Browsing by Author "Abdelmadjid Chehhat"
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Item CFD Modeling of Thermophysical Properties Influence on The Heat Transfer in Metal Foam Heat Sinks(2018) Abdelmadjid ChehhatThis study presents a CFD simulation by COMSOL multiphysics software of a metal foam heat sink used for cooling electronic power component. The simulation is a transient 3D of air laminar flow through a channel equipped with a plate-electronic component system cooled by a metal foam heat sink. The goal is to determine the thermohydraulic behavior of the system. The foam heat sink is considered as a porous medium, the Darcy-Forchheimer-Brinkman model is used. We discussed the effects of air velocity, heat flux dissipated by the electronic device and the type of metal foam on the system phenomenology.Item Comportement non-orthotrope d’une tôle asymétrique(2018) Abdelmadjid ChehhatAu cours du laminage, les tôles peuvent présenter des états de déformations différents d’une couche à une autre de sorte que les surfaces (les peaux) en contact avec les cylindres du laminage subissent des cisaillements simples suivant la direction de laminage. On parle alors de symétrie monoclinique prismatique qui consiste à considérer 2 composantes de textures ayant d’inégales fractions volumiques et qui admettent respectivement le plan (DL, DN) et l’axe DT comme plan et axe de symétrieItem Numerical simulation of convective heat losses in a helical tube of a cylindrical solar receiver Simulation numérique des pertes thermiques par convection dans un tube hélicoïdal d’un récepteur solaire cylindrique(2018-06-27) Abdelmadjid Chehhatn this paper, natural convection heat losses in a cylindrical solar receiver are investigated numerically. The study is conducted using three helical tube diameters: 12mm, 16mm and 25mm. The diameter of the receiver is 0.3 m with an aspect ratio equal to one and three aperture ratios of 1, 0.75 and 0.5. In each case, the receiver tube inside the cylindrical cavity is modelled by a helical spiral similar to those of real systems. The simulations are performed for three inlet temperatures (of 50, 75 and 100°C) and four receiver tilt angles (of 0, 30, 60 and 900) with a constant mass flow rate of 0.0885 kg/s. The effects of some parameters such as receiver size, boundary conditions, tube diameter, receiver tilt, inlet temperature and opening ratio on convective heat losses and outlet temperature are presented in form of graphs. It has been found that the convective heat losses are reduced by using the adiabatic boundary condition imposed on the half-circumference of the tube. Thus, increasing the helical tube diameter causes an increasing in the convective heat losses. The increasing of the fluid temperature and the opening ratio are found proportional to the increasing of convective heat losses.Item Numerical simulation study on the heat transfer of a spiral tube receiver designed to a thermal power tower.(2013-05-17) Abdelmadjid Chehhatin this work the heat transfer of a spiral tube receiver exposed to concentrated solar radiation is studied theoretically. The simulations were performed using Fluent6.3.26 for two different sections at several Reynolds numbers: 100, 300, 500, 700, and 1000 to see the effect of the inlet velocity on the outlet temperature. The effect of the inlet temperature is also discussed by varying the inlet temperature of the water of 293K to 313K. The results show that the average temperature of the heating and adiabatic surface (inner wall) is decreasing when the velocity inlet is increasing. The outlet temperature of a semicircular section is higher than that of the circular section, but the Nusselt number of this one is twice higher as that of semicircular section and it’s due to the geometrical shape of the section.Item Numerical Study of Natural Convection in Square Tilted Solar Cavity Considering Extended Domain(2018) Abdelmadjid ChehhatThis work presents a numerical investigation on heat transfer and fluiddynamic aspects for a solar open cavities in an extended fluid flow domain. The vertical wall inside the open cavities facing the aperture is assumed to be isothermal while the other walls are kept insulated. Heat transfer steady laminar natural convection is studied by solving the non-dimensional governing equations of mass, momentum and energy in the framework of a finite volume method. The analysis are carried out under Rayleigh number range of 9.41×105 to 3.76×106, inclination 0° to 90° and opening ratio 0.25, 0.5 and 1. The model results for avaergar Nusselt number evaluation was in good agreement with other published work for similar configuration. The results show that convective average Nusselt number decreases by 93% when the inclination angle increased from 0° to 90°due to the trapped vortices that limit the airflow throughout the cavity. The air flowing through the cavit is maximum when the the inclination angle is zero even at higher values of Raylight number. Results show also that decreasing the opening ratio from 1 to 0.25 leads to a drop in heat loss by 22.79%. A simple correlation has been developed for calculating the the average Nusselt number as a function of Rayleigh number, opening ratio and inclination angle.Item Numerical Study of the Turbulent Air Flow through the Turbocharger Compressor Using Different Rotor Shapes(2021) Abdelmadjid ChehhatThe turbulent air flow through the turbocharger is studied, considering the full stage of the centrifugal compressor, consisting of an air inlet, leading to an impeller that discharges the air radially through a vaneless diffuser in the volute. The objective of this study is the prediction of the influence of impeller blades geometry on the flow local characteristics (velocity and pressure) and on the local characteristics of turbulence represented by the standard k- ε model, for this, three types of impellers that have the same size and the same number of blades are considered, they differ only in inlet and exit blade angle. All simulations are carried out for the same rotational speed of 100000 rpm, and several points of the operating range, it is chosen for representing the results one of these points at flow rate of 0.47 kg/s, the velocity fields is presented in the axial plane, and transverse plan, whereas for the turbulence intensity we show the diffuser with each type of impeller to give an idea about the distribution of turbulence intensity in the diffuser. It is found from the computational fluid dynamics analysis that the rotor design presents a considerable effect not only on the fluid flow field and turbulence characteristics, but also on the performances and operating range of the turbocharger compressorItem Simulation numérique de la convection naturelle laminaire dans une conduite verticale(2007-08-29) Abdelmadjid ChehhatDans ce travail, nous présentons une étude numérique du phénomène de la convection naturelle laminaire dans une conduite verticale, dont la paroi est maintenue à une température constante. Les équations régissant ce phénomène, ont été résolues par une approche numérique basée sur la méthode des volumes finis. Nous avons représenté les champs de vitesses, de températures, et de pressions, ainsi que la variation du nombre de Nusselt moyen en fonction du nombre de Rayleigh. Les simulations numériques ont été faites en considérant des valeurs du nombre de Rayleigh qui varient entre 1 et 105, et cela pour des rapports d’aspect égalent 3, 5, 8 et 12. Les résultats obtenus sont comparés à ceux de la littérature et un bon accord a été trouvé.