Editing Leidenfrost effect (section)

== Leidenfrost point ==
[[File:Water droplet Leidenfrost effect cropped.JPG|thumb|A water droplet experiencing Leidenfrost effect on a hot stove plate]]

The Leidenfrost point signifies the onset of stable film boiling. It represents the point on the boiling curve where the heat flux is at the minimum and the surface is completely covered by a vapor blanket. Heat transfer from the surface to the liquid occurs by conduction and radiation through the vapour. In 1756, Leidenfrost observed that water droplets supported by the vapor film slowly evaporate as they move about on the hot surface. As the surface temperature is increased, radiation through the vapor film becomes more significant and the heat flux increases with increasing excess temperature.

The minimum heat flux for a large horizontal plate can be derived from Zuber's equation,<ref name="ReferenceA"/>

<math display="block">{{\frac{q}{A}}_{min}}=C{{h}_{fg}}{{\rho }_{v}}{{\left[ \frac{\sigma g\left( {{\rho }_{L}}-{{\rho }_{v}} \right)}{{{\left( {{\rho }_{L}}+{{\rho }_{v}} \right)}^{2}}} \right]}^{{}^{1}\!\!\diagup\!\!{}_{4}\;}}</math>

where the properties are evaluated at saturation temperature. Zuber's constant, <math>C</math>, is approximately 0.09 for most fluids at moderate pressures.