Leidenfrost Point
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 vapor. 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,
where the properties are evaluated at saturation temperature. Zuber's constant, C is approximately 0.09 for most fluids at moderate pressures.
Read more about this topic: Leidenfrost Effect
Famous quotes containing the word point:
“The great passion in a man’s life may not be for women or men or wealth or toys or fame, or even for his children, but for his masculinity, and at any point in his life he may be tempted to throw over the things for which he regularly lays down his life for the sake of that masculinity. He may keep this passion secret from women, and he may even deny it to himself, but the other boys know it about themselves and the wiser ones know it about the rest of us as well.”
—Frank Pittman (20th century)