Effect of Minute Water Droplets on a Simulated Sprinkler Link Thermal Response.
Effect of Minute Water Droplets on a Simulated Sprinkler
Link Thermal Response.
Gavelli, F.; Ruffino, P.; Anderson, G.; diMarzo, M.
NIST GCR 99-776; 117 p. July 1999.
Sponsor:National Institute of Standards and Technology,
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
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.