Influence of types of nanoparticles, nanoparticles volume concentration and types of cooler metals on the heat transfer in a mini-channel cooler

In the present work, we have studied the effect of three different types of nanoparticles, nanoparticles volume concentration and types of cooler metals on heat transfer in a mini channel cooler numerically. In these simulations, we have considered the Cu-H2O, the Ag-H2O and the Diamond-H2O with different volume fractions in the range of 0,02%-0,1% and for two types of cooler materials for cooling an electronic component. In these conditions, the inlet velocity is constant for the three different types of nano-fluids. The power of the electronic component is equal to 130 W. The numerical results are developed for a Reynolds number equal to 1414 and a steady-state. The simulation was performed using commercial software, ANSYS-Fluent 15.0. The obtained results show that the average heat transfer coefficient increases with the increase of the volume fraction of the nanoparticles (Cu, Ag, Diamond) and with the decrease of the temperature of the electronic component. In these conditions, the average heat transfer coefficient is the highest for the H2O–diamond nanofluid compared with the other nanofluids the Cu-H2O and the Ag-H2O. Furthermore, the types of cooler metals have considerable effects on the amelioration of the temperature of the electronic components

Three-dimensional numerical study of thermal exchanges in different geometry sections of mini-channels using three different nanoparticles

In the present work, we have studied the thermal exchanges of different geometry sections of mini-channels of a cooler numerically. Particularly, we have chosen a mini channels cooler copper for cooling an electronic chip IGBT. In our simulation of three-dimensional (3D), we have compared the numerical results for the different forms of the proposed mini-channels and the three different types of nano-fluids by using the Cu-water, the Ag-water, and the Diamond-water with a volume fraction of 0.02%. The numerical results are obtained by choosing a Reynolds number (Re) between 100 and 900 and considering that the flow regime is stationary. The simulation was performed using commercial software, ANSYS-Fluent 15.0. The results obtained show that the increase of the exchange surface between the walls of the mini channels and the cooling fluid makes increases the heat exchange coefficient and the improvement of the maximum junction temperature of the electronic chip IGBT with the increase of the Reynolds number. The choice of nanoparticles has considerable effects on improving the heat transfer and the maximum junction temperature of the chip IGBT

A viscoelastic-viscoplastic model for a thermoplastic and sensitivity of its rheological parameters to the strain-rate

The behavior of thermoplastics depends on several factors, mainly time and temperature. The present work is the subject of an analysis of the dependence of viscoelastic viscoplastic parameters of a model of rheological behavior at the time. The material considered in this study is a polyamide 6. The model of applied behavior is represented by the Kelvin-Voigt viscoelastic mechanism mounted in series with a viscoplastic branch of Bingham. Following a mathematical formulation of the equations governing the model, tensile tests at different strain rates are conducted. The model parameters are then identified by inverse analysis. The technique of genetic algorithms has been favored. A nonlinear dependence of these parameters on the rate of strain has been observed. The dependence function has been established by a nonlinear regression technique. The comparison of the experimental results with those obtained by the model reveals a satisfactory agreement, hence the validation of the approach adopted

On the use of the stepped isostress method in the prediction of creep behavior of polyamide 6

The stepped isostress method (SSM) is an advanced technique which allows the prediction of the long-term behavior and enables the construction of creep master curves of materials with short-term experimental tests. However, the performance of this method is highly dependent on the numerical model and the time spent in data processing. In this paper, the effect of the extrapolation techniques on the creep curves trend is investigated using the SSM data of Polyamide test. Three extrapolation functions are used to offset the delay of the stress history: polynomial, power and exponential functions. Furthermore, a numerical routine is developed during the last step of the SSM, where the shift factors are computed taking into account the rescaling and the dwell times of each level of stresses. The processing of the SSM raw data has revealed that the rescaling parameters are the most determining factors to reach an accurate long-term creep curves. The rescaling process has shown an appropriate time, whether achieved by the exponential or power functions. Larger shift factors for exponential functions are assessed and therefore a long period of creep master curve was obtained

Effect of the position of parallelogram ribs in micro channel on heat transfer using diamond nanoparticles

