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Experimental and numerical study of the thermal and hydraulic effect of EMC screens in radio base stations: detailed and compact models
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Today’s telecommunication cabinets use Electro Magnetic Compliance (EMC) screens in order to reduce electromagnetic noise that can cause some miss functions in electronic equipment.

Many radio base stations (RBSs) use a 90-degree building architecture: the flow inlet is perpendicular to the EMC screen, which creates a complex flow, with a 90-degree air turn, expansions, compressions, perforated plates and PCBs. It is of great interest to study how the EMC screen interacts with the rest of components and analyze the total pressure drop and how much the flow pattern changes due to the placement of the screen.

Velocity, pressure and temperature measurements as well as flow pattern visualizations have been carried out to gain good insight into the flow and heat transfer characteristics in a subrack model of an RBS. Furthermore, these measurements have been very useful for validating detailed CFD models and evaluating several turbulence models.

Nowadays, industrial competition has caused a substantial decrease in the time-to-market of products. This fact makes the use of compact models in the first stages of the design process of vital importance. Accurate and fast compact models can to a great extent decrease the time for design, and thus for production.

Hence, to determine the correlations between the pressure drop and flow pattern on the PCBs as a function of the geometry and the Reynolds number, based on a detailed CFD parametric study, was one objective. Furthermore, the development of a compact model using a porous media approach (using two directional-loss coefficients) has been accomplished. Two correlations of these directional loss coefficients were found as a function of the geometry and Reynolds number.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006.
Series
Trita-REFR, ISSN 1102-0245 ; 06/57
Keyword [en]
sub-rack, perforated plate, air cooling, 90 degrees turn, flow deistribution, CFD, measurement
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4265ISBN: 978-91-7178-553-4 (print)OAI: oai:DiVA.org:kth-4265DiVA: diva2:11531
Public defence
2007-01-29, Salongen, KTHB, Osquars Backe 31, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100630Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2012-03-23Bibliographically approved
List of papers
1. Modelling of EMC screens for radio base stations Part 1: Experimental parametric study
Open this publication in new window or tab >>Modelling of EMC screens for radio base stations Part 1: Experimental parametric study
2004 (English)In: ITherm 2004, Vol 1, IEEE , 2004, 463-470 p.Conference paper, Published paper (Refereed)
Abstract [en]

Enclosing electronics in sealed metal boxes provides good electromagnetic shielding, but evidently restricts the air movement necessary for adequate cooling. In order to meet ElectroMagnetic Compatibility (EMC) requirements, a perforated plate (an EMC screen) must be used. The design of this screen must provide a sufficient free area ratio for the adequate airflow, but at the same time the holes must be small enough to block electromagnetic radiation. An experimental set-up that represents a Radio Base Station (RBS) subrack was built inside a wind tunnel. The airflow pattern and pressure drop through the EMC screen were investigated experimentally for different subrack geometries, screen porosities and velocities, and the recirculation zones were identified. The study was performed by means of pressure and velocity measurements, together with smoke visualization under isothermal conditions.

Place, publisher, year, edition, pages
IEEE, 2004
Keyword
EMC, Hot wire anemometer, Inclined flow, Perforated plate, Pressure drop, Pressure measurement, Smoke visualization, Subrack
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-6731 (URN)000222478500065 ()2-s2.0-4444297390 (Scopus ID)0-7803-8357-5 (ISBN)
Conference
ITherm 2004 - Ninth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems; Las Vegas, NV; United States; 1 June 2004 through 4 June 2004
Note

QC 20100629

Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2014-12-09Bibliographically approved
2. Smoke and CFD visualization of the flow after an EMC screen in a sub-rack model
Open this publication in new window or tab >>Smoke and CFD visualization of the flow after an EMC screen in a sub-rack model
2005 (English)In: Proceeding of the THERMINIC 05, 2005Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-6732 (URN)
Note
QC 20100629Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2012-01-23Bibliographically approved
3. Modelling of EMC Screens for Radio Base Stations: Part 2: Evaluation of Turbulence Models
Open this publication in new window or tab >>Modelling of EMC Screens for Radio Base Stations: Part 2: Evaluation of Turbulence Models
2004 (English)In: Proc. 9th  InterSociety Conf. on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm 2004), Las Vegas, NV, USA, IEEE Press, 2004, 471-478 p.Conference paper, Published paper (Refereed)
Abstract [en]

The objective of this paper is to investigate the performance of five well-known turbulence models and 2 wall treatments, in order to predict the details of the flow patterns through an EMC (ElectroMagnetic Compatibility) screen. The employed turbulence models are investigated in the present study is four different eddy-viscosity models; the standard k-ε model, the renormalization group (RNG) k-ε model, the realizable k-ε model and the k-ω model, as well as the Reynolds stress model, RSM. The commercial finite volume code Fluent 6.1 was used for simulation.

