- Author
- Tan, Q. | Jaluria, Y.
- Title
- Flow Through a Horizontal Vent in an Enclosure Fire.
- Coporate
- Rutgers, State University of New Jersey, New Brunswick
- Sponsor
- National Institute of Standards and Technology, Gaithersburg, MD
- Contract
- NIST-GRANT-60NANB7D0743
- Book or Conf
- American Society of Mechanical Engineers (ASME). Heat Transfer in Fire and Combustion Systems. HTD-Vol. 199. 1992, Am. Soc. of Mechanical Engineers, New York, NY, 115-122 p., 1992
- Keywords
- enclosures | vents | air flow | combustion products | compartments | flow rate
- Identifiers
- non-zero pressure; density differences
- Abstract
- The flow of air and combustion products across vents governs the growth and spread of fires in compartments and buildings. The rate of inflow of oxygen from the ambient determines the combustion process and the energy release rate in fires for many practical circumstances. Similarly, the spread of the fire to adjoining areas is strongly dependent on the resulting flow through vents. Horizontal vents are important in many situations, particularly in multi-room compartments, ships and containment buildings. This paper considers the flow through such vents for non-zero pressure and density differences that usually arise across the vent in typical fires. A detailed experimental study is undertaken to understand the basic nature of the flow through a horizontal vent, using fresh and saline water to simulate the density differences that arise in fires due to temperature rise in the enclosure. An externally imposed pressure difference is exerted and the resulting flow rates are measured for a wide range of vent dimensions. In the absence of a pressure difference, a bi-directional flow arises due to buoyancy effects. As the pressure increases, the flow gradually shifts to a uni-directional flow. The flow rate at relatively large pressure differences can be obtained from existing vent flow models that are based on Bernoulli's equation. However, typical fire conditions lie in the region where both buoyancy and pressure effects are important. There is very little information available in the literature on this flow regime. The paper presents results on the measured flow rates and also some correlations that consolidate the observed trends. Finally, typical fires in rooms with horizontal vents are examined. The results obtained are considered with respect to the growth and development of fires in vented enclosures, different regimes that may arise and possible periodic variations that have been observed in room fires for certain circumstances.