In this article, two-dimensional laminar-forced convection nanofluids flow over a stretching surface in a porous medium has been studied.The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved numerically by the fourth order Runge-Kutta integration scheme featuring a shooting technique.Different models of nanofluid based on different formulas for thermal conductivity and dynamic viscosity are used.Different types of nanoparticles as copper, silver, alumina and titanium Oxide with water and Ethylene glycol as their base fluids has been considered.The influence of significant parameters such as nanoparticle volume fraction, kind of nanofluid, Magnetic parameter and Reynolds number on the flow and heat transfer characteristics is discussed.The influence of significant parameters such as Thermal conductivity parameter, volume fraction of the nanoparticles, Permeability parameter, suction/injection parameter and Velocity ratio parameter on the flow and heat transfer characteristics is discussed.It was found that choosing Titanium oxide as the nanoparticle and Ethylene glycol as base fluid proved to have the highest cooling performance for this problem.
No abstract is provided for this article.
No abstract is provided for this article.
Current article presents a numerical investigation for three dimensional turbulent flow using the MCRT method to simulate solar radiations as a heat flux and the finite volume method in Ansys Fluent to simulate the equations. The fluid in absorber is a synthetic oil having eight hundred index mixed with Aluminium Oxide nanoparticles to enhance the heat transfer process. The study comparing different cases, including different numbers of longitudinal fins assembled inside the absorber with two arrangements and three particular Reynolds number in addition to the testing concentration ratio of the heat flux using the MCRT method. The impact of using three different numbers of fins (2, 4 and 6) at two different arrangements ("a" and "b") were presented. The three Reynolds number used was (18600, 23000 and 28000). Two Rim angles of the collector are tested (80o) and (120o), results showed that (120º) was achieved high outlet temperature with a concentration ratio (CR=82.47). The effects on outlet temperature, friction factor, Nusselt number, and then on the performance evaluation criterion (PEC) of the absorber tube were displayed. The results of the study proved that using nanofluid and finned absorber can increase the absorber hydrothermal performance and using (6) fins of arrangement "b" shows better performance in terms of heat transfer than arrangement "a".
In this study magnetohydrodynamic effect on free convection of nanofluid in an eccentric semi-annulus filled is considered. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. Lattice Boltzmann method is applied to simulate this problem. This investigation compared with other works and found to be in excellent agreement. Effects of the Hartmann number, nanoparticle volume fraction, Rayleigh numbers and position of the inner circular cylinder on flow and heat transfer characteristics are examined. Also a correlation of Nusselt number corresponding to active parameters is presented. The results show that Nusselt number has direct relationship with nanoparticle volume fraction and Rayleigh number but it has inverse relationship with Hartmann number and position of inner cylinder at high Rayleigh number. Also it can be concluded that heat transfer enhancement increases with increase of Hartmann number and decreases with augment of Raleigh number.
Fe3O4–water nanofluid flow in a cavity with constant heat flux is investigated using a control volume based finite element method (CVFEM). Effects of Rayleigh and Hartmann numbers and volume fraction of Fe3O4 (nano-magnetite, an iron oxide) on flow and heat transfer characteristics are analyzed. Results indicate that the temperature gradient is an increasing function of the buoyancy force and the volume fraction of Fe3O4, but it is a decreasing function of the Lorentz force. Also, the rate of heat transfer is augmented with an increase in the Lorentz force. However, the opposite is true on the rate of heat transfer with the buoyancy force. Furthermore, the core vortex moves downward with an increase in the Lorentz force. It is expected that the results presented here will not only provide useful information for cooling of electronic components but also complement the existing literature.
This article employs mesoscopic approach to investigate CuO-H2O nanofluid inside a cavity with hot obstacle. Influence of magnetic field is retained. Lattice Boltzmann method (LBM) is selected as simulation tool. Brownian motion impact is added in model of nanofluid. Roles of Reynolds number (Re), CuO-H2O nanofluid volume fraction (ϕ), Darcy number (Da) and Hartmann number (Ha) are demonstrated. Results reveal that thermal plume diminishes with augment of (Ha). Convective mode improves with the increase of Da and Re. It is observed that temperature gradient is an increasing function of Hartmann number.
