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Discharge coefficient of centre-pivot roof windows
Danish Building Research Institute, Aalborg University, Copenhagen, Denmark .
Danish Building Research Institute, Aalborg University, Copenhagen, Denmark .
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering. (Inomhusmiljö)
Indoor Environmental Engineering, Aalborg University, Aalborg, Denmark .
2015 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, 635-643 p.Article in journal (Refereed) Published
Abstract [en]

Use of centre-pivot roof windows is very common in single family houses in Nordic Europe. Unfortunately the wind-driven airflow characteristics of this kind of windows are missing in the scientific literature. In the present study, the airflow rate through the window was specified by using the discharge coefficient. Wind tunnel measurements using a modelled centre-pivot roof windowwas used in the present study. For smaller sash opening angles the value of discharge coefficientwas approaching unity and the discharge coefficient decreased with increase in the sash opening angle. The value of 0.6 was only obtained when the window was without sash. Hence, the inclusion of sash improved the airflow characteristics of the window due to increased value of the dischargecoefficient. The discharge coefficient also depended on turbulence in the flow. In the absence of external wind, the turbulence was described by the value of Re. Only for higher values of Re the still-air discharge coefficients became independent of the flow direction and the air velocity. Whereas for wind driven natural ventilation the ratio of average air speed within the opening and the reference wind speed (velocity ratio) was used to define the fully developed turbulent flow. Constant values of wind-driven discharge coefficients were obtained when the average air speed within the opening was equal to or greater than the reference wind speed i.e. the velocity ratio greater than unity. Moreover, when the velocity ratio was greater than unity, the still-air discharge coefficients became identical to the wind-driven discharge coefficients.

Place, publisher, year, edition, pages
2015. Vol. 92, 635-643 p.
Keyword [en]
Centre-pivot roof window, Discharge coefficient, Wind tunnel
National Category
Fluid Mechanics and Acoustics Building Technologies
URN: urn:nbn:se:hig:diva-19693DOI: 10.1016/j.buildenv.2015.05.034ISI: 000358807800056ScopusID: 2-s2.0-84935038665OAI: oai:DiVA.org:hig-19693DiVA: diva2:822233
Available from: 2015-06-16 Created: 2015-06-16 Last updated: 2015-09-04Bibliographically approved

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