Paper 4
Buoyancy Driven Natural Ventilation
through Horizontal Openings
Per
Heiselberg1 and
Zhigang Li2
1Division
of Architectural Engineering, Department of Civil Engineering, Aalborg
University,
Aalborg, Denmark
2Danfoss
A/S, Nordborg, Denmark
Abstract
An experimental study of the phenomenon of buoyancy driven natural
ventilation through single-sided horizontal openings was performed in a
full-scale laboratory test rig. The measurements were made for opening
ratios L/D ranging from 0.027 to 4.455, where L and D are the length of
the opening and the diameter of the opening, respectively. The basic
nature of airflow through single-sided openings, including airflow rate,
air velocity, temperature difference between the rooms and the dimensions
of the horizontal openings, were measured. A bi-directional airflow rate
was measured using the constant injection tracer gas technique. Smoke
visualizations showed that the airflow patterns are highly transient and
unstable, and that the airflow rate oscillates with time. Correlations
between the Froude (Archimedes) number Fr (Ar) and the L/D ratio are
presented. In some cases the measured airflow rates fit quite well with
the Epstein's formula but in other cases the measured data show clear
deviations from the Epstein's formula. Thus, revised formulas for natural
ventilation are proposed.
Key words: natural ventilation, airflow rate, buoyancy,
horizontal opening, tracer gas, LES.
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