent agreement. The enhancement of heat transfer in nanofluids is ascertained by increasing the convection ratio. Generally, the maximum improvement in the local skin friction was perceived for the flows of zinc–water-based nanofluids ( $$ {\text{Zn}} $$ – $$ {\text{H}}_{2} {\text{O}} $$ ) with the upsurge in the volume fraction of the nanoparticles $$ {\text{Zn}} $$ . On the contrary, the highest enhancement in the heat transfer rate was revealed for the flows of copper–ethylene glycol-based nanofluids ( $$ {\text{Cu}} $$ – $$ {\text{C}}_{2} {\text{H}}_{6} {\text{O}}_{2} $$ ) with the increase in the weight percent of the $$ {\text{Cu}} $$ nanomaterial loading.

MHD mixed convective nanofluid flow about a vertical slender cylinder using overlapping multi-domain spectral collocation approach

This paper investigates the magnetohydrodynamic flow, heat and mass transfer characteristics in a silver water nanofluid about a vertical slender cylinder by considering diffusion-thermal, thermo-diffusion, chemical reaction and Hall effects. The nonlinear partial differential equations modelling the flow problem are non-dimensionalized and the overlapping multi-domain bivariate spectral quasilinearisation method is used to solve the dimensionless equations. The impact of flow parameters on the fluid properties and physical quantities of interest are determined. Amongst other findings, we found that increment in the nanoparticle volume fraction, Hall current and curvature parameter augments the skin friction coefficient and diminishes the heat transfer rate, while the introduction of chemical reaction, silver nanoparticles, Hall current and Soret effect into the system enhances the mass transfer rate. Also, the fluid properties amplifies in the curved surface than in the flat plate.

Progress on numerical simulation of nanofluids: impact of an isothermal spherical partition on the mixed convection of nanofluids within cubic enclosures

The main objective of our work is to light out the three-dimensional flow of an Ag-water nanofluid within a lid-driven cubical space which equipped with a spherical heater into its center. Due to its crucial role in the characterization of the main transfer within such configurations, impact of some parameters is widely inspected. It consists the Richardson value (0,05 to 50), the solid volume fraction (0% to 10%), as well as the heater geometry (10% ≤ d ≤ 25%). To do so, a numerical code based on the Lattice-Boltzmann method, coupled with a finite difference one, is used. The latter has been validated after comparison between the present results and those of the literature. It is to note that the three dimensions D3Q19 model is adopted based on a cubic Lattice, where each pattern of the latter is characterized by nineteen discrete speeds.

MIXED CONVECTION NANOFLUID FLOW OVER A VERTICAL WEDGE SATURATED IN A POROUS MEDIUM WITH INFLUENCE OF DOUBLE DISPERSION USING LIE GROUP SCALING

The article reflects the influence of double dispersion on mixed convection nanofluid flow over a vertical wedge saturated in porous medium. The governing higher order nonlinear partial differential equations are nondimensionalized via Lie group scaling analysis, and the gained similarity equations are solved numerically through the spectral quasi-linearization method using the Gauss-Lobatto collocation points. The appropriate results are reported here, to introduce the impact of Lewis number, buoyancy ratio, mixed convection, thermal dispersion, Brownian motion, solutal dispersion, and thermophoresis parameters on velocity, temperature, and nanoparticle volume fraction profiles, graphically. The heat and mass transfer coefficients are listed in tabular form. To verify the accuracy of present computations, residual analysis study is also depicted.

Second law analysis for mixed convection nanofluid flow in an inclined channel with convectively heated walls

AbstractIn this study, entropy generation analysis for Cu–water nanofluid mixed convective flow in an inclined channel occupied with a saturated porous media with Navier slip and convective boundary conditions is explored. The governing equations composed of equations of velocity and temperature are nondimensionalized and then solved utilizing the technique of homotopy analysis. Temperature and velocity profile expressions are acquired, which are then used to calculate the entropy produced in the scheme. The impacts of the corresponding fluid parameters are addressed in‐depth on velocity, temperature, entropy generation, Bejan number, Nusselt number, skin friction, volume flow rate, and heat carried out by the fluid for nanofluid concentration. Entropy has been observed to be minimal in all cases just above the channel center and maximum at the channel's bottom wall. Fluid friction‐generated entropy has been discovered to have a higher influence on entropy generation. We also provide a comparative study with existing literature to validate our current results.

