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Entrainment and its Implications on Microclimate Ventilation Systems: Scaling the Velocity and Temperature Field of a Round Free Jet
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.ORCID iD: 0000-0002-2171-3013
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
2019 (English)In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 29, no 2, p. 331-346Article in journal (Refereed) Published
Abstract [en]

Research on microclimate ventilation systems, which mostly involve free jets, point to delivery of better ventilation in breathing zones. While the literature is comprehensive, the influence of contaminant entrainment in jet flows and its implications on the delivery of supplied air is not fully addressed. This paper present and discuss entrainment characteristics of a jet issued from a round nozzle (0.05 m diameter), in relation to ventilation, by exploring the velocity and temperature fields of the jet flow. The results show a trend suggesting that increasing the Reynolds number (Re) reduces ambient entrainment. As shown herein, about 30% concentration of ambient air entrained into the bulk jet flow at Re 2541 while Re 9233 had about 13% and 19% for Re = 6537/12026 at downstream distance of 8 diameters (40 cm). The study discusses that “moderate to high” Re may be ideal to reduce contaminant entrainment, but this is limited by delivery distance and possibly the risk of occupant discomfort. Incorporating the entrainment mixing factor (the ratio of room contaminants entrained into a jet flow) in performance measurements is proposed and further studies are recommended to verify results herein and test whether this is general to other nozzle configurations.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019. Vol. 29, no 2, p. 331-346
Keywords [en]
Entrainment, Round free jet, Microclimate ventilation systems, Temperature field, Velocity field, Entrainment mixing factor
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:hig:diva-28736DOI: 10.1111/ina.12524ISI: 000459637200016PubMedID: 30500986Scopus ID: 2-s2.0-85059514934OAI: oai:DiVA.org:hig-28736DiVA, id: diva2:1267372
Available from: 2018-12-02 Created: 2018-12-02 Last updated: 2019-08-12Bibliographically approved

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The full text will be freely available from 2019-11-30 00:01
Available from 2019-11-30 00:01

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Kabanshi, AlanSandberg, Mats

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