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Kårekull, O., Efraimsson, G. & Åbom, M. (2015). CHALLENGES AND OPPORTUNITIES FOR FLOW NOISE PREDICTION IN HVAC SYSTEMS. In: : . Paper presented at INTERNATIONAL CONFERENCE ON FAN NOISE, TECHNOLOGY AND NUMERICAL METHODS, 15-17 APRIL 2015 L’Espace Tête d’Or, Lyon, France.
Open this publication in new window or tab >>CHALLENGES AND OPPORTUNITIES FOR FLOW NOISE PREDICTION IN HVAC SYSTEMS
2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates the possibilities of noise prediction in Heating Ventilation and Air Conditioning (HVAC) systems using semi empirical scaling laws. An approach is presented where the general noise reference spectra are combined with Reynolds Average Navier Stokes (RANS) simulations. Focus is at applying the suggested noise prediction approach to common HVAC components but also to discuss the properties of the prediction model, e.g. radiation characteristics and chosen reference spectra. A model is presented, using a momentum flux assumption of the noise sources, which is validated by a range of HVAC components of both high and low pressure loss.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-166205 (URN)2-s2.0-85048964686 (Scopus ID)
Conference
INTERNATIONAL CONFERENCE ON FAN NOISE, TECHNOLOGY AND NUMERICAL METHODS, 15-17 APRIL 2015 L’Espace Tête d’Or, Lyon, France
Funder
Swedish Research Council Formas, 245-2011-1615
Note

QC 20150615

Available from: 2015-05-05 Created: 2015-05-05 Last updated: 2018-12-10Bibliographically approved
Kårekull, O. (2015). Predicting flow-generated noise from HVAC components. (Licentiate dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Predicting flow-generated noise from HVAC components
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

More energy efficient fans, i.e. larger sizes running at lower speeds, in Heating Ventilation and Air Conditioning (HVAC) systems decrease the fan noise and increase the importance of flow generated noise in other system components, e.g., dampers and air terminal devices. In this thesis, an extended prediction model, using semi-empirical scaling laws, for flow noise prediction in HVAC systems at low Mach number flow speeds is presented. The scaling laws can be seen as a combination of a generalized noise spectrum based on experimental data and constriction flow characteristics, where the latter can be gained from ComputationalFluid Dynamics (CFD) simulations. The flow generated noise can be predicted by semi-empirical scaling laws to avoid a time consuming, fully resolved simulation or measurement. Here, an approach is suggested where the general noise spectra are combined with turbulent data obtained from Reynolds Average Navier Stokes (RANS) simulations. A model is proposed using a momentumflux assumption of the dipole source strength and a frequency scaling based on the constriction pressure loss. To evaluate the applicability of the semi-emprical scaling law on different HVAC geometries both literature data and new measurement data are considered. Focus is at comparing geometries of high and low pressure loss but also to discuss the differences in other properties, e.g. radiation characteristics. A general noise reference spectrum is determined bya best fit calculation of measurement data including orifice, damper and bend geometries. Air terminal devices at the end of a duct are also evaluated and compared to constrictions inside ducts. The expected accuracy of the suggested model and its challenges as a tool for flow noise prediction of non-rotating components in HVAC systems are discussed.

Abstract [sv]

På grund av ökade energieffektivitetskrav har större fläktar som roterar med lägre hastighet börjat användas i byggnaders ventilationssystem(HVAC). De lägre hastigheterna har minskat ljudnivån från fläkten och ökat betydelsen av strömningsalstrat ljud från andra systemkomponenter, t.ex. spjäll och luftdon. I denna avhandling presenteras en förbättrad prediktionsmodell, utifrån semi-empiriska skalningslagar, för strömningsalstrat ljud i ventilationssystem. Skalningslagarna kan ses som en kombination av generellaljudspektra och strypningens specifika flödesegenskaper, där det senare kan fås från Computational Fluid Dynamics (CFD) simuleringar. Semiempiriska skalningslagar är ett alternativ för att undvika tidskrävandemätningar eller fullt upplösta simuleringar. Ett tillvägagångssätt presenteras här där det generella spektrat, bestämt utifrån experimentell data, kombineras med data från Reynolds Average Navier Stokes (RANS) simuleringar. En prediktionsmodell föreslås där källstyrkan hos dipolkrafterna definieras utifrån rörelsemängd och frekvensskalningen utifrån strypningens tryckfall. För att utvärdera vilka HVAC geometrier som kan ingå i den generella modellen analyseras både resultat från litteraturen samt nya mätningar. Avhandlingsarbetet fokuserar på att jämföra geometrier av högt och lågt tryckfall men också på att diskutera skillnader i andra egenskaper såsom strålningskarakteristik t.ex. genom att jämföra luftdon i slutet av en kanal med strypningar inuti kanalen. Ett generellt ljudspektrum föreslås utifrån en anpassning av mätdata för strypningar, spjäll och böjar. Modellens förväntade noggrannhet och dess utmaningar som prediktionsverktyg för icke-roterande komponenter i ventilationssystem diskuteras.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. p. v, 46
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:22
Keywords
flow noise, noise prediction, HVAC, flödesalstrat ljud, bullerprediktion, HVAC
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-166201 (URN)978-91-7595-564-3 (ISBN)
Presentation
2015-05-27, sal Munin, Teknikringen 8, BV, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, 245-2011-1615
Note