A steady-state three-dimensional model, which serves as the most accurate representation of the model, was used in order to predict the details of the air flow paths and pressure field. The flow was assumed to be isothermal, turbulent and incompressible.

The numerical predictions were validated experimentally by using wind tunnel measurements and smoke visualization. The performances of the turbulence models are discussed and the RSM results are compared with other two-equation turbulence models. The result shows that choosing the right turbulence model and wall treatment does not have a great influence on the prediction of pressure drop and the velocity field. The pressure field is over predicted about 15% and the velocity average deviation at several locations before and after the screen is less than 10%. Simulations using a hydraulic impedance surface, i.e. without a detail modeling of the EMC screen, show that the pressure field is also over predicted and great differences are observed in the velocity field.

Place, publisher, year, edition, pages
IEEE Press, 2004
Keyword
RNG, RSM, k-ε, k-ω, pressure drop, perforated plate, porosity, EMC screen, subrack, velocity profile, flow pattern, hydraulic impedance
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-63407 (URN)2-s2.0-4444325242 (Scopus ID)0-7803-8357-5 (ISBN)
Conference
9th InterSociety Conf. on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm 2004), Las Vegas, NV, USA
Note
QC 20120131Available from: 2012-01-23 Created: 2012-01-23 Last updated: 2012-01-31Bibliographically approved
4. Detailed CFD modelling of EMC screen for radio base stations: a benchmark study
Open this publication in new window or tab >>Detailed CFD modelling of EMC screen for radio base stations: a benchmark study
2007 (English)In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 30, no 4, 754-763 p.Article in journal (Refereed) Published
Abstract [en]

The objective of this paper is to investigate the performance of five well-known turbulence models, in order to find a model that predicts the details of the flow patterns through an electromagnetic compatibility (EMC) screen. The turbulence models investigated in the present study are five different eddy-viscosity models; the standard k-ε model, the renormalization group (RNG) k-ε model, the realizable k-ε model, the standard k-ω model, as well as the shear stress transport k-ω model. A steady-state 3-D detailed model, which serves as the most accurate representation of the model, was used in order to evaluate the details of the airflow paths and pressure field. The flow was assumed to be isothermal, turbulent and incompressible. A general model that covers a considerable range of velocities and geometries was validated experimentally by wind tunnel measurements. The result shows that for most of the k-ε models used with correct y+ and mesh strategy, the pressure drop and the velocity field deviation is small compared to experimental data. The k-ω models overpredict the overall pressure drop. When using the RNG k-ε model, the total static pressure drop predicted differs around 5%-10% and the average velocity deviation at several locations before and after the screen is around 5%.

Keyword
Electromagnetic compatibility, Electromagnetic compatibility (EMC) screen, Flow control, Flow pattern, Hot wire anemometer, Inclined flow, kε, k-ω, Perforated plate, Porosity, Porous materials, Pressure drop, Renormalization group (RNG), Subrack
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-6734 (URN)10.1109/TCAPT.2007.910048 (DOI)000251431100028 ()2-s2.0-36948999874 (Scopus ID)
Note
QC 20100630. Uppdaterad från Accepted till Published (20100908)Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2017-12-14Bibliographically approved
5. Detailed CFD Modelling of EMC Screen for Radio Base Stations: A Conjugate Heat Transfer Problem
Open this publication in new window or tab >>Detailed CFD Modelling of EMC Screen for Radio Base Stations: A Conjugate Heat Transfer Problem
2007 (English)In: International Journal of Heat Exchangers, ISSN 1524-5608, Vol. 8, no 1, 95-116 p.Article in journal (Refereed) Published
Abstract [en]

The objective of this paper is to perform an experimental as well as CFD investigations of the conjugate heat transfer problem in a sub-rack slot model. A steady-state three-dimensional detailed model, which serves as the most accurate representation of the model, was used in order to evaluate the details of the airflow paths and temperature field.

