Solid Volume Fraction Of Nanoparticles Research Articles

MHD mixed convection of nanofluid due to an inner rotating cylinder in a 3D enclosure with a phase change material

PurposeThe purpose of this study is to numerically examine the mixed convection of CuO-water nanofluid due to a rotating inner hot circular cylinder in a 3D cubic enclosure with phase change material (PCM) attached to its vertical surface. Heat transfer and fluid flow characteristics were examined for various values of pertinent parameters.Design/methodology/approachFinite element method was used in the numerical simulation. Influence of various pertinent parameters such as Rayleigh number (between 10$^5$ and 10$^6$), Hartmann number (between 0 and 100), angular rotational speed of the cylinder (between −50 and 50), solid nanoparticle volume fraction (between 0 and 0.04) and PCM parameters (height-between 0.2H and 0.8H, thermal conductivity ratio- between 0.1 and 10) on the convective heat transfer characteristics are numerically studied.FindingsIt was observed that local heat transfer variations along the hot surface differ significantly for the cases with and without magnetic field where three distinct hot spots of peak Nusselt number are established when magnetic field is imposed. The average Nusselt number enhancement with the nanofluid at the highest particle volume fraction is 52.85 per cent at Hartmann number of 100, whereas its value is 39.76 per cent for the case in the absence of magnetic field. When the inner cylinder rotates, flow and thermal fields are affected within the cavity. The local heat transfer variations spread over the hot surface with cylinder rotation and 16.43 per cent of reduction in the average heat transfer is obtained with counter-clockwise rotation at 100 rad/sec. An enhancement in the PCM height and a reduction in the thermal conductivity of the PCM result in average heat transfer deterioration for the 3D cavity. The amount of the reduction is 43 per cent when the PCM height is increased from 0.2H to 0.8H, whereas 19.10 per cent enhancement in the heat transfer is achieved when thermal conductivity ratio (PCM) to the base fluid is increased from 0.1 to 10.Originality/valueSuch configurations can be designed for convection control, and in our case, various methods are available. Some of the investigated methods can be used in applications where magnetic field already exists. Convection control study in 3D cavity gives more realistic results as compared to 2D configurations, and results of the current investigation may be used for the design, optimization and flow control of many thermal applications involving magnetic field effects.

Entropy generation in flow of ferromagnetic liquid with nonlinear radiation and slip condition

Here, flow of magnetite nanoliquid by nonlinear stretching sheet is considered. Heat source/sink and nonlinear radiation are explored. Velocity and thermal slip aspects in Fe3O4-nanoliquid flow modelling are retained. Present study focuses on entropy generation analysis. Viscous dissipation, non-linear thermal radiation and joule heating irreversibilities are accounted. Formulated problems computed by Optimal Homotopy algorithm. The velocity, temperature, entropy generation, Bejan number, skin friction and heat transfer rate are discussed. It is observed that entropy generation rates enhances for Brinkman number and solid volume fraction of nanoparticles while reverse behavior of Bejan number holds.

MHD Natural Convection Ferrofluid Flow in Semi-Annulus Enclosures

This study examines the natural convection flow and the heat transfer of a water-based ferrofluid consisting Fe3O4 nanoparticles in a semi-annulus cavity with a circular outer and sinusoidal inner walls under the effect of a magnetic field produced by multiple nodal magnetic sources. The equations governing the ferrofluid flow are numerically solved using the dual reciprocity boundary element method. That is the equations are transformed into integral equations only on the boundary by using the fundamental solution of the Laplace equation and treating all other terms as nonhomegeneity through radial basis function approximation, which results in a discretized system of small size. The numerical computations are performed for several physical parameters namely, Hartmann, Rayleigh and magnetic numbers, solid volume fraction of nanoparticles, the number of undulation and the amplitude of sinusoidal wall. The obtained results show that increasing Rayleigh number, solid volume fraction and amplitude of sine waves enhance the average Nusselt number whereas it decreases with an increase in Hartmann number.