QC 20150518

Available from: 2015-05-18 Created: 2015-05-05 Last updated: 2015-05-18Bibliographically approved
Kårekull, O., Efraimsson, G. & Åbom, M. (2015). Revisiting the Nelson-Morfey scaling law for flow noise from duct constrictions. Journal of Sound and Vibration, 357, 233-244
Open this publication in new window or tab >>Revisiting the Nelson-Morfey scaling law for flow noise from duct constrictions
2015 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 357, p. 233-244Article in journal (Refereed) Published
Abstract [en]

The semi empirical scaling law by Nelson and Morfey [1] predicts the noise generation from constrictions in ducts with low Mach number flows. The results presented here demonstrate that the original model loose accuracy for constrictions of high pressure loss. An extension based on a momentum flux assumption of the dipole forces is suggested and is evaluated against measurement results for orifice geometries of higher pressure loss than earlier evaluated. A prediction model including constrictions at flow duct terminations is also suggested. Improved accuracy for the predictions of the new model are found for orifice geometries of both high and low pressure loss inside and at end of ducts. The extended model is finally evaluated by measurementson a regular ventilation air terminal device.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-166200 (URN)10.1016/j.jsv.2015.06.019 (DOI)000360965200015 ()2-s2.0-84940889140 (Scopus ID)
Funder
Swedish Research Council Formas, 245-2011-1615
Note

Updated from manuscript to article.

QC 20151009

Available from: 2015-05-05 Created: 2015-05-05 Last updated: 2017-12-04Bibliographically approved
Kårekull, O., Efraimsson, G. & Åbom, M. (2014). Prediction model of flow duct constriction noise. Applied Acoustics, 82, 45-52
Open this publication in new window or tab >>Prediction model of flow duct constriction noise
2014 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 82, p. 45-52Article in journal (Refereed) Published
Abstract [en]

The scaling law for aerodynamic dipole type of sound from constrictions in low speed flow ducts by Nelson and Morfey is revisited. A summary of earlier published results using this scaling law is presented together with some new data. Based on this, an effort to find a general scaling law for the sound power for components with both distinct and non-distinct flow separation points are made. Special care is taken to apply the same scaling to all data based on the pressure drop. Results from both rectangular and circular ducts, duct flow velocities from 2 to 120 m/s and sound power measurements made both in ducts and in reverberation chambers are presented. The computed sound power represents the downstream source output in a reflection free duct. In particular for the low frequency plane wave range strong reflections from e.g. openings can affect the sound power output. This is handled by reformulating the Nelson and Morfey model in the form of an active acoustic 2-port. The pressure loss information needed for the semi-empirical scaling law can be gained from CFD simulations. A method using Reynold Average Navier Stokes (RANS) simulations is presented, where the required mesh quality is evaluated and estimation of the dipole source strength via the use of the pressure drop is compared to using the turbulent kinetic energy.

Keywords
Flow noise, Noise prediction, RANS
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-147018 (URN)10.1016/j.apacoust.2014.03.001 (DOI)000336117500007 ()2-s2.0-84897514407 (Scopus ID)
Funder
Formas, 245-2011-1615
Note

QC 20140625

Available from: 2014-06-25 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
Kårekull, O. & Efraimsson, G. (2013). Comparison of RANS parameters for flow noise prediction. In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life. Paper presented at 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013 (pp. 5916-5925). OAL-Osterreichischer Arbeitsring fur Larmbekampfung
Open this publication in new window or tab >>Comparison of RANS parameters for flow noise prediction
2013 (English)In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life, OAL-Osterreichischer Arbeitsring fur Larmbekampfung , 2013, p. 5916-5925Conference paper, Published paper (Refereed)
Abstract [en]

TThe use of Computational Fluid Dynamics (CFD) and especially Reynolds Averaged Navier Stokes Equations (RANS) simulations is a well-established tool in industry for performance evaluation of constrictions in low speed flow ducts. However, the use of CFD simulations for noise predictions is not as common. In this paper, two different models to predict the sound spectra through the use of RANS simulations and a noise reference spectrum are compared and evaluated. One method predicts the sound based on the pressure drop whereas the other method is based on the turbulent kinetic energy. The influence of both turbulence models as well as mesh properties have been investigated. Noise predictions from simulation results are compared to noise measurement results of an orifice in a duct. The comparison between the simulated results and measured data are in excellent agreement. The benefit of using the pressure drop, as input data, is a lower sensitivity to both the structure and the resolution of the mesh. Also, this model has a more general definition allowing a consistent method for different constriction geometries. Still, predictions using the turbulent kinetic energy result in equivalent accuracy and even if the choice of input data is more complex it can be preferred in special cases.

Place, publisher, year, edition, pages
OAL-Osterreichischer Arbeitsring fur Larmbekampfung, 2013
Keywords
Flow noise, Noise prediction, RANS
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:kth:diva-137968 (URN)2-s2.0-84904498256 (Scopus ID)978-163266267-5 (ISBN)
Conference
42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013
Funder
Formas, 245-2011-1615
Note

QC 20140228

Available from: 2013-12-17 Created: 2013-12-17 Last updated: 2014-09-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6811-056X

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