Effects of surface roughness on mixed convective nanofluid flow past an exponentially stretching permeable surface

A numerical study is carried out to display the effects of surface roughness on mixed convective nanofluid flow along an exponentially stretching surface in presence of suction/injection. The dimensional coupled nonlinear partial differential equations are transformed into dimensionless form by using suitable non-similar transformations. The resulting equations are solved by utilizing the Quasilinearization technique as well as the implicit finite difference scheme. The influence of several non-dimensional parameters on various profiles and gradients is examined. The results are presented graphically, which are analyzed to depict the effects of various physical parameters, for example, Brownian diffusion parameter Nb, thermophoresis parameter Nt, suction/blowing parameter A and Lewis number Le. In order to analyse the influence of surface roughness on mixed convective nanofluid flow, the major part of this research paper is devoted to investigate the effects of the small parameter α and frequency parameter n over the gradients defined at the wall. The results reveal that an increase in the values of Nb and Nt, enhances the velocity and temperature of the fluid. The increasing value of suction parameter (A > 0) reduces the velocity of the fluid. Further, the increasing values of Nb and Le decrease the nanoparticle volume fraction profile. The sinusoidal variations are observed in the skin-friction coefficient, Nusselt number as well as the nanoparticle Sherwood number. Moreover, with the addition of nanoparticles, the magnitude of the skin-friction coefficient increases, while the magnitude of heat transfer rate decreases, significantly.

Diffusion of liquid hydrogen in time-dependent MHD mixed convective flow

An innovative study on liquid hydrogen diffusion in time-dependent mixed convection flow is carried out in the presence of magnetic field effects. In fact, this is the first approach to analyze such flow problems, and also this is the first research paper to study the non-uniform heat sink/source and nonlinear chemical reaction in the presence of liquid hydrogen diffusion. Initially, the governing equations are reduced to dimensionless form by using non-similar transformations and are linearized by applying quasilinearization technique. Then, the finite difference approximation is utilized to discretize the resulting equations. The mixed convection is analyzed along with exponentially stretching surface through various graphs on profiles as well as gradients. The results display that the non-uniform heat source parameter increases the fluid velocity as well as temperature, and the magnetic parameter reduces the friction at the wall. Specifically, the skin friction coefficient decreases about 40% in the presence of magnetic field. The mass transfer rate increases for high-order chemical reaction and for destructive chemical reaction rate. The mass transfer rate is found to be high for the diffusion of liquid nitrogen than that for the diffusion of liquid hydrogen. In fact, the mass transfer rate increases about 22% for the diffusion of liquid nitrogen. This study can assist the design engineers who are working in pertain to the diffusion of liquid gases in mixed convection regimes. Also, the obtained data in the present study can be more useful for future investigations about time-dependent mixed convection nanofluid flow problems.

Entropy generation and nanofluid mixed convection in a C-shaped cavity with heat corner and inclined magnetic field

A numerical simulation of entropy generation due to MHD mixed convective of water-copper nanofluid in a C-shaped cavity with a heated corner is performed. The cavity is subjected to an inclined uniform magnetic field, and the top wall of the cavity is adiabatic and moves with a constant velocity. The governing equations are formulated by employing the single-phase nanofluid approach and the resulting equations have been solved by the Finite Volume Method (FVM). Impacts of the pertinent parameters on the fluid flow and heat transfer inside the cavity have been presented graphically. The numerical data have been plotted in the portrait of streamlines, isotherms and the average Nusselt numbers. The effects of volume fraction, Hartmann number, and the aspect ratio on the entropy generation and mixed convection of the C-shaped cavity are investigated. It is found that for an aspect ratio = 0.1, increasing the nanofluid volume fraction causes an increment in the heat transfer. At low volume fractions and Hartmann numbers, the outcomes manifest a better thermal performance. Generally, the rate of entropy generation increases by increasing both the Hartmann number and the volume fraction.