Lattice Boltzmann study of multi-walled carbon nanotube (MWCNT)-Fe3O4/water hybrid nanofluids natural convection heat transfer in a Π-shaped cavity equipped by hot obstacle

In the present paper, the effect of nanofluid and the hot obstacle in a Π-shaped cavity is investigated. Lattice Boltzmann method is used to simulate the fluid flow and heat transfer. The effects of the parameters such as the nanoparticle solid volume fraction, the Rayleigh number, aspect ratio of cavity and hot obstacle position on the flow pattern and heat transfer parameters are studied. The numerical results are compared with previous results for validation, and a good agreement obtained. It is found that the average Nusselt number is increased by increasing the nanoparticle solid volume fraction, the Rayleigh number and the aspect ratio of cavity. Moreover, the effect of Rayleigh number on the average Nusselt number at high Rayleigh numbers (105–106) is more pronounced than that at low Rayleigh numbers (103–104) due to the different heat transfer mechanisms. The position of the hot obstacle affects the heat transfer significantly. When the hot obstacle is located on the center, the heat transfer is more effective.

Exploring ferrofluids for heat transfer augmentation

Abstract We explore the potential of ferrofluids for heat transfer augmentation, via numerical simulations using water-based ferrofluids flowing between parallel plates (laminar flows; Reynolds number (Re) 〈1 0 0), exposed to external magnetic fields, produced by single and multiple magnetic line dipoles. Two water-based ferrofluids having different magnetic and thermo-physical properties owing to their different solid volume fractions of magnetic nanoparticles are considered. It is shown that the presence of the non-uniform magnetic field produced by the dipoles induces an attractive magnetic body force on ferrofluids, which disturbs the flow locally, thus augmenting local Nusselt number. While flow strongly gets affected by the magnetic field at Re = 25, magnetic field does not affect the flow significantly beyond Re ≥ 75 which shows the dominance of inertial forces over magnetic forces, at a given external magnetic field strength. A detailed parametric study is performed to investigate the effect of single and multiple dipole placements, the solid volume fraction of magnetic nanoparticles and Reynolds number on heat transfer enhancement. It is concluded that forced convective heat transfer can be enhanced by applying external magnetic field compared to no magnetic field case, only under certain boundary conditions.

Forced Convection of Pulsating Nanofluid Flow over a Backward Facing Step with Various Particle Shapes

In this study, numerical analysis of forced convective pulsating nanofluid flow over a backward-facing step with different nanoparticle shapes was performed by the finite volume method. The effects of the Strouhal number (between 0.1 and 2), solid nanoparticle volume fraction (between 0 and 0.04) and nanoparticle shapes (spherical, blade and cylindrical) on the heat transfer and fluid flow were examined with the aid of numerical simulation. It was observed that the average Nusselt number is a decreasing function of the Strouhal number for the considered range, and it enhances for higher solid particle fractions. Using nanofluids with spherical particles is advantageous in pulsating flow, whereas cylindrically-shaped particles are preferred in steady flow configurations. Average Nusselt number enhancements up to 30.24% and 27.95% are achieved with cylindrical- and spherical-shaped particles at the highest volume fraction.

Heat transfer by natural convection of Fe3O4-water nanofluid in an annulus between a wavy circular cylinder and a rhombus

