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Collision Dynamics of A Liquid Fire Suppressant Upon A Heated Wax Surface.


pdf icon Collision Dynamics of A Liquid Fire Suppressant Upon A Heated Wax Surface. (3053 K)
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.

Keywords:

droplets; fire suppression

Abstract:

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.