File Download

There are no files associated with this item.

  Links for fulltext
     (May Require Subscription)
Supplementary

Article: Age of air and air exchange efficiency in high-rise urban areas and its link to pollutant dilution

TitleAge of air and air exchange efficiency in high-rise urban areas and its link to pollutant dilution
Authors
KeywordsAge of air
Air exchange efficiency
Building area density
High-rise building array
Homogeneous emission method
Numerical simulation
Issue Date2011
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/atmosenv
Citation
Atmospheric Environment, 2011, v. 45 n. 31, p. 5572-5585 How to Cite?
AbstractBy means of computational fluid dynamic (CFD) simulations, this paper investigated how rural winds transport relatively clean air into high-rise urban areas to dilute airborne pollutants. Two ventilation concepts for indoor environments were applied: the age of air to quantify the time taken by rural young air to reach a given place after it enters an urban area and the air exchange efficiency to evaluate the efficiency of rural winds flushing the entire urban canopy layer. Several square building arrays with street aspect ratios (building height/street width, H/. W) ranging from 1.5 to 5.3 and building area densities of 0.25 (medium) or 0.4 (compact) were considered as the approaching wind is parallel to the main street whose length varies from street scales to neighborhood scales (330-510 m to 1.03-1.65 km in full-scale).Results show that considerable young rural air enters windward entries but a major fraction of air is vertically driven out as flowing deeper into such high-rise building arrays. So air exchange efficiencies are less than 50% in street-scale arrays, and smaller in longer (neighborhood-scale) or narrower arrays. For the neighborhood-scale medium arrays, considering the power-law velocity profile in the upstream free flow, a taller array gains a larger inflow rate across its windward entry and experiences younger air and greater air exchange efficiency than a lower one. If all buildings are theoretically open-based in a neighborhood-scale compact array, air becomes much younger everywhere and the air exchange efficiency doubles. In arrays of buildings with different heights, the secondary streets in front of taller buildings get younger air due to the downward flows within them. Although further investigations are still required before providing a practical framework, this paper is one of the first attempts to find ways in improving the ventilation performance in high-rise cities like Hong Kong. © 2011.
Persistent Identifierhttp://hdl.handle.net/10722/139378
ISSN
2015 Impact Factor: 3.459
2015 SCImago Journal Rankings: 1.999
ISI Accession Number ID
Funding AgencyGrant Number
University of Hong Kong on Initiative of Clean Energy for Environment
Funding Information:

The work in this paper is supported by a University Development Fund from the University of Hong Kong on Initiative of Clean Energy for Environment. The help from Prof Mats Sandberg in KTH research school Sweden in wind tunnel tests is highly acknowledged.

References

 

DC FieldValueLanguage
dc.contributor.authorHang, Jen_HK
dc.contributor.authorLi, Yen_HK
dc.date.accessioned2011-09-23T05:49:00Z-
dc.date.available2011-09-23T05:49:00Z-
dc.date.issued2011en_HK
dc.identifier.citationAtmospheric Environment, 2011, v. 45 n. 31, p. 5572-5585en_HK
dc.identifier.issn1352-2310en_HK
dc.identifier.urihttp://hdl.handle.net/10722/139378-
dc.description.abstractBy means of computational fluid dynamic (CFD) simulations, this paper investigated how rural winds transport relatively clean air into high-rise urban areas to dilute airborne pollutants. Two ventilation concepts for indoor environments were applied: the age of air to quantify the time taken by rural young air to reach a given place after it enters an urban area and the air exchange efficiency to evaluate the efficiency of rural winds flushing the entire urban canopy layer. Several square building arrays with street aspect ratios (building height/street width, H/. W) ranging from 1.5 to 5.3 and building area densities of 0.25 (medium) or 0.4 (compact) were considered as the approaching wind is parallel to the main street whose length varies from street scales to neighborhood scales (330-510 m to 1.03-1.65 km in full-scale).Results show that considerable young rural air enters windward entries but a major fraction of air is vertically driven out as flowing deeper into such high-rise building arrays. So air exchange efficiencies are less than 50% in street-scale arrays, and smaller in longer (neighborhood-scale) or narrower arrays. For the neighborhood-scale medium arrays, considering the power-law velocity profile in the upstream free flow, a taller array gains a larger inflow rate across its windward entry and experiences younger air and greater air exchange efficiency than a lower one. If all buildings are theoretically open-based in a neighborhood-scale compact array, air becomes much younger everywhere and the air exchange efficiency doubles. In arrays of buildings with different heights, the secondary streets in front of taller buildings get younger air due to the downward flows within them. Although further investigations are still required before providing a practical framework, this paper is one of the first attempts to find ways in improving the ventilation performance in high-rise cities like Hong Kong. © 2011.en_HK
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/atmosenven_HK
dc.relation.ispartofAtmospheric Environmenten_HK
dc.subjectAge of airen_HK
dc.subjectAir exchange efficiencyen_HK
dc.subjectBuilding area densityen_HK
dc.subjectHigh-rise building arrayen_HK
dc.subjectHomogeneous emission methoden_HK
dc.subjectNumerical simulationen_HK
dc.titleAge of air and air exchange efficiency in high-rise urban areas and its link to pollutant dilutionen_HK
dc.typeArticleen_HK
dc.identifier.emailLi, Y:liyg@hkucc.hku.hken_HK
dc.identifier.authorityLi, Y=rp00151en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.atmosenv.2011.04.051en_HK
dc.identifier.scopuseid_2-s2.0-80051472413en_HK
dc.identifier.hkuros193891en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-80051472413&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume45en_HK
dc.identifier.issue31en_HK
dc.identifier.spage5572en_HK
dc.identifier.epage5585en_HK
dc.identifier.isiWOS:000295070300020-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridHang, J=35240092500en_HK
dc.identifier.scopusauthoridLi, Y=7502094052en_HK

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats