Effect of Beamed, Sloped, and Sloped Beamed Ceilings on the Activation TIme of a Residential Sprinkler.
Effect of Beamed, Sloped, and Sloped Beamed Ceilings on
the Activation TIme of a Residential Sprinkler.
Vettori, R. L.
NISTIR 7079; 45 p. December 2003.
Sponsor:Federal Emergency Management Agency, Washington, DC
Available from:Orders Only) 800-553-6847;
sprinklers; ceilings; activation time; residential
buildings; beams; ceiling jets; computer models; fire
models; sprinkler response; sprinkler systems
A series of 72 experiments was conducted to compare the
effects of beamed, sloped, and sloped beamed ceilings on
the activation times of a quick response residential
pendent sprinkler. Six different geometries were
studied. The geometries included a smooth horizontal
ceiling, a horizontal beamed ceiling, a smooth ceiling
with a slope of 13, a beamed ceiling with a slope of 13,
a smooth ceiling with a slope of 24, and a beamed
ceiling with a slope of 24. For each configuration, the
fire source, a computer controlled methane gas burner,
was placed in three different locations. Additionally,
for each burner location, the flow of methane gas to the
burner was supplied in such a way as to give two
different fire growth rates. For each ceiling
configuration and fire growth rate two experiments were
performed. Measurements taken include the time to
sprinkler activation, temperature and velocity of the
ceiling jet at the sprinkler of activation, and
temperatures at various other locations and elevations
within the fire compartment. Additionally, all
geometries were modeled using the National Institute of
Standards and Technology (NIST) computational fluid
dynamics fire model Fire Dynamics Simulator (FDS) to
compare predicted results with the test data obtained.
It was found in a majority of cases that simply sloping
the ceiling to an angle of 13 or 24 decreased the
activation time of the sprinkler when compared to a
smooth horizontal ceiling. However adding beams to the
ceiling caused an increase in sprinkler activation time
in all but three cases. For the Fire Dynamics Simulator
model, the best prediction was the beamed ceiling sloped
at 24 where model predictions were within an average of
4 % of measured times. The worst case for model
prediction was the smooth ceiling sloped at 13; in these
cases Fire Dynamics Simulator predicted activation times
within an average of 26% of measured times.