Editing Leidenfrost effect (section)

== Leidenfrost temperature and surface tension effects ==

The Leidenfrost temperature is the property of a given set of solid–liquid pair. The temperature of the solid surface beyond which the liquid undergoes the Leidenfrost phenomenon is termed the Leidenfrost temperature. Calculation of the Leidenfrost temperature involves the calculation of the minimum film boiling temperature of a fluid. Berenson<ref>{{cite journal |last1=Berenson |first1=P. J. |title=Film-Boiling Heat Transfer From a Horizontal Surface |journal=Journal of Heat Transfer |date=1 August 1961 |volume=83 |issue=3 |pages=351–356 |doi=10.1115/1.3682280 }}</ref> obtained a relation for the minimum film boiling temperature from minimum heat flux arguments. While the equation for the minimum film boiling temperature, which can be found in the reference above, is quite complex, the features of it can be understood from a physical perspective. One critical parameter to consider is the [[surface tension]]. The proportional relationship between the minimum film boiling temperature and surface tension is to be expected, since fluids with higher surface tension need higher quantities of heat flux for the onset of [[nucleate boiling]]. Since film boiling occurs after nucleate boiling, the minimum temperature for film boiling should have a proportional dependence on the surface tension.

Henry developed a model for Leidenfrost phenomenon which includes transient wetting and microlayer evaporation.<ref>{{cite journal |last1=Henry |first1=R.E. |title=Correlation for the minimum wall superheat in film boiling |journal=Transactions of the American Nuclear Society |date=1972 |volume=15 |issue=1 |pages=420–421 |oclc=4434452303 |osti=4694181 }}</ref> Since the Leidenfrost phenomenon is a special case of film boiling, the Leidenfrost temperature is related to the minimum film boiling temperature via a relation which factors in the properties of the solid being used. While the Leidenfrost temperature is not directly related to the surface tension of the fluid, it is indirectly dependent on it through the film boiling temperature. For fluids with similar thermophysical properties, the one with higher surface tension usually has a higher Leidenfrost temperature. A related phenomenon was observed during the solidification of paraffin wax droplets, which develop a characteristic apple-like shape with a central dimple due to the combined effects of gravity, viscosity increase, and heat conduction through a mushy zone.<ref>Roy, P.K., Shoval, S., Shvalb, N., Dombrovsky, L.A., Gendelman, O., & Bormashenko, E. (2023). "Apple-like Shape of Freezing Paraffin Wax Droplets and Its Origin". ''Materials'', 16(16), 5514. [https://doi.org/10.3390/ma16165514]</ref>


For example, for a saturated water–copper interface, the Leidenfrost temperature is {{convert|257|C}}. The Leidenfrost temperatures for glycerol and common alcohols are significantly smaller because of their lower surface tension values (density and [[viscosity]] differences are also contributing factors.)