Spray Characteristics of Fire Sprinklers.
Spray Characteristics of Fire Sprinklers.
(2455 K)
Sheppard, D. T.
NIST GCR 02-838; Thesis; 204 p. June 2002.
Order number: PB2003-100879
Keywords:
sprinklers; sprays; water distribution; droplets; drop
sizes; lasers; experiments; velocity; pressure effect
Abstract:
Although fire sprinklers have been in use for over 100
years there has been little progress toward developing
analytical methods of calculating their effectiveness.
This lack of progress is primarily due to absence of
information about initial spray characteristics near
sprinklers. In this study, experiments were conducted
near a variety of sprinkler designs utilizing 1) a
pulsed laser sheet and CCD camera and 2) phase Doppler
interferometry. Particle image velocity analysis of the
CCD camera images has shown that velocities near the
sprinklers can be described as a purely radial flow with
the origin located between the orifice and deflector for
pendant sprinklers and between the orifice and slightly
above the deflector for upright sprinklers. The average
radial droplet velocity at a distance 0.2m from the
sprinkler orifice is 54% of the water velocity through
the orifice with a 0.8% standard deviation. The maximum
spray velocities ranged from 62% to 120% of the orifice
water velocity with a statistically significant trend
for higher maximum velocities from pendant sprinklers.
The radial velocity is strongly dependent on the
elevation angle and less dependent on the azimuthal
angle. The radial velocity is a function of the
specific sprinkler model, so a general description of
the radial velocity independent of sprinkler model is
not very accurate. The radial droplet velocity is
proportional to square root of the water pressure
entering the sprinkler.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899