Researchers in modern science always attempt to find new techniques to optimize the performance of energy devices through heat transfer enhancement. It comes to the knowledge that such enhancement can be done with the help of nanofluids. Therefore, the present study is aimed to investigate the role of natural convection and thermal radiation on thermo-hydrodynamics of nanofluid heat transfer in an annulus between a wavy circular cylinder and a rhombus enclosure subject to a uniform magnetic field. A new model for viscosity called magnetic field dependent (MFD) viscosity is used. Mathematical formulation of the current physical model is based on the continuity, momentum and energy equations. Numerical simulation of the reduced problem is done with the help of Control Volume based Finite Element Method (CVFEM). The impacts of controlling physical parameters, for instance, Rayleigh number, radiation parameter, Hartmann number, aspect ratio, shape factor of nanoparticles and solid volume fraction of nanoparticles on thermo-hydrodynamics of flow are studied. The quantities of physical interest are graphically presented and discussed in detail. From the present study it becomes apparent that the local heat transfer rate decreases with an increase in aspect ratio in the absence of Hartmann number. In addition, for decreasing values of aspect ratio, the space for fluid flow inside enclosure becomes wider.

Numerical study of MHD nanofluid natural convection in a baffled U-shaped enclosure

In this study, nanofluid natural convection in a baffled U-shaped enclosure in the presence of a magnetic field is investigated. Lattice Boltzmann method (LBM) is used to study present problems. KKL (Koo-Kleinstreuer-Li) correlation is applied to calculate the effective thermal conductivity and viscosity of nanofluid. The effect of the Brownian motion on the effective thermal conductivity is considered in this correlation. The combination of the four topics (nanofluid, U-shaped enclosure, baffle, magnetic field) is the main novelty of the present study. Effect of Rayleigh number, Hartmann number, nanoparticle volume fraction and cavity aspect ratio on the flow field and heat transfer characteristics have been investigated. The results demonstrate that the average Nusselt number increases by increments of the Rayleigh number, nanoparticle solid volume fraction and aspect ratio. However, the rate of heat transfer is suppressed by the magnetic field. The effect of magnetic field on heat transfer is more significant at higher Rayleigh number and the effect of Ra on the average Nusselt number is more noteworthy at lower Ha. Besides, the effect of Rayleigh number on heat transfer enhancement becomes more significant at higher aspect ratio.

Effects of nanoparticles to present a statistical model for the viscosity of MgO-Water nanofluid

In this paper, the rheological behavior of MgO-Water nanofluid at different temperatures ranging from 25 °C to 60 °C and different volume fractions ranging from 0.07% to1.25% has been examined. Suspensions were prepared by dispersing MgO nanoparticles in Water. Viscosities were measured at the different shear rate range of 6.115 s−1 to 73.38 s−1. Results showed that the base fluid exhibits Newtonian behavior and the nanofluid samples exhibit a non-Newtonian behavior. The obtained results also showed that the viscosity increases with an increase in the solid volume fraction of nanoparticles and decreases with increasing temperature. Finally, the findings were compared with famous models and it was found that these models can not able to explain this nanofluid behavior and doesn't have reasonably excellent agreement.

Nonlinear Rosseland thermal radiation and energy dissipation effects on entropy generation in CNTs suspended nanofluids flow over a thin needle

In this paper, we examine thermal radiation effect of the nonlinear form on the dissipative nanofluids containing carbon nanotubes past a moving horizontal thin needle. We also perform a second law analysis with viscous dissipation. Single-wall carbon nanotube and multiple-wall carbon nanotube drop in H_{2}O base fluid. Introducing suitable dimensionless variables, we reduce the governing equations to self-similar nonlinear differential equations. Matlab in-built boundary value solver bvp4c and shooting method are applied for the solution of the reduced set of self-similar differential equations. The numerical results thus obtained are compared, which agree well with respect to desired accuracy. Various graphs are depicted and illustrate qualitatively the influence of flow controlling parameters such as Eckert number, heating parameter, radiation parameters, nanoparticles solid volume fraction, and size of thin needle on entropy generation, temperature distribution, and Bejan number.

