Film Boiling
From Thermal-FluidsPedia
When the excess temperature increases beyond the minimum heat flux point, boiling enters the film boiling regime, characterized by a continuous vapor film covering the entire surface. The major thermal resistance is in this vapor layer. Unlike the vapor film in the transition boiling regime, that in the film boiling regime is stable.
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Film Boiling Analysis
Since the liquid is separated from the heating surface by a stable vapor film, heat transfer in this regime can be obtained by analyzing evaporation at the liquid-vapor interface.
See Main Article Film Boiling Analysis
Direct numerical simulation of film boiling
In additional to the above analytical results about film boiling, numerical solutions on this topic were also reported in the recent literature. Esmaeeli and Tryggvason (2004) solved the single-field governing equations using a second- order space-time accurate front-tracking/finite difference method on a staggered grid.
See Main Article Direct numerical simulation of film boiling
Leidenfrost Phenomena
A drop of liquid is introduced to a solid surface of constant temperature. If the temperature of the solid is around the boiling point of the liquid, the drop will rapidly boil and evaporate. However, if the solid is held at a temperature much higher than the boiling point of the liquid, a thin film of vapor forms between the solid and the liquid. A drop that floats on its own vapor in this way is called a Leidenfrost drop, named after the German physician, Johann Gottlob Leidenfrost, who first reported the phenomenon in 1756.
See Main Article Leidenfrost Phenomena.
References
Faghri, A., and Zhang, Y., 2006, Transport Phenomena in Multiphase Systems, Elsevier, Burlington, MA
Faghri, A., Zhang, Y., and Howell, J. R., 2010, Advanced Heat and Mass Transfer, Global Digital Press, Columbia, MO.
Esmaeeli, A., and Tryggvason, G., 2004, “Computations of Film Boiling. Part I: Numerical Method,” International Journal of Heat and Mass Transfer, Vol. 47, pp. 5451-5461.