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Calculating Combined Buoyancy- and Pressure-Driven Flow Through a Shallow, Horizontal, Circular Vent: Application to a Problem of Steady Burning in a Ceiling-Vented Enclosure.


pdf icon Calculating Combined Buoyancy- and Pressure-Driven Flow Through a Shallow, Horizontal, Circular Vent: Application to a Problem of Steady Burning in a Ceiling-Vented Enclosure. (727 K)
Cooper, L. Y.

Fire Safety Journal, Vol. 27, 23-35, 1996.

Keywords:

fire research; vents; buoyancy; pressure; ceilings; enclosures; algorithms; equations; energy release rate; ships; wood; ceiling vents; oxygen concentration

Abstract:

A model was developed previously for calculating combined buoyancy- and pressure-driven (i.e., forced) flow through a shallow, circular, horizontal vent where the vent-connected spaces are filled with fluids of different density in an unstable configuration (density of the top fluid is larger than that of the bottom). In this paper, the model is summarized and then applied to the problem of steady burning in a ceiling-vented enclosure where normal atmospheric conditions characterize the upper-space environment. Such fire scenarios are seen to involve a zero to relatively moderate cross-vent pressure difference and bidirectional exchange flow between the enclosure and the upper space. A solution to the problem leads to a general result that relates the rate of energy release of the fire to the area of the vent and the temperature and oxygen concentration of the upper portion of the enclosure environment. This result is seen to be consistent with previously published data from experiments involving ceiling-vented fire scenarios.