In the present work, we have studied numerically three dimensions, the impact of the position of parallelogram ribs in a micro-channel on thermal exchange. In this study, we proposed three cases of micro-channel heat sinks with parallelogram ribs. As well as one case without ribs, in each of the three cases, we varied the parallelogram rib positions on the micro-channel. The main purpose of this study is to find the best position for parallelograms ribs in which the heat dissipation is useful for improving the thermal performance of the micro-channel as well as improving the cooling of electronic components. We have chosen silicon micro-channel drains for four cases. Constant heat flux is applied to the bottom surfaces and using a nanofluid diamond-water with 5% volume concentration of diamond nanoparticle as a coolant. The simulation has been carried out using the commercial software ANSYS-Fluent. Reynolds number (Re) has been taken between 200 and 400 with the corresponding inlet velocity from 1.53 m/s to 3.01 m/s, and the flow regime has been assumed to be stationary. The numerical results show that the parallelogram ribs position of the micro-channel in the second case gave an improvement in heat exchange, where the Nusselt number is higher than in the other cases, and showed a reduction in the temperature of the heated bottom wall compared to the other cases. Also, the micro-channel shape in the second case can be used to cool the electronic components. The results also showed that with increasing Reynolds number (Re), the friction factor of the micro-channel decreases in all cases. At the same time, we find the lowest value of the thermal resistance in the second case and the biggest value in the first case, base micro-channel without ribs

INFLUENCE DE L’HUMIDITE SUR LES CARACTERISTIQUES MECANIQUES DES POLYMERES THERMOPLASTIQUES

Les matériaux polyamides ont des caractéristiques mécaniques modérées à l’état initial. L’utilisation de ces matériaux est étroitement liée à une meilleure connaissance de leur comportement en service face au vieillissement hygrothermique en particulier. La sensibilité à l’humidité est considérée comme étant une cause majeure de la chute des propriétés mécaniques.La démarche de ce travail consiste à une étude expérimentale sur l’influence de l’humidité sur les caractéristiques mécaniques

CONTIBUTION DANS L’EXPOLRATION DES PHENOM7NES VISCOELASTIQUE DES COMPOSITES THERMOPLASTIQUE

De par leur nature les polymères, ont la particularité d’avoir un caractère viscoélastique très prononcé dans leurs comportements mécaniques même à température ambiante. Ceci est tributaire à leurs températures de fusion qui sont relativement basses en comparaison aux métaux et céramique. Ce caractère viscoélastique se manifeste suite à des sollicitations dynamiques ou statiques. Ce travail investigue le comportement en fluage de polymère. En effet, sous une sollicitation constante un polymère continue à se déformer au cours du temps, et pour des périodes très longues ces déformations peuvent dépasser les limites de conception autorisées ou même aboutir à une rupture sous des contraintes bien en dessous de la contrainte ultime du matériau. Une prédiction du comportement en fluage de ces matériaux à très long terme est donc plus que nécessaire. Le problème auquel se confronte cette prédiction est la non disponibilité d’approches théoriques. Pour cette raison, actuellement les approches empiriques sont adoptées. Ces dernières nécessitent du temps d’essai extrêmement long ou carrément impraticable. L’issue de cette problématique réside dans des techniques de superpositions temps-température ou temps-contrainte. Le fondement d’une très récente variante de ces techniques a été proposée qui est appelée SSM ; la méthode de contraintes étagées. La contribution importante de cette recherche consiste au raffinement et à la validation de cette techniqu

Experimental determination of elastic modulus of elasticity and Poisson’s coefficient of date palm tree fiber

The present study is an attempt to valorize local vegetable fibers by evaluating thire effectiveness as a new composite biomaterial. Our aim was to determine the mechanical characteristics, namely the elastic modulus and Poisson’s coefficient, of a fiber, locally called “Lif,” that is a natural material extracted from different date palm tree varieties in Biskra, a region situated in southeastern Algeria. This study compares the mechanical characteristcs of the Lif date palm tree fiber with other synthetic and plant fibers studied previously

Caractérisation physique et mécanique du bois et des fibres issus d’une palme mûre de palmier dattier

La disponibilité en quantité importante des sous-produits renouvelable des palmiers dattiers laisse envisager leur utilisation comme renfort dans les matériaux composites et les structures d’isolation. Ceci nécessite la caractérisation physico-mécanique des différentes composantes du palmier. Dans ce contexte, cette étude a été entamée pour la caractérisation d’une composante importante du palmier qui est la palme mûre. La palme étant décomposée essentiellement en deux parties, le Pétiole et le Rachis, la caractérisation a été portée alors sur le bois fibreux et les fibres de ces deux parties. La caractérisation physique concernera la masse volumique des fibres et de la matrice végétale (lignine) ainsi que le taux d’humidité dans les différentes parties de la palme. Les essais mécaniques ont permis de déterminer les caractéristiques mécaniques du bois fibreux et des fibres extraites des deux parties de la palme après le séchage. À l’issue de cette étude, les résultats obtenus montrent l’influence de la position de l’échantillon testé sur les propriétés physico-mécaniques. Ils ont permis également de situer ce type de bois fibreux et ces fibres parmi d’autres résultats de la littérature scientifique et d’envisager de les utiliser dans la mise en œuvre des matériaux composites et dans des éléments d’isolation