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Inflow Of Air Required At Wall And Ceiling Apertures To Prevent Escape Of Fire Smoke

Heskestad, G. and Spaulding, R.D., 1991. Inflow Of Air Required At Wall And Ceiling Apertures To Prevent Escape Of Fire Smoke. Fire Safety Science 3: 919-928. doi:10.3801/IAFSS.FSS.3-919


Experiments have been conducted to determine critical Froude numbers associated with required inflow of air to a fire space through wall and ceiling apertures to prevent escape of smoke. The experiments were conducted mostly on reduced, model scale, with verification i n a 2.4 m high test room. Critical Froude numbers, as formulated, were insensitive to aperture geometry. Those for wall apertures varied slowly and predictably with the vertical temperature distribution i n the room, consistent with a discharge coefficient of 0.64 for the inflow. Those for ceiling apertures exhibited a dependence on an aperture Grashof number, with both a high- Grashof number asymptote and an aperture low-Grashof number asymptote. While discharge coefficients for wall apertures can be considered constant near 0.64 for aperture Froude numbers larger than critical , the discharge coefficient for ceiling apertures increased from 0.19 near the critical Froude number, toward the familiar isothermal value for sharp-edged orifices of 0.61 near a Froude number seven times larger than the critical.


compartment fires, smoke control, apertures, discharge coefficient

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