Natural convection in a CuO–water nanofluid filled cavity under the effect of an inclined magnetic field and phase change material (PCM) attached to its vertical wall

In this study, natural convection of CuO–water nanofluid in a square cavity with a conductive partition and a phase change material (PCM) attached to its vertical wall is numerically analyzed under the effect of an uniform inclined magnetic field by using finite element method. Effects of various pertinent parameters such as Rayleigh number (between $$10^5$$ and $$10^6$$ ), Hartmann number (between 0 and 100), magnetic inclination angle (between $$0^{\circ}$$ and $$90^{\circ}$$ ), PCM height (between 0.2H and 0.8H), PCM length (between 0.1H and 0.8H), thermal conductivity ratio (between 0.1 and 100) and solid nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and thermal characteristics were numerically analyzed. It was observed that when magnetic field is imposed, more reduction in average Nusselt number for water is obtained as compared to nanofluid which is $$31.81\%$$ for the nanofluid at the highest particle volume fraction. The average heat transfer augments with magnetic inclination angle, but it is less than $$5\%$$ . When the height of the PCM is increased which is from 0.2H to 0.8H, local and average Nusselt number reduced which is $$42.14\%$$ . However, the length of the PCM is not significant on the heat transfer enhancement. When the conductivity ratio of the PCM to the base fluid within the cavity is increased from 0.1 to 10, $$29.5\%$$ of the average Nusselt number enhancement is achieved.

CFD analysis of thermal and hydrodynamic characteristics of hybrid nanofluid in a new designed sinusoidal double-layered microchannel heat sink

In this study, laminar and steady flow of hybrid Al2O3–Cu/water nanofluid is done for volume fraction of solid nanoparticles 0–2% in a double-layered microchannel with sinusoidal walls. The results of this study show that the sinusoidal shape of the microchannel walls has a strong effect on increasing heat transfer, and increasing solid nanoparticle volume fraction in base fluid can have a significant difference for increasing Nusselt number, so that the value of Nusselt number for solid nanoparticles volume fraction of 2% for Re = 50, 300, 700 and 1200 experiences 23%, 22% 19% and 13% increase compared with the base fluid. By increasing fluid viscosity, the shear stress especially in the areas close to wall and in fluid layers is increased and this factor can increase pressure drop in higher solid nanoparticles volume fractions. The static temperature profiles are affected by hot surfaces and their sinusoidal shapes in lower Reynolds numbers, and the curve for temperature of flow centerline for Re = 700 and 1200 is straight lines. Therefore, the usage of it for Reynolds numbers above 700 is not recommended.

NUMERICALSTUDY OF MIXED CONVECTION FLOWIN ALID

A numerical investigation of steady laminar mixed convection flow of a Copper-water nanofluid in a lid –driven cavity has been executed. In the present study, the left vertical and inclined walls are heated at constant temperature while the right vertical and inclined right walls are maintained at constant cold temperature. The bottom wall is adiabatic and moving with uniform velocity. The study has been carried out for Rayleigh number Ra= 104– 106, Reynolds number Re=20-100 and solid volume fraction of Cu nanoparticles Ø= 0-0.05. The effective viscosity and thermal conductivity of the nanofluid have been calculated by Brinkman and Maxwell-Garnett models, respectively. The results indicated that, the Nusselt number increases with increasing Ra, Re and Ø.

Simulation of nanofluid natural convection in a U-shaped cavity equipped by a heating obstacle: Effect of cavity's aspect ratio

Abstract Research on nanofluid for heat transfer enhancement of thermal systems has received great attention owing to the lack of energy sources. In this study, fluid flow and natural convection heat transfer of Al2O3–Water or TiO2–water nanofluid inside a U-shaped cavity consist of a hot obstacle has been investigated numerically by lattice Boltzmann method (LBM). In this paper, different parameters are investigated such as Rayleigh number, the solid volume fraction of the nanoparticles, the U-shaped cavity's aspect ratio and heating obstacle's height on the flow field and heat transfer in the enclosure. The results showed that the Rayleigh number (Ra), cavity aspect ratio (AR) and obstacle's height can be affected on isotherms, streamlines and local and average Nusselt number. The average Nusselt number of the obstacle sides increased by increasing the Ra number and solid volume fraction of nanoparticles (ϕ) regardless the AR. In addition, by increasing the AR, the average Nusselt number increased. At low Ra, the effect of nanoparticles on increment of heat transfer for narrow cavities was more than wide ones.

