Khaled Al-Salem

Mhd mixed convection with joule heating effect in a lid-driven cavity with a heated semi-circular source using the finite element technique

A computational fluid dynamics simulation of heat transfer characteristics on the conjugate effect of Joule heating and magnetic field acting normal to the lid-driven cavity with a heated semi-circular source on one wall under constant temperature is investigated. The left wall of the cavity moves in an upward (case I) or downward (case II) direction, and buoyancy forces are also effective. Horizontal walls are adiabatic. The governing mass, momentum, and energy equations along with boundary conditions are expressed in a normalized primitive variables formulation. The finite element method is used in the solution of the normalized governing equations. The study is performed for pertinent parameters such as the Rayleigh number, Hartmann number, and Joule heating parameter. It is found that the average Nusselt number can be decreased with the increasing of the Rayleigh number in the presence of Joule effect. The magnetic field can be a good control parameter for heat transfer and fluid flow.

Effects of inclination angle on natural convection in an inclined open porous cavity with non‐isothermally heated wall

Purpose – The purpose of this numerical study is to investigate the effects of inclination angle and non‐isothermal wall boundary conditions in a partially open cavity filled with a porous medium.Design/methodology/approach – In this study, the governing dimensionless equations were written using Brinkman‐Forchheimer model. They are numerically solved by using finite volume method with SIMPLE solution algorithm by applying open boundary conditions in one side. The opposed side of the open cavity is under non‐isothermal boundary conditions.Findings – Results are presented by streamlines, isotherms, velocity and temperature profiles as well as the local and mean Nusselt numbers for different values of the governing parameters such as Grashof numbers, porosity, amplitude of sinusoidal function and inclination angle of the cavity. It is found that inclination angle is the most important parameter on the temperature and flow field.Originality/value – The originality of this study is the open sided enclosure fi...

Numerical study of three-dimensional combined buoyancy and thermocapillary convection and evaluation of entropy generation

Purpose – The main purpose of this paper is to conduct on three-dimensional buoyancy and thermocapillary convection in an enclosure. Entropy generation is obtained from the calculated values of velocities and temperatures. Design/methodology/approach – As numerical method, the vorticity-vector potential formalism allows, in a three-dimensional configuration, the elimination of the pressure, which is a delicate term to treat. The control volume finite difference method is used to discretize equations. The central-difference scheme for treating convective terms and the fully implicit procedure to discretize the temporal derivatives are retained. The grid is uniform in all directions with additional nodes on boundaries. The successive relaxation iterating scheme is used to solve the resulting non-linear algebraic equations. Findings – Results are presented via entropy generation due to heat transfer, entropy generation due to fluid friction and total entropy generation. It is found that Marangoni number beco...

Effects of magnetic field and viscous dissipation on entropy generation of mixed convection in porous lid-driven cavity with corner heater

Purpose – The purpose of this paper is to investigate the effects of magnetic field and viscous dissipation on mixed convection heat transfer, fluid flow and entropy generation in a porous media filled square enclosure heated with corner isothermal heater. Design/methodology/approach – Finite volume method has been used to solve governing equations. A code is developed by FORTRAN and entropy generation is calculated from the obtained results of velocities and temperature. Results are presented via streamlines, isotherms, local and mean Nusselt number for different values of Richardson number (0.001=Ri=100), Hartmann number (0.001=Ha=100), Darcy number (0.001=Da=0.1), length of heaters (0.25=hx=hy=0.75) and viscous dissipation factors (10−4=e=10−6). Findings – It is observed that entropy is generated mostly due to lid-driven wall and right side of the heater. Entropy generation decreases with increasing of Hartmann number and heat transfer increases with decreasing of viscous parameter. Originality/value –...

Turbulent flow and heat transfer enhancement of forced convection over heated baffles in a channel

Purpose – The purpose of this paper is to examine the turbulent fluid flow and heat transfer characteristics for rectangular channel provided with solid plate baffles which are arranged on the bottom and top channel walls in a periodically staggered way.Design/methodology/approach – The turbulent governing equations are solved by a finite volume method with the second‐order up winding scheme and the k‐ω turbulence model to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (semi‐implicit method for pressure‐linked equation) algorithm. The parameters studied include the entrance Reynolds number Re (5.103‐2.104), the baffles height are fixed at (h=0.08 m); whereas three different baffle spacing were considered S1 = D, S2 = D/2 and S3=3D/2 and the working medium is air.Findings – In this work, it is found that vortex shedding generated by the baffle on the upper wall can additionally enhance heat transfer along the baffle surfaces. The wavy flow signi...

