Thecurrent trends toward the greater functionality of electronic devices areresulting in a steady increase in the amount of heatdissipated from electronic components. Forced channel flow is frequently usedto remove heat at the walls of the channel wherea PCB with a few high heat dissipating components islocated. The overall cooling strategy thus must not only matchthe overall power dissipation load, but also address the requirementsof the "hot" components. In order to cool the thermalload with forced channel flow, excessive flow rates will berequired. The objective of this study is to investigate iftargeted cooling systems, i.e., an impinging jet in combination witha low velocity channel flow, can improve the thermal performanceof the system. The steady-state three-dimensional (3-D) model is developedwith the Reynolds-Stress-Model (RSM) as a turbulence model. The geometricalcase is a channel with a heated cube in themiddle of the base plate and two inlets, one horizontalchannel flow, and one vertical impinging jet. The numerical modelis validated against experimental data obtained from three well-known cases,two cases with an impinging jet on a flat heatedplate, and one case with a heated cube in asingle channel flow. The effects of the jet Re andjet to-cross-flow velocity ratio are investigated. The airflow pattern aroundthe cube and the surface temperature of the cube aswell as the mean values and local distributions of theheat transfer coefficient are presented.

The current trends of electronic devices are resulting in a steady increase in the dissipated heat from the components. One possible cooling method is to use an impinging jet and a low-velocity channel flow. The objective is to investigate the performance of the ^‾v² − f model and RSM in order to predict the time-average velocity and the Reynolds stresses. The case is a channel with a cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet above the cube. The turbulence models are validated against earlier PIV measurement with identical set-up.

The objective of this study is to investigate the performance of a Reynolds Stress Model (RSM) with a two-layer model in the near-wall region in order to predict the mean velocity field, the turbulence characteristics and the heat transfer rate. The numerical predictions are validated against detailed measurements for the turbulent flow features and the surface temperatures with identical set-up.

The experimental set-up consists of an array of five wall-mounted cubes and only the third cube is heated. The cube is cooled by a low-velocity chaunel flow and an impinging jet from a circular nozzle above the third cube.

The time-averaged velocity field and the Reynolds stresses near the third cube were measured by PIV. The time-averaged surface temperature on the third cube was measured by a low-wavelength infrared imaging system. The measurement part of the present study was carried out at the Department of Applied Physics, Delft University of Technology, Delft, the Netherlands.

The linear pressure-strain model proposed by Launder and Shima (1989) is used in the RSM. The turbulent heat fluxes are modelled by the eddy-diffusivity hypothesis in analogy with the eddyviscosity hypothesis used for Reynolds stresses with a constant value of the turbulent Prandtl number. The mesh was refined enough near the solid walls (y⁺ ≈1) to solve all boundary layers. The commercial finite-volume code Fluent 6.1.22 was used.

A comparison between the results from the CFD predictions and the measurements shows a good agreement of this the complex flow field. The results revealed that there are several flow-related phenomena that affect cooling performance, such as stagnation points, separations, curvature effects and re-circulating wake flows.

A large-eddy simulation (LES) is performed in order to predict the mean velocity field, the turbulence characteristics and the heat transfer rate of an impinging jet in cross-flow configuration on a heated wall-mounted cube. The WALE model was used to model the subgrid-scale tensor. The results from the LES are compared with a Reynolds stress model (RSM) and against earlier measurements with identical set-up. A comparison between the results from the predictions and the measurements shows that in general the LES has better agreement with the measurements compared to the RSM and particularly in the stagnation region of the impinging jet.

The objective of this study is to investigate the thermal performance and the cost measured in pressure drops of a targeted cooling system with use of an impinging jet in combination with a low-velocity channel flow on a heated wall-mounted cube. The effects of the Reynolds numbers of the impinging jet and the cross-flow, as well as the distance between the top and bottom plates, are investigated. A steady-state 3D computational fluid dynamics model was developed with use of a Reynolds stress model as turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet. The numerical model was validated against experimental data with a similar geometrical setup. The velocity field was measured by particle image velocimetry and the surface temperature was measured by an infrared imaging system. This case results in a very complex flow structure where several flow-related phenomena influence the heat transfer rate and the pressure drops. The average heat transfer coefficients on each side of the cube and the pressure loss coefficients are presented; correlations for the average heat transfer coefficient on the cube and the pressure loss coefficients are created.