In this chapter the control volume finite element method is applied to solve two important kinds of problems, namely, lid-driven cavity and natural convection. The governing equations of fluid motion and heat transfer in their vorticity stream function form are used to simulate the fluid flow and heat transfer. Boundary conditions are introduced and applied in FORTRAN code. The results using the FORTRAN code are compared with previous results. These comparisons illustrate excellent agreement between the present calculations and previously published results. The calculations were performed for different governing parameters. The geometry used to solve natural convection equations is a cylinder with a sinusoidal wall in it.
Nanofluid forced convection heat transfer is simulated in presence of electric field. The bottom wall is lid driven and considered as positive electrode. The working fluid is Fe3O4-ethylene glycol nanofluid. Control volume based finite element method is selected to obtain the results which are the roles of volume fraction of Fe3O4 (ϕ), Reynolds number (Re) and supplied voltage (Δφ). Electric field dependent (EFD) viscosity of nanofluid according to previous experimental data is taken into account. Results indicate that Coulomb force helps the convective mode so temperature gradient enhances by enhancing Coulomb force. Enhancing in temperature gradient due to existence of electric field is highest at low Reynolds number.
Control volume based finite element method (CVFEM) is applied to simulate H2O based nanofluid radiative and convective heat transfer inside a porous medium. Non-Darcy model is employed for porous media. Influences of Hartmann number, nanofluid volume fraction, radiation parameter, Darcy number, number of undulations and Rayleigh number on nanofluid behavior were demonstrated. Thermal conductivity of nanofluid is estimated by means of previous experimental correlation. Results show that Nusselt number enhances with augment of permeability of porous media. Effect of Hartmann number on rate of heat transfer is opposite of radiation parameter.
This paper aims to present complete analytic solution to boundary layer flow through a porous medium over a stretching porous wall. Homotopy Analysis Method (HAM) has been used to get accurate and complete analytic solution. The analytic solutions of the system of nonlinear ordinary differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. The validity of our solutions is verified by the numerical results (fourth-order Runge-Kutta).The temperature profiles are shown and the influence of Reynolds number, wall injection/suction parameter, Prandtl number, power of temperature/heat flux distribution are discussed in detail. Then effects of effective parameters on Nusselt number are investigated.
Latent Heat Thermal Energy Storage Systems (LHTESS) which work based on energy storage and retrieval during solid-liquid phase change is used to establish balance between energy supply and demand. The main restriction for these systems is the weakness of thermal conductivity of common PCMs. Different enhancement methods is applied to LHTESS in order to overcome this problem. In present work, the method of adding nanoparticles to pure PCM and making Nano-Enhanced Phase Change Material (NEPCM) and using Y-shaped fin with suitable array are applied to accelerate solidification process. The two mentioned methods are analyzed separately. The effects of nanoparticles volume fractions on solidification rate are studied and geometry parameters, which are fin branch angle, length and thickness, are changed to find the best fin array. Copper particles and water are used as nanoparticles and PCM, respectively. Aluminum Y-shaped fin system is implemented in LHTESS. The numerical approach which is used in this paper is Standard Galerkin Finite Element Method. In this work, Y-shaped fin structure has been employed in order to enhance the performance of LHTESS during discharging process, also the efficiency of nanoparticle dispersion in PCM and adding fin with different structures on LHTESS performance have been studied from the viewpoint of either discharging expedition or maximum energy storage capacity. Also, adaptive grid refinement is used in numerical procedure which are proposed as the novelties here. Results indicate that by considering both parameters of full solidification time and maximum energy storage capacity, applying Y-shaped fin with suitable array demonstrates better enhancement in comparison to adding nanoparticles.
Unsteady turbulent magnetohydrodynamic nanofluid hydrothermal treatment is studied. The zero-equation turbulence model is used to simulate turbulent flow. The modeling results obtained by applying the hybrid differential transformation method–finite difference method to solve this problem confirm its viability. An analytical procedure is used for finding the effects of the problem parameters. Results indicate that the average Nusselt number over the lower plate depends linearly on volume fraction of nanofluid, Hall parameter, turbulent Eckert number, and Reynolds number whereas it is inversely proportional on the Hartmann number and the turbulent parameter.
