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Comparison of the Behavior of Foams and Gels Exposed to Fire.


pdf icon Comparison of the Behavior of Foams and Gels Exposed to Fire. (250 K)
Tafreshi, A. M.; diMarzo, M.

NISTIR 6242; October 1998.

National Institute of Standards and Technology. Annual Conference on Fire Research: Book of Abstracts. November 2-5, 1998, Gaithersburg, MD, Beall, K. A., Editor(s), 59-60 pp, 1998.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB99-102519

Keywords:

fire research; fire science; fire suppression; foam extinguishing systems; fire behavior; gels; experiments; fire protection

Abstract:

Water is the principal component of both foams and gels used as fire protection agents. The foam is expanded to several times its original liquid volume with air. Data from a previous study show that, when the foam is subjected to a radiant heat input of 18 kW/m2, the peak of the radiant heat absorption is at about 30 mm in the depth of the foam layer while radiant heat penetrates to depths up to 60 mm. The reason for this behavior is the decreasing density of the foam near its exposed surface as the water is evaporated away from the foam matrix. As the density decrease, so does the extinction coefficient leading to lower absorption of the incoming radiation. In the depth of the foam layer, as the thickness and the density both increase, the radiant heat is absorbed causing the water to vaporize in-situ since the contribution of thermal diffusion is small. In contrast with this phenomenology, the behavior of the gel, in a similar situation, is dominated by thermal diffusion. The radiant heat input is absorbed in the immediate proximity of the gel surface and the exposed surface approaches saturation conditions for the duration of the transient. These differences result in significantly different fire protection behaviors. These observations complemented with other, more qualitative considerations will identify a rationale for recommending the proper agent for the specific fire protection scenario.