Liquid or Solid on Liquid in Leidenfrost Film Boiling
Film-boiling heat transfer between two liquids at different temperatures has been under extensive investigation recently in consideration of propellant-spillage accidents . If liquid propellants spill accidently during test-stand or launching operations, a catastrophic explosion resulting from the detonation of the fuel and oxidizer is possible. In particular, a number of experiments  have been performed involving the mixing of small kerosene spheres in liquid oxygen. When small kerosene spheres are dispersed in a matrix of liquid oxygen, the sensible heat of the kerosene spheres vaporizes the liquid oxygen, thereby forming a film of oxygen vapor around the sphere. In film boiling, the vaporization rates are one or more orders of magnitude less than those of peak-nucleate boiling. In nucleate boiling, extreme turbulence and mixing will occur because of the large amount of vapor sporadically generated at the interface. On the other hand, film boiling is a relatively quiescent phenomenon, and as such can have a significant damping effect on the explosive potential of the mixture. The encapsulation of the liquid sphere (as it freezes), as shown herein, can also provide significant damping.
KeywordsRayleigh Number Liquid Oxygen Liquid Sphere Supporting Fluid Cryogenic Engineer
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