No abstract

A mixed convective heat transfer in hollow perforated pin fins array with inline arrangement subject to a vertical impinging flow is numerically investigated. The governing equations based on Navier-Stockes equations are solved by adopting a three dimensional finite volume numerical model. The aim is to asses the thermal performance of the new heat sink (perforated pin fins) under several significant parameters such geometrical position of the hole (ht =10, 20, 30, 40mm) and the Reynolds number (Re = 50-500). The effects of the height of horizontal hole and the vertical perforation on the thermal dissipation rate and the pressure drop are explicetly undertaken and compared to the standard configuration (without perforation).

In this work, a numerical study of a laminar mixed convection in a inclined thick duct is considered. A uniform heat flux is applied over the entire circumference of the tube. The governing differential equations were solved by a finite volume method. The SIMPLE algorithm for pressure-velocity coupling was adopted. A parametric study is carried out to analyze the effect of the Grashof number, the angle of the duct inclination and the wall conductivity on the thermal-fluid fields. Several numbers of Grashof (4. 104, 4. 106, 4. 107) are considered for an angle of inclination equal: 0°, 30° and 60°. For material of the wall, we chose Report/ratio of conductivity (K=kp/kf) of the copper (K=19000), iron (K=3600) and aluminium (K=11500). The results are analyzed by examining the velocity, pressure and temperature fields §. The axial evolution of the Nusselt number and that of the parietal constraints are examined for various studied cases.

The aim of this study is to examine by means of three-dimensional numerical simulations the thermal-fluid features in elliptical pin fin heat sink. The passive heat transfer enhancement technique is used to comprehend and control the cooling process. This passive methodology is based on pin fins arrangement, hydrodynamic and geometrical parameters. The present numerical results are confronted with experimental measurements in open literature which used one-dimensional model to explore the thermal field. A good agreement was found especially around the optimal fins dimensions. A parametric study has been carried out to deeply analyse the three-dimensional thermal-fluid fields of the heat sink for various key parameters range such the Reynolds number (Re = 50–250) and the aspect ratio (γ=H/d=5.1-9.18). Some new observations and results are obtained thanks to numerical simulations as tool of investigation. It is shown that the fins circumferential temperature is almost uniform. Furthermore, a better cooling is obtained when the Reynolds number increases mainly when the inlet velocity u0> 0.3m/s. The most suitable value of the aspect ratio is attained for γ=8.16, which ensure an optimal cooling process of the pins. A new global Nusselt number correlation was developed for engineering applications.

The technological progress made in recent years has driven electronic apparatus to become not only more efficient and work faster but also considerably smaller in weight and size. Furthermore, the power densities of these devices have known an impressive increase. However, the challenge for the electronic industry is the lifetime device improvement by controlling the adequate removal of their excess heat. The use of more efficient cooling systems is, therefore, crucial in order to ensure durable device functionality. In this work, computational simulation was carried out to study the enhancement cooling process mixed convection of an electronic component (CPU mounted in a motherboard) using a new design of a heat exchanger by combining the heat sink (the finned surface) and the fan in a single component, this allows more heat to be moved faster and with less energy than a conventional cooler. Three radial heat sinks (HS18, HS24 and HS36) are considered depending on circumferential fin numbers ( n  =  18, 24 and 36). The effect of Reynolds number, heat flux and rotational velocity is investigated, and the optimum comprehensive performance was determined. The results reveal the cooling performance turns out to be better for heat sink with n  =  36. The rotational velocity operates a significant effect on the temperature field only for values below than 900 rpm. We also found that the improvement in the Nusselt number and its percentage enhancement is intensified with increased rotational velocity and decreased with heat flux. A bigger Ω and ReΩ meant a more obvious heat transfer enhancement (NuΩ/Nu0) in the case of smaller Q, but (NuΩ/Nu0) decreased with increasing Q.