Numerical analysis and ANFIS modeling for mixed convection of CNT-water nanofluid filled branching channel with an annulus and a rotating inner surface at the junction

Numerical study for mixed convection of CNT-water nanofluid flow in a branching channel with annulus at the junction and a rotating surface was performed by using finite volume method. This geometry can be used in a variety of engineering applications such as in geothermal, gas pipelines, in pharmaceutical, fuel cells and many others. The numerical simulations are performed for various values of pertinent parameters such as Richardson number, angular rotational velocity of the inner surface at the annulus junction, solid nanoparticle volume fraction and diameter of the inner rotating. It was observed that the recirculation regions established within the annulus and separated fluid zones on the walls of the branching channel near the junction are strongly influenced by the by rotation of the inner surface at the annulus. The average Nusselt number enhancements up to 64% are obtained for the nanofluid containing the highest particle volume fraction for Ri = 0.01 and Ri = 1 when the inclination angle of the lower branching channel is 45°. Finally, ANFIS modeling technique with triangular-shaped membership function and 48 fuzzy rules are used to predict the average Nusselt numbers for the hot walls of the channel and annulus part.

Numerical investigation of MHD effects on nanofluid heat transfer in a baffled U-shaped enclosure using lattice Boltzmann method

Lattice Boltzmann method (LBM) was carried out to investigate the effects of magnetic field and nanofluid on the natural convection heat transfer in a baffled U-shaped enclosure. The combination of different specifications of the baffle, LBM, nanofluid and magnetic field is the main innovation in the present study. In order to consider the effect of Brownian motion on the thermal conductivity, Koo–Kleinstreuer–Li model is used to define thermal conductivity and viscosity of nanofluid. Effects of Rayleigh number, Hartmann number, nanoparticle volume fraction, height and position of the baffle on the fluid flow and heat transfer characteristics have been examined. It was found that raising the Rayleigh number and nanoparticle solid volume fraction leads to increase the average Nusselt number irrespective of the position of the hot obstacle. However, the heat transfer rate is suppressed by the magnetic field. The heat transfer enhancement by introducing nanofluid decreases as increasing Rayleigh number, but it increases as increasing the Hartmann number. Moreover, the maximum heat transfer rate was observed when the enclosure equipped with a baffle with (s, h) = (0.2, 0.3) or (0.4, 0.3).

Effect of MWCNT–Fe3O4/water hybrid nanofluid on the thermal performance of ribbed channel with apart sections of heating and cooling

A two-dimensional (2D) numerical simulation is performed to simulate the laminar forced convection of a nanofluid in a ribbed channel with apart heating (cooling) sources using lattice Boltzmann method (LBM). The multi-walled carbon nanotubes–iron oxide nanoparticles/water hybrid nanofluid (MWCNT–Fe3O4/water hybrid nanofluid) is used in this simulation. The velocity field, temperature distribution and heat transfer rate are numerically analyzed with the streamlines and isotherm patterns employing of a house code. In addition, the effect of Reynolds number (Re = 25, 50, 75 and 100), nanoparticle solid volume fraction (ϕ = 0, 0.001, 0.003) and ratio of the blocks height (A = 0.2, 0.3, 0.4) are measured. The results are validated against the results reported in the literature, and a good agreement is reported. The obtained results show a maximum value of 16.49% increase in the average heat transfer coefficient for all the considered cases relative to the base fluid. Moreover, the local Nusselt number proves that the use of blocks on the channel walls can increase the amount of heat transfer. Finally, the average Nusselt number shows a linear dependence on the increasing ratio of blocks height for constant solid volume fraction. The results of this study apply to the industrial equipment heating and cooling applications.

