Ahmed Bettahar

Bio: Ahmed Bettahar is an academic researcher. The author has contributed to research in topics: Thermal energy & Airflow. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Experimental study of aero-thermal heat sink performances subjected to impinging air flow

Abstract: Received: 20 July 2018 Accepted: 24 December 2018 In this study, experimental investigation of thermal and aerodynamic performances of a rectangular mini-channel heat sink subjected to an impinging air jet was carried out with the aim to improve the cooling performance of personal computer CPUs. The influence of the impinging distance on the velocity profile, the pressure drop, the case temperature, the thermal resistance, and the heat transfer coefficient are studied. Moreover, the effect of the positioning of the microprocessor (heat source) on the thermal performance was investigated. The results show a ratio \"height jet/diameter\" Y/D=0.606 offer a better cooling, and a longitudinal displacement of the heat source (central processor unit) 10 mm from the original position (center) improve the cooling performance. The enhancement rate was in a range of 10% compared to the initial position (central position before shifting the source).

Heat transfer improvement study of electronic component surfaces using air jet impingement

Abstract: Impinging jet is a method for attaining high convective heat transfer coefficients and so increasing the heat transfer from cooling surfaces. In this work, improvement in the heat transfer from copper plate patterned surfaces having high heat flux depending on developing technologies in order to solve increased thermal load problem of the electronic equipments such as microchips are numerically examined by using an impingement jet technique. Five different patterned surfaces as reverse and straight circles are placed inside rectangular channels consisting of one open and three blocked sides. Governing 3D Navier–Stokes and energy equations as steady are solved by using Ansys Fluent software program with k-e turbulence model. Air used as jet fluid has 300-K inlet temperature. A constant heat flux of 1000 W/m2 is implemented to the patterned surfaces while top and side surfaces are adiabatic. The study is conformed for different Re numbers ranging from 4000 to 10000 and different jet-to-plate distances (H/Dh) from 4 to 12 for two different surface configurations. The numerical results are agreed well with numerical and experimental studies existed in the literature. The results are presented as mean Nu numbers and surface temperature variations for each of the analyzed patterned surfaces. The velocity and temperature contours and jet flow streamline distributions are assessed for different Re numbers and H/Dh ratios. For Re = 10000 and H/Dh = 12, the mean Nu number value on the straight-circle-patterned surfaces is 24.13% higher than that of the reverse-circle-patterned.

Design and Experimental Evaluation of Innovative Wire-to-Plane Fins’ Configuration for Atmosphere Corona-Discharge Cooling Devices

Abstract: Electro-fluid-dynamic cooling devices (EFAs) are being recognized due to their enormous advantages for their application in several industrial sectors, their performance benefits from generated ionic winds and their singular features, which make them competitive with conventional fans and heatsinks. Due to the problems in the electronics industry, where traditional refrigeration systems are not effective due to their dimensions, this study analyzes an innovative arrangement based on wire-to-plane fins by direct current (DC) positive corona discharge in atmospheric air for applications. The paper focuses on optimizing the multicriteria geometry of the electrodes. Several parameters are analyzed such as the gap between emitter and ground electrodes, the electrode materials and geometry, the diameter of the high-voltage electrode and the influence of the dielectric barriers located near the corona electrode to improve heat exchange. Experimental validation shows the potential of this arrangement related to weight, volume, non-mobile parts and silence.

Spatio-Temporal Changes in the Turbulent Kinetic Energy of a Rectangular Jet Impinging on a Slotted Plate Analyzed with High Speed 3D Tomographic-Particle Image Velocimetry

Abstract: Received: 11 December 2018 Accepted: 25 November 2019 The purpose of this study is to investigate the temporal changes of the Turbulent Kinetic Energy (TKE) of an impinging rectangular self-excited jet in order to identify a reduced zone that is active in producing TKE. An experimental set up consisting of a rectangular jet impinging on a slotted plate was considered for a Reynolds Number Re=5435. This configuration is accompanied by a high level of noise due to the appearance of self-sustained tones that occur in optimal conditions for energy transfer between fluctuating velocity and acoustic field. High Speed Tomographic Particle Image Velocimetry (PIV) technic was used to evaluate the Turbulent Kinetic Energy (TKE) field derived from the aerodynamic one. Through this study, it was found that a reduced volume of height of 0.5*H and a length of 2*H (where H is the height of the nozzle exit) was satisfactory to represent the three-dimensional TKE activity between the jet exit and the plate. The findings of this research lies in investigating the evolution of the TKE that could feed the acoustic generation in order to develop new techniques of noise control. Such sub-volume of the flow would also save a considerable time of calculation.

An Analytical Study of the Optimized Performance of an Impingement Heat Sink

Abstract: The results of a study of a new and unique high performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross-flow. The effects of the fin thickness and gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel-gaps of 0.8 mm with appropriate central cut-out yielded heat transfer coefficients over 1500 W/m2 K at a pressure drop of less than 100 N/m2 , as is typically available in high-end workstations. A detailed study of flow-through heat sinks, subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.Copyright © 2003 by ASME