KURENAI : Kyoto University Research Information Repository

liquid level is very low, i.e., 5-6 mm for Akselrod et al. [62] and 38 mm for
Cheng et al. [28]. Under these conditions, a steady gas jet should form at
the pool interface as observed by Muller et al. [63]. For this case a is
almost independent of jg. Hence--
v. j*3/4 N1/4 0*-1/4 (:)1//2(55)
9f
In Fig. 3, the experimental data of Akselrod et al. [62] and Cheng et al. [28]
* (( 1/4p1/21
are plotted in v. 'jjg*3/4N ug (-)Jvs. 0lane. It can be seen that
the experimental data for the initial velocity of droplets are well correlated
by
1/
vi = 205 j93/4 N1/4 0*-1/4 (:)2g(56)
pgf
For a system with a much higherliquid level, which is of considerable
practical importance, the void fraction is a function of the gas superficial
velocity jg. For this case a correlation between a and jg is necessary. The
void fraction in a liquid pool generally shows lower values than those
predicted by the one-dimensional drift-flux model. This is mainly due to the
recirculation of liquid in the pool. Some empirical correlations for the void
fraction are available [64-67] for this kind of flow.
Margulova [64]'proposed the following dimensional correlation for a steam
water system;
a = (0.576 + 0.00414 P) j9'75,(57)
where P is pressure in atm and jg in m/s. Kurbatov [65] presented a
dimensionless correlation given by
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