Convective–radiative heat transfer in a cavity filled with a nanofluid under the effect of a nonuniformly heated plate

PurposeThe purpose of this study is to examine the radiation effect on the natural convective heat transfer of an alumina–water nanofluid in a square cavity in the presence of centered nonuniformly heated plate.Design/methodology/approachThe square cavity filled with alumina–water nanofluid has a nonuniformly heated plate placed horizontally or vertically at its center. The plate is heated isothermally with linearly varying temperature. The vertical walls are cooled isothermally with a constant temperature, while the horizontal walls are insulated. The governing equations have been discretized using finite volume method on a uniformly staggered grid system. Simulations were carried out for different values of the heated plate nonuniformity parameter (λ = –1, 0 and 1), the nanoparticles solid volume fraction (Φ = 0.01 − 0.04) and the radiation parameter (Rd = 0 – 2) at the Rayleigh number of Ra = 1e+07.FindingsIt is found that the total heat transfer rate is enhanced with an increase in the radiation parameter for both the horizontal and vertical plates. The role of nanoparticles addition to the base fluid can have dual effects on the heat transfer rate by augmenting and dampening for the absence of radiation while it dampens the heat transfer rate for the presence of radiation.Originality/valueThe originality of this work is to analyze steady natural convection in a square cavity filled with a water-based nanofluid in the presence of centered nonuniformly heated plate. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids, and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

Effect of viscous dissipation on MHD water-Cu and EG-Cu nanofluids flowing through a porous medium

This paper provides a comparative analysis of two different types of nanofluids for Stokes second problem. Additional effects of MHD, porosity and viscous dissipation are also considered. Two types of Newtonian liquids (water and ethylene glycol) are considered as base fluids with suspended nanosized Cu particles. A homogenous model of Newtonian nanofluids over a flat plate is used to describe this phenomenon with Stokes boundary conditions such that the ambient fluid is static and with uniform temperature. The problem is first written in terms of nonlinear partial differential equations with physical conditions; then after non-dimensional analysis, the Laplace transform method is used for its closed-form solution. Exact expressions are determined for the dimensionless temperature, velocity field, Nusselt number and skin friction coefficient and arranged in terms of exponential and complementary error functions satisfying the governing equations and boundary conditions. They are also reduced to the known solutions of Stokes second problem for Cu-water nanofluids. Results are computed using Maple software. The results showed that both skin friction and rate of heat transfer increase with increasing solid volume fraction of nanoparticles. MHD and porosity had an opposite effect on velocity for both types of nanofluids. The dimensionless temperature increases by increasing the Eckert and Hartmann numbers.

Simultaneous impacts of MHD and variable wall temperature on transient mixed Casson nanofluid flow in the stagnation point of rotating sphere

A numerical analysis is provided to scrutinize time-dependent magnetohydrodynamics (MHD) free and forced convection of an electrically conducting non-Newtonian Casson nanofluid flow in the forward stagnation point region of an impulsively rotating sphere with variable wall temperature. A single-phase flow of nanofluid model is reflected with a number of experimental formulae for both effective viscosity and thermal conductivity of nanofluid. Exceedingly nonlinear governing partial differential equations (PDEs) subject to their compatible boundary conditions are mutated into a system of nonlinear ordinary differential equations (ODEs). The derived nonlinear system is solved numerically with implementation of an implicit finite difference procedure merging with a technique of quasi-linearization. The controlled parameter impacts are clarified by a parametric study of the entire flow regime. It is depicted that from all the exhibited nanoparticles, Cu possesses the best convection. The surface heat transfer and surface shear stresses in the x - and z -directions are boosted with maximizing the values of nanoparticle solid volume fraction φ and rotation λ . Besides, as both the surface temperature exponent n and the Casson parameter γ upgrade, an enhancement of the Nusselt number is given.