Collision Dynamics of A Liquid Fire Suppressant Upon A Heated Wax Surface.
Collision Dynamics of A Liquid Fire Suppressant Upon A
Heated Wax Surface.
Manzello, S. L.; Yang, J. C.
International Conference on Liquid Atomisation and Spray
Systems (ICLASS), 9th Conference. Proceedings. July
13-18, 2003, Sorrento, Italy, 1-8 pp, 2003.
droplets; fire suppression
The impact of a distilled water droplet upon a heated
wax surface was investigated experimentally using a
high-speed digital camera at 1000 frames/s. Two
different droplet impact Weber numbers (We) were
considered and the collision dynamics were investigated
with the temperature of the wax surface varied from 20 C
to 75 C. For each impact We number, the evolution of the
liquid film diameter was measured as a function of
surface temperature. At We = 27, the evolution of the
liquid film diameter displayed three distinct regimes:
spreading, retraction, and secondary spreading. The
liquid film diameter was observed to recoil faster as
the surface temperature of the wax was increased. The
increase in recoil speed was accompanied by a reduction
in the effective Ohnesorge number (Oh). At We = 150, as
the droplet recoiled, an unstable column of fluid was
observed to rise above the wax surface. The instability
of the fluid column at We = 150 was explained using
Rayleigh instability theory. At 75 C, the melting point
of the wax, collision dynamics were qualitatively
similar to droplet impact on a liquid surface.