NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Calculating Combined Buoyancy- and Pressure-Driven Flow Through a Shallow, Horizontal, Circular Vent; Application to 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 Problem of Steady Burning in a Ceiling-Vented Enclosure. (523 K)
Cooper, L. Y.

National Institute of Standards and Technology (NIST) and Society of Fire Protection Engineers (SFPE). International Conference on Fire Research and Engineering (ICFRE). Proceedings. September 10-15, 1995, Orlando, FL, SFPE, Boston, MA, Lund, D. P.; Angell, E. A., Editors, 321-326 pp, 1995 AND European Symposium on Fire Safety Science, First (1st). ABSTRACTS. Proceedings. Session II. Fire Dynamics 2. ETH Institute for Structural Engineering. August 21-23, 1995, Zurich, Switzerland, II-17/99-99 pp, 1995.

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 equations are 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 bi-directional exchange flow between the enclosure and the upper space. A general solution to the problem is obtained. This relates the rate of energy release of the fire to the area of the vent and to the temperature and oxygen concentration of the upper portion of the enclosure environment. The solution is seen to be consistent with previously-published data involving ceiling-vented fire scenarios.