Critical heat flux densities are used to calculate transition from nucleate boiling to full film boiling and back from film boiling to transient nucleate boiling. To do such calculations (transition from film boiling to nucleate boiling), many authors use Leidenfrost point. Is there a correlation between them or is it the same?
Transition temperature from film boiling to nucleate boiling Ttr is calculated from the equation: qcr2 =h(Ttr - Ts). Here qcr2 is the second critical heat flux density; h is heat transfer coefficient during film boiling; Ts is saturation temperature. The value qcr2 depends on the temperature of a liquid and is directly proportional to Ts - Tm, where Tm is temperature of a liquid. The Leidenfrost temperature doesn't take into account Ts - Tm. Between them could be a correlation. If somebody established such correlation and used for calculations, please, let us know,
Please note that the ratio qcr2/qcr1 = 0.2. Where qcr1 is the first critical heatb flux density; qcr2 is the second critical heat flux density. This ratio was supported by many experiments and is provided by many handbooks. Tolubinsky came to conclusion that during very rapid transient boiling processes, the ratio can be qcr2/qcr1 = 0.05.
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