A general model that covers a considerable range of velocities, screen porosities and heat fluxes was validated experimentally by wind tunnel measurements. The result shows that the RNG k-ε model used with correct y+ and mesh strategy accurately predicts the temperature field. The average temperature deviation at several locations is less than 4% compared to experimental data. The influence of the velocity, screen porosity, heat flux and presence of the EMC screen on the PCB temperature field is commented.

Place, publisher, year, edition, pages
R.T Edwards Inc., 2007
Keyword
RNG, k-ε, porosity, EMC screen, sub-rack, heat transfer
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-63290 (URN)2-s2.0-34547290987 (Scopus ID)
Funder
StandUp
Note
QC 20120131Available from: 2012-01-23 Created: 2012-01-23 Last updated: 2012-03-23Bibliographically approved
6. Detailed CFD modelling of EMC screen for radio base stations: a parametric study
Open this publication in new window or tab >>Detailed CFD modelling of EMC screen for radio base stations: a parametric study
2009 (English)In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 32, no 1, 145-155 p.Article in journal (Refereed) Published
Abstract [en]

The objective of this paper is to make a parametric study of the hydraulic resistance and flow pattern of the flow after an electromagnetic compatibility screen and between two printed circuit boards (PCBs) in a model of a 90° subrack cooling architecture. The parametric study is carried out using a detailed 3-D model of a PCB slot. The detailed model was experimentally validated in a previous paper by the authors. Seven parameters were investigated: velocity, inlet height, screen porosity, PCB thickness, distance between two PCBs, inlet-screen gap and screen thickness. A correlation for the static anddynamic pressure drop, the percentage of dimensionless wetted area, Aw*, and the RMS* factor (a function of the flow uniformity along the PCB) after the screen is reported as a function of six geometrical dimensionless parameters and the Reynolds number. The correlations, that are based on 174 three dimensional simulations, yield good results for the total pressure drop, in which the values are predicted within the interval of ±15%. For the, Aw* all the predicted values are within the interval of ±22% of the observed values. Finally, for the RMS* factor, the majority of the values also have a disagreement of less than 20% of the observed values. These last two parameters are believed to provide a correct insight about the flow pattern after the screen.

Keyword
Electromagnetic compatibility (EMC) screen, Flow pattern, K-ε, Perforated plate, Porosity, Pressure drop, Renormalization group (RNG), Subrack, Wetted area
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-6736 (URN)10.1109/TCAPT.2009.2013337 (DOI)000263928700018 ()2-s2.0-63049102684 (Scopus ID)
Note
QC 20100630. Uppdaterad från Submitted till Published (20100908)Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2017-12-14Bibliographically approved
7. Compact CFD modelling of EMC screen for radio base stations: a porous media approach and a correlation for the directional loss coefficients
Open this publication in new window or tab >>Compact CFD modelling of EMC screen for radio base stations: a porous media approach and a correlation for the directional loss coefficients
2007 (English)In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 30, no 4, 875-885 p.Article in journal (Refereed) Published
Abstract [en]

A methodology to obtain the directional pressure loss coefficients in a porous media model of an electromagnetically compatible screen of a radio base station model is presented. The directional loss coefficients of this compact model are validated against a detailed computational fluid dynamics model not only by comparing the total pressure drop, but also by evaluating the flow pattern after the screen. The detailed model was validated in an earlier article by the authors. A parametric study is conducted for 174 cases. Seven parameters were investigated: velocity, inlet height, screen porosity, printed circuit board (PCB) thickness, inlet-screen gap, distance between two PCBs and screen thickness. Based on the compact model parametric study, two correlations for the directional loss coefficients are developed as a function of the Reynolds number and the above geometrical parameters. The average disagreement between the compact model that uses the directional loss coefficients from the correlations and the detailed model was of 3% for the prediction of the total pressure drop and less than 6.5% and 9.5% for two coefficients that accurately characterize the flow pattern.

Place, publisher, year, edition, pages
IEEE Press, 2007
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6737 (URN)10.1109/TCAPT.2007.910065 (DOI)000251431100042 ()2-s2.0-36949028784 (Scopus ID)
Note

Updated from "Accepted" to "Published". QC 20150702

Available from: 2007-01-11 Created: 2007-01-11 Last updated: 2017-12-14Bibliographically approved

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CiteExportLink to record
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