In this paper, we have investigated the process of the first stage (film state boiling) of rapid cooling due to quenching of high temperature body. The series of experiments were carried out keeping on the initial conditions of test body constant under the various conditions of cooling media. Arranging the data obtained by the experiment for 22 sorts of liquids used as cooling medium, the authors established an empirical formula shown as follows;
where α stands for heat transmission coefficient in cal/cmcm2sec°C, R the rdius of the specimen in cm, Δu
1=u
R-u
0°C, Δu
2=u
2-u
0°C, u
R surface temperature of a specimen, u
2 boiling temperature of cooling liquids, u
0 temperature of cooling liquids, and λ, σ, γ, c
p, ν and a are the same ones shown in table 1.
From eq. (2) they confirmed the following items.
1) Nusselt's Number αR/λ grows up with the increase of σ and a, whereas it decreases with the increase of γ and ν.
2) Slight variation of σ affeets considerablly Nusselt's Number.
3) The numerator of Δu/Δu
2 becomes a measure of the thickness of vapor film and Nu decreases with the rising of Δu
1 which is increased with the growth of film. The denominator Δu
2 is changed by the variation of u
2 and becomes a measure of influence of boiling temprature.
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