liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Numerical investigation of the turbulent flow and heat transfer around a heated cube cooled by and impinging jet in a cross-flow
Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Impinging jets are used for many industrial applications where high heat and mass transfer rates are required. The electronic industry is one of the fastest growing industries and applications of cooling technology in this field are of considerable importance. Forced channel flow is frequently used as a cooling technique. In combating the whole thermal load with forced channel flow, excessive flow rates will be required. The typical electronic system contains one or a few high heat–dissipating components. One possible method to face this problem is to divide the channel flow into an impinging jet and a low-velocity cross-flow. The impinging jet is placed over the high heat-dissipating component and provides a local region with high cooling performance, especially at the stagnation point. The cross-flow is important to insure that well-distributed cooling performance is provided at the remaining part of the electronic system, which requires less cooling.

Impinging jets are also of great scientific interest. Extensive experimental and numerical research has been carried out to predict the flow and heat transfer characteristics in the stagnation region of an impinging jet where most of the investigations have been focused on axi–symmetric round impinging jets without any cross-flow.

The purpose of this study is to examine a spot cooling technique consisting of en impinging jet in combination with a low-velocity cross-flow by use of CFD. The cases are limited to a heated wall-mounted cube with different height which is placed in a channel with different heights and cooled by an impinging jet and a cross-flow with different velocities. The study can be divided into three parts: a verification study, a detailed study and a parametric study.

The verification part consists of a verification of two steady-state Reynolds-Averaged Navier-Stokes turbulence models, a v2-f model and a Reynolds Stress Model (RSM). The results show that both models predicted similar results in the near-wall region except in the stagnation region from the impinging jet where the wall-normal turbulent Reynolds stresses and the turbulent kinetic energy where significantly higher in the RSM than in the v2-f model and in the measurements. The general trend was that the predicted surface temperature and the mean velocity field in the free shear-flow, i.e. far from the walls, from the RSM was in better agreement with the measurements than the results from the v2-f model.

The detailed study presents an unsteady simulation by use of Large Eddy Simulation (LES) for a case identical to the verification study in order to predict the time-averaged velocity field, the turbulence characteristics and the heat transfer rate. The agreements between the results from the LES and the measurements were in general improved compared with the RSM and the v2-f model especially in the stagnation region from the impinging jet.

The parametric study is carried out by use of the validated RSM where influence of the velocities of the impinging jet and the cross-flow, the distance between the top and bottom plates, and the height of the cube on the heat transfer rate and on the pressure drops was investigated.

Place, publisher, year, edition, pages
Linköping: LiU-tryck , 2009. , 84 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1227
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-52265ISBN: 978-91-7393-740-5 (print)OAI: oai:DiVA.org:liu-52265DiVA: diva2:280980
Public defence
2008-12-12, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2009-12-14 Created: 2009-12-14 Last updated: 2012-11-14Bibliographically approved
List of papers
1. Investigation of flow and heat transfer of an impinging jet in a cross-flow for cooling of a heated cube
Open this publication in new window or tab >>Investigation of flow and heat transfer of an impinging jet in a cross-flow for cooling of a heated cube
2006 (English)In: Journal of Electronic Packaging, ISSN 1043-7398, E-ISSN 1528-9044, Vol. 128, no 2, 150-156 p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46016 (URN)10.1115/1.2188948 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
2. RSM and v² − f study on the flow behaviour of an impinging jet in a cross-flow on a wall-mounted cube
Open this publication in new window or tab >>RSM and v² − f study on the flow behaviour of an impinging jet in a cross-flow on a wall-mounted cube
2007 (English)In: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 7, no 6, 311-322 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
electronic cooling, impinging jets, CFD, RSM, PIV, particle image velocimetry, computational fluid dynamics, cross-flow, wall-mounted cubes, turbulence modelling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48007 (URN)10.1504/PCFD.2007.014681 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
3. RSM predictions of an impinging jet in a cross flow on a heated wall-mounted cube
Open this publication in new window or tab >>RSM predictions of an impinging jet in a cross flow on a heated wall-mounted cube
2006 (English)In: Proceedings at 13th International Heat Transfer Conference, 2006Conference paper, Published paper (Refereed)
Abstract [en]

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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-41707 (URN)58792 (Local ID)58792 (Archive number)58792 (OAI)
Conference
13th International Heat Transfer Conference, Sydney, Australia, 13-18 August, 2006
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2012-11-14
4. Large-eddy simulation of an impinging jet in a cross-flow on a heated wall-mounted cube
Open this publication in new window or tab >>Large-eddy simulation of an impinging jet in a cross-flow on a heated wall-mounted cube
2009 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, Vol. 52, no 3-4, 921-931 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2009
Keyword
Large-eddy simulation, Impinging jet in a cross-now, Reynolds stress model, Electronic cooling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-16620 (URN)10.1016/j.ijheatmasstransfer.2008.03.035 (DOI)000262556200043 ()
Available from: 2009-02-07 Created: 2009-02-06 Last updated: 2014-03-18Bibliographically approved
5. Investigation of heat transfer and pressure drop of an impinging jet in a cross-flow for cooling of a heated cube
Open this publication in new window or tab >>Investigation of heat transfer and pressure drop of an impinging jet in a cross-flow for cooling of a heated cube
2008 (English)In: Journal of heat transfer, ISSN 0022-1481, E-ISSN 1528-8943, Vol. 130, no 12, 121401-121413 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
ASME International, 2008
Keyword
electronics cooling, impinging jet, CFD, RSM
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-16851 (URN)10.1115/1.2969266 (DOI)000262842200004 ()
Available from: 2009-02-21 Created: 2009-02-20 Last updated: 2017-12-13Bibliographically approved

Open Access in DiVA

No full text

By organisation
Energy SystemsThe Institute of Technology
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 557 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf