In this study, free convection heat transfer in a concentric annulus between a cold square and heated elliptic cylinders in presence of magnetic field is investigated. The square and elliptic cylinders are maintained at uniform temperatures and it is assumed that the walls are insulating magnetic field. Lattice Boltzmann method is applied to solve the governing equations. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The numerical investigation is carried out for different governing parameters namely; the Hartmann number, Rayleigh number and nanoparticle volume fraction. Also a correlation of Nusselt number corresponding to active parameters is presented. The results reveal that average Nusselt number is an increasing function of nanoparticle volume fraction and Rayleigh number, while it is a decreasing function of Hartmann number. Moreover it can be found that the enhancement in heat transfer increases as Hartmann number increases but it decreases with increase of Rayleigh number.
In this paper, ferrofluid flow and heat transfer in a semi annulus enclosure is investigated considering thermal radiation. The enclosure has a wall with constant heat flux boundary condition. Combined effects of Ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) are considered. It is assumed that the magnetization of the fluid is varying linearly with temperature and magnetic field intensity. Control Volume based Finite Element Method (CVFEM) is applied to solve the governing equations. The calculations were performed for different governing parameters namely; the Radiation parameter, Rayleigh number, nanoparticle volume fraction, Magnetic number arising from FHD and Hartmann number arising from MHD. Results show that Nusselt number is an increasing function of Rayleigh number, nanoparticle volume fraction, magnetic number while it is a decreasing function of with Hartmann number and radiation parameter.
Control Volume Finite Element Method (CVFEM) is a new approach in which all advantages of finite volume method and finite element method are combined together. In this research, CVFEM is employed to simulate the impact of radiative heat transfer on magnetohydrodynamic free convection of water based nanofluid. Fe3O4– H 2 O ferrofluid has been used and viscosity of nanofluid is variable respect to magnetic field. Roles of the radiation parameter R d , numbers of undulations N , Fe3O4–water volume fraction ϕ , Hartmann number H a and the Rayleigh number R a are depicted. Nu a v e is present as a formula according to effect of various parameters. Results prove that the inner surface temperature decreases with the augment of buoyancy forces. Nu a v e enhances with the augmentation of the thermal radiation parameter while it decreases with the augment of H a and N .
No abstract is provided for this article.
Influence of Lorentz forces and radiative term on nanoparticles treatment through a porous semi annulus has been displayed in current article. An innovative numerical method was employed to portray the roles of radiative term, Rayleigh number and Lorentz forces. Working fluid is Al2O3-H2O nanofluid with various shapes. Results display that inner wall temperature reduces with rise of Rd. The best shape of nanoparticle in view of hydrothermal treatment is Platelet shape.
No abstract is provided for this article.
In this paper, condensing pressure drop of refrigerant-based nanofluid inside a tube is studied. Isobutene was selected as the base fluid while CuO nanoparticles were utilized to prepare nano-refrigerant. However, for the feasibility of nanoparticle dispersion into the refrigerant, Polyester oil (POE) was utilized as lubricant oil and added to the pure refrigerant by 1% mass fraction. Various values of mass flux, vapor quality, concentration of nanoparticle are investigated. Results indicate that adding nanoparticles leads to enhance frictional pressure drop. Nanoparticles caused larger pressure drop penalty at relatively lower vapor qualities which may be attributed to the existing condensation flow pattern such that annular flow is less influenced by nanoparticles compared to intermittent flow regime.
In this paper magnetohydrodynamics nanofluid hydrothermal treatment in a cubic cavity heated from below is presented. The mathematical model consists of continuity and the momentum equations, while a new model is proposed to see the effects Brownian motion on the effective viscosity and thermal conductivity of nanofluid. The Lattice Boltzmann method is utilized to simulate three dimensional problems. The Koo–Kleinstreuer–Li correlation is also taken into account. Numerical calculation is made for different values of Hartmann number, nanoparticle volume fraction and Rayleigh number. The results are presented graphically in terms of streamlines, isotherms and isokinetic energy as well as Nusselt number. It is observed that the applying magnetic field results in a force opposite to the flow direction that leads to drag the flow and then reduces the convection currents by reducing the velocities. Also it can be concluded that Nusselt number is an increasing function of Rayleigh number and nanofluid volume fraction while it is a decreasing function of Hartmann number.
A two-dimensional numerical study has been performed to investigate natural convection in a square cavity with curve boundaries filled with Cu–water nanofluid. Lattice Boltzmann Method (LBM) is used to simulate this problem. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. This investigation was compared with other numerical methods and was found to be in excellent agreement. Effects of nanoparticle volume fraction, Rayleigh numbers and inclination angle on flow and heat transfer are considered. The results proved that the change of inclination angle has a significant impact on the thermal and hydrodynamic flow fields. Also it can be found that maximum values of enhancement are obtained at Ra =103 and Ra =105 for γ >0° and γ <0°, respectively.
In the framework of this paper, nanofluid flow and heat transfer in a square enclosure containing a rectangular heated body is investigated computationally. The fluid in the cavity is a water-based nanofluid containing four different types of metal and metal-oxide nanoparticles: alumina (Al2O3), copper (Cu), silver (Ag) and titania (TiO2). The effective viscosity and thermal conductivity of the nanofluid are calculated by the Brinkman model and Maxwell–Garnett (MG), respectively. The Lattice Boltzmann Method (LBM) has been adopted to solve this problem. The effects of various governing parameters such as nanofluid type, Rayleigh number, volume fraction of nanoparticles and height of the rectangular heated body contained in the cavity on hydrothermal characteristics are studied. The results indicate that both the Nusselt number and dimensionless entropy generation are increasing functions of the Rayleigh number and nanoparticle volume fraction of the nanofluid. Furthermore, the effect of nanoparticle volume fraction is found to be more pronounced for a low Rayleigh number as compared to a high Rayleigh number. Excellent accuracy is achieved with the LBM code.
In this work, three dimensional flow of a fluctuating nanofluid is examined in moving (rotating) coordinates. Carbon nanotubes (multi-wall carbon nanotubes (MWCNTs)/single-wall carbon nanotubes (SWCNTs)) are taken as nanoparticles whereas water is considered as the base fluid. Xue's model for effective thermal conductivity (carbon nanotube based composite) is utilized. Entropy generation is analyzed in the presence of both homogeneous and heterogeneous mass concentrations. The dimensionless variables are introduced to obtain the dimensionless form of the boundary layer equations along with the entropy augmentation equation. Equations are then solved using an explicit scheme based on the finite differences, and the behaviour of the entropy augmentation, Bejan number and temperature is elaborated. The effects of various dimensionless parameters such as Reynolds number, Brinkman number and radiation parameter on the entropy augmentation rate, and Bejan number are presented graphically for MWCNTs and SWCNTs. Variation in the engineering coefficients (Nusselt number, skin friction, Sherwood number) are shown with various emerging parameters for MWCNTs and SWCNTs. It is found that the entropy augmentation rate can be controlled by minimizing the action of the Brinkman and Reynolds numbers. The results also reveal that the heat transfer (rate) is bigger for SWCNTs in relation to MWCNTs.
Radiative nanomaterial thermal behavior within a permeable closed zone with elliptic hot source is simulated. Darcy law is selected for simulating permeable media in existence of magnetic forces. Contour plots for various buoyancy, Hartmann numbers and radiation parameter were illustrated. Carrier fluid is Al2O3-water with different shapes. Outputs prove that conduction mode augments with enhance of Ha. Nu augments with considering radiation source term.