Nanofluid heat transfer intensification in a porous enclosure in existence of magnetic field is studied numerically using Non-Darcy model. Simulation has been done by means of CVFEM. Viscosity of Fe3O4-water is considered as a function of magnetic field. Roles of Darcy number ( D a ) , inclination angle ( ξ ) , Fe3O4-water volume fraction ( ϕ ) , Hartmann ( H a ) and Rayleigh ( R a ) numbers are demonstrated in outputs. Results illustrate that Nuave increases with increase of Ra and Darcy numbers. Isotherms become denser near the hot surface with augment of inclination angle and Darcy number. Temperature gradient reduces with augment of Habut it enhances with rise of inclination angle.
Impact of Lorentz forces on CuO–water nanofluid flow in a permeable enclosure is presented by means of CVFEM. Darcy’s law is applied for porous media. In order to predict properties of nanofluid, KKL model has been utilized. Important parameters are inclination angle ( ξ = 0 ∘ to 90°), CuO–water volume fraction ( ϕ = 0 and 0.04), Hartmann ( Ha = 0 to 20) and Rayleigh ( Ra = 1 0 2 , 250 and 103) numbers for porous medium. A formula for Nu ave is provided. Results demonstrated that Nusselt number detracts with enhancement of ξ , Ha . Heat transfer augmentation detracts with rise of buoyancy forces but it enhances with rise of inclination angle and Hartmann number.
To investigate natural convection heat transfer in a semi-annulus enclosure filled with nanofluid, the Control Volume based Finite Element Method (CVFEM) is used. The fluid in the enclosure is Cu–water nanofluid. The inner and outer semi circular walls are maintained at constant temperatures while the two other walls are thermally insulated. The Navier Stokes equations in their vorticity-stream function form are used to simulate the flow pattern and isotherms. The numerical investigation is carried out for different governing parameters namely; the Rayleigh number, nanoparticle volume fraction and the angle of turn for the enclosure. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell–Garnetts (MG) and Brinkman models, respectively. The results reveal that there is an optimum angle of turn in which the average Nusselt number is maximum for each Rayleigh number. Moreover, the angle of turn has an important effect on the streamlines, isotherms and maximum or minimum values of local Nusselt number.
In recent years the effect of magnetic field and porous medium in different engineering applications such as the cooling of reactors and many metallurgical processes involves the cooling of continuous tiles has been more considerable. And also, in several engineering processes, materials manufactured by extrusion processes and heat treated materials traveling between a feed roll and a wind up roll on convey belts possess the characteristics of a moving continuous surface, oil industry and combustion, penetration etc., you can find some applications of Magnetohydrodynamic and porous medium. Although in previous chapters some examples were presented, which contained these two important topics, but in this separate chapter some other examples are discussed due to its importance in the following sections: 6.1 Introduction 6.2 Magnetohydrodynamic Couette Fluid Flow Between Parallel Plates 6.3 Micropolar Fluid in a Porous Channel 6.4 Magnetohydrodynamic Viscous Flow Between Porous Surfaces
Many phenomena are existed in the environment in which particle's motion can be observed on them, such as centrifugation, centrifugal filters, industrial hopper, etc. Surface of the motion has different shapes especially for rotating application; it can be a circular, parabolic, or conical surface. It's necessary for scientists to analyze the motion of the particles on these surfaces, so an analytical solution is usually the more preferred method in engineering area because of less computational and high accuracy. Some of them are introduced in these sections: 7.1 Introduction 7.2 Motion of a Spherical Particle on a Rotating Parabola 7.3 Motion of a Spherical Particle in Plane Couette Fluid Flow 7.4 Nonspherical Particle Sedimentation 7.5 Motion of a Spherical Particle in a Fluid Forced Vortex 7.6 Combustion of Microparticles 7.7 Unsteady Sedimentation of Spherical Particles 7.8 Transient Vertically Motion of a Soluble Particle