Effect of uniform inclined magnetic field on natural convection and entropy generation in an open cavity having a horizontal porous layer saturated with a ferrofluid

ABSTRACT Numerical analysis of natural convection combined with entropy generation in a square open cavity partially filled with a porous medium has been performed for a ferrofluid under the effect of inclined uniform magnetic field. Governing equations with corresponding boundary conditions formulated in dimensionless stream function and vorticity using Brinkman–extended Darcy model for porous layer have been solved numerically using finite difference method. An influence of key parameters on ferrofluid flow and heat transfer has been analyzed. It has been found that an inclusion of spherical ferric oxide nanoparticles can lead to a diminution of entropy generation in the case of similar flow and heat transfer structures.

Unsteady analysis of natural convection in a carbon nanotube-water filled cavity with an inclined heater

ABSTRACT A finite element solution has been performed in this work to solve unsteady governing equations of natural convection in a carbon nanotube–water-filled cavity with inclined heater. The temperature of ceiling and left vertical walls is lower than that of the heater while the other walls are adiabatic. The main governing parameters are nanofluid volume fraction and Rayleigh number (Ra). It is found that the heat transfer rate shows different trends based on Rayleigh number and it increases with increase in nanoparticle volume fraction. It has been estimated that average Nusselt number (Nu) is dependent onRa through power regression models with strong positive linear correlation between ln (Nu) and ln (Ra). In particular, for the maximum time, when the solid volume fraction is varied from 0 to 0.1 the dependence between average Nu and linear Ra, on a logarithmic scale, is very high.

Numerical analysis of effect of magnetic field on combined surface tension and buoyancy driven convection in partially heated open enclosure

Purpose – The purpose of the paper is to investigate the effects of magnetic field on the flow driven by the combined mechanism of buoyancy and thermocapillary flow in an open enclosure with localized heating from below and symmetrical cooling from the sides. Design/methodology/approach – The governing equations are discretized by the control volume method with power-law scheme and solved numerically by SIMPLE algorithm for the pressure-velocity coupling together with under-relaxation technique. Findings – In this work, it is observed that, the average Nusselt number, decreases with an increase of Hartmann number Ha, and increases with increase of Prandtl and Grashof number. At large Marangoni number Ma, a prominent secondary eddies are observed at the top of the enclosure due to the effect of surface tension. Originality/value – The study combines many external forces on thermocapillary flow.

Heat transfer enhancement of turbulent flow in a channel with diamond shaped baffles

A numerical study was conducted on turbulent flow in a rectangular duct with diamond shaped baffles placed on the top and bottom walls. The governing equations, based on the low Reynolds number k-e model, are solved to describe the thermohydraulic behaviour of the fluid using the finite volume method. Velocity profiles and drag coefficient were obtained and presented for selected locations along the duct, namely, upstream, downstream and between the two diamond shaped baffles. The results were compared with available experimental and numerical data from literature. The highest value of the normalised Nusselt number was attained when the baffles were tilted five degrees from the vertical.

MHD heat transfer and entropy generation in inclined trapezoidal cavity filled with nanofluid: Numerical investigation and sensitivity analysis

Purpose The main purpose of this paper is to define 2D numerical study and a sensitivity analysis of natural convection heat transfer and entropy generation of Al2O3-water nanofluid in a trapezoidal cavity, with considering of the presence of a constant axial magnetic field. Design/methodology/approach The effects of the three effective parameters, the Rayleigh number, Hartmann number (Ha) and also inclination angle on the heat transfer performance and entropy generation, are investigated using a finite volume approach. The sensitivity analysis of the effective parameters is done utilizing the response surface methodology. Findings The results obtained showed that the mean Nusselt number and total entropy generation increase with the Rayleigh number. Also, increasing the inclination angle reduces the mean Nusselt number (regardless of the magnetic field). In addition, it is found that the mean Nusselt number increases until Ha = 10 and then decreases by increasing of Ha number, regardless of the inclination angle. The sensitivity of the mean Nusselt number to the Ha number and inclination angle α is negative. It is concluded that to maximize the mean Nusselt number and minimize the entropy generation, simultaneously, the Ha and inclination angle must be 50° and 0°, respectively. Originality/value There is no published research in the literature about sensitivity analysis of magneto-hydrodynamic heat transfer and entropy generation in inclined trapezoidal cavity filled with nanofluid.