Ahmed Kadhim Hussein

Boundary layer flow and heat transfer due to permeable stretching tube in the presence of heat source/sink utilizing nanofluids

The present study aims to identify effects due to uncertainties of thermal conductivity and dynamic viscosity of nanofluid on boundary layer flow and heat transfer characteristics due to permeable stretching tube in the presence of heat source/sink. Water-based nanofluid containing various volume fractions of different types of nanoparticles is used. The nanoparticles used are Cu, Ag, CuO, and TiO2. Four models of thermal conductivity and dynamic viscosity depending on the shape of nanoparticles are considered. The results are presented to give a parametric study showing influences of various dominant parameters such as Reynolds number, the suction/injection parameter, solid volume fraction of nanoparticles, type of nanoparticles, the heat generation/absorption parameter and skin friction coefficient. The results indicate that the skin friction coefficient decreases as the Reynolds number and the suction/injection parameter (γ) increase, while the local Nusselt number increases as the Reynolds number and the suction/injection parameter (γ) increase. The results are compared with another published results and it found to be in excellent agreement.

Effects of Movable-Baffle on Heat Transfer and Entropy Generation in a Cavity Saturated by CNT Suspensions: Three-Dimensional Modeling

Convective heat transfer and entropy generation in a 3D closed cavity, equipped with adiabatic-driven baffle and filled with CNT (carbon nanotube)-water nanofluid, are numerically investigated for a range of Rayleigh numbers from 103 to 105. This research is conducted for three configurations; fixed baffle (V = 0), rotating baffle clockwise (V+) and rotating baffle counterclockwise (V−) and a range of CNT concentrations from 0 to 15%. Governing equations are formulated using potential vector vorticity formulation in its three-dimensional form, then solved by the finite volume method. The effects of motion direction of the inserted driven baffle and CNT concentration on heat transfer and entropy generation are studied. It was observed that for low Rayleigh numbers, the motion of the driven baffle enhances heat transfer regardless of its direction and the CNT concentration effect is negligible. However, with an increasing Rayleigh number, adding driven baffle increases the heat transfer only when it moves in the direction of the decreasing temperature gradient; elsewhere, convective heat transfer cannot be enhanced due to flow blockage at the corners of the baffle.

Mixed Convection in a Lid-Driven Two-Dimensional Square Cavity with Corner Heating and Internal Heat Generation

The aim of the numerical study is to investigate the mixed convection flow and heat transfer in a square lid-driven cavity with corner heating and internal heat generation or absorption. The top wall of the cavity is moving at a constant speed in its own plane. A portion of the left and bottom walls of the cavity are kept at a constant temperature; that is, the heaters are fixed at the left bottom corner of the cavity. The right wall is maintained at lower temperature and the remaining portions of the cavity are insulated. The finite volume method is used to discretize the governing equations that are then solved iteratively. The results are obtained for different lengths of the heaters, Richardson numbers, and internal heat generation or absorption parameters. It is observed that the heat transfer rate is enhanced at forced convection dominated regime when the vertical length of the heater is higher than that of the horizontal length.

Inclination effects of magnetic field direction in 3D double-diffusive natural convection

In this paper a numerical study which treats the effect of the magnetic field inclination on 3D double diffusive convection in a cubic cavity filled with a binary mixture is presented. The two vertical walls are maintained at different temperatures and concentrations. A particular interest is reserved to determine the effect of the magnetic field inclination on the flow structure and heat and mass transfer. The problem is formalized based on the vector potential vorticity procedure in its three-dimensional configuration and discretized based on the finite volume method. The results are given for Ra?=?105, Pr?=?1 and Le?=?2. This paper presents respectively the inclination effects of the magnetic field direction on the three-dimensional flow structure and on heat and mass transfer. The main results show that the increase of the inclination of the magnetic field direction damped the flow. A critical angle, which depending on Hartmann number, caused big change on the flow structure and accented the three dimensional aspect in the cavity.

Numerical analysis of steady natural convection of water in inclined square enclosure with internal heat generation

Laminar natural convection in a two-dimensional inclined square enclosure has been numerically studied using finite volume method. The research deals with the investigation of the effect of Prandtl number and inclination angle on the stream contours and isotherms in this enclosure where the left side wall is maintained at isothermal hot temperature, while the opposite side wall is maintained at isothermal cold temperature. The other top and bottom walls are considered thermally insulated. The enclosure in the present work is based on the geometry of Tofiqul Islam et al. [9], (2007) which is considered inclined with inclination angles ranging from 0° to 30° and filled with water as a working fluid where its Prandtl number is taken as 6. All the numerical calculations are performed at the external Rayleigh numbers 103 and 106 while the internal Rayleigh numbers ranging from 105 to 108. The results are presented as a streamline and isotherm plots as well as the variation of the average Nusselt numbers at the hot wall are also presented. The results show a good confidence with other published results.

Investigation of thermal and optical performance of a phase change material–filled double-glazing unit:

Phase change material applied in the glazing structure can improve its thermal performance, which has effect on its optical performance. A model to determine thermal and optical performance of a phase change material–filled double-glazing unit was developed, and the effect of optical parameters of phase change material was numerically investigated. The results show that the effect of the refractive index of phase change material on temperature time lag, temperature decrement factor, solar transmittance, solar absorptance, and reflectance of a phase change material–filled double-glazing unit is weak when the refractive index of phase change material is lower than 1.95; however, the effect of the extinction coefficient of phase change material is violent. The liquid phase change material with large extinction coefficient is not recommended from the viewpoint of light utilization, but the large extinction coefficient of solid phase change material is accepted from the viewpoint of energy utilization.

Analytical and numerical study on convection of nanofluid past a moving wedge with Soret and Dufour effects

Purpose The purpose of this study is to investigate the Soret and Dufour effects on the double-diffusive convective boundary layer flow of a nanofluid past a moving wedge in the presence of suction. Design/methodology/approach The similarity transformation is applied to convert the governing nonlinear partial differential equations into ordinary differential equations. Then, they are solved numerically by the fourth-order Runge–Kutta–Gill method along with the shooting technique and the Newton–Raphson method. In addition, the ordinary differential equations are also analytically solved by the homotopy analysis method. Findings The results for dimensionless velocity, temperature, solutal concentration and nanoparticle volume fraction profiles, as well as local skin friction coefficient and local Nusselt and local Sherwood numbers are presented through the plots for various combinations of pertinent parameters involved in the study. The heat transfer rate increases on increasing the Soret parameter and it decreases on increasing the Dufour parameter. The mass transfer behaves oppositely to heat transfer. Practical implication In engineering applications, a wedge is used to hold objects in place, such as engine parts in the gate valves. A gate valve is the valve that opens by lifting a wedge-shaped disc to control the timing and quantity of fluid flow into an engine. Originality/value No such investigation is available in literature, and therefore, the results obtained are novel.