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Effect of Minute Water Droplets on a Simulated Sprinkler Link Thermal Response.

pdf icon Effect of Minute Water Droplets on a Simulated Sprinkler Link Thermal Response. (5864 K)
Gavelli, F.; Ruffino, P.; Anderson, G.; diMarzo, M.

NIST GCR 99-776; 117 p. July 1999.


National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Order number: PB99-159907


sprinklers; droplets; water sprays; thermal response; ceilings; fire models; fire plumes; heat transfer; thermal analysis; evaporation cooling; sprinkler response; nozzles; temperature measurements; gas burners; response time


This report presents the derivation of an improved model for the prediction of the transient thermal response of a ceiling-mounted fire detection sprinkler link in the event of a fire. The model expands the range of applicability of the current approach to include the presence of minute water droplets being carried by the hot gas plume. This situation has been observed experimentally in situations where a fire develops in an enclosed space equipped with an array of sprinklers: the activation of the first sprinkler releases a fine water spray, part of which is entrained by the rising plume and affects the operation of the surrounding devices. A new test facility has been built in order to verify the proposed model, as well as to investigate, in a controlled environment, the effect of the water droplets on different sprinkler links. The experimental results indicate that the model is able to describe the transient response of a sprinkler link immersed in a two-phase flow of hot gas and water droplets, and the assumptions made in deriving such model have been verified. Compatibility with the current sprinkler response model, in the absence of water droplets in the stream, has also been verified. Finally, numerical values have been obtained for the constants introduced with the proposed model. Future enhancements of the instrumentation capabilities will allow to broaden the range of conditions that can be tested.