KURENAI : Kyoto University Research Information Repository

-4 *3 0.5p ()_1.0
Efg(h,jg) = 7.13 x 10 jgNug pexp (-0.205(h/DH)) (114)
and kd = 0.051 jg.
The deposition coefficient calculated from Eqs. (113) and (114) gives
higher values of kd than those observed in normal annular dispersed flow
[75]. It is considered that droplets entrained from a bubbling or boiling
pool have higher random velocity in the lateral direction when they are
entrained. The deposition coefficient should increase due to this initial
random momentum in the lateral direction. This situation is similar to
the case where droplets are injected from a nozzle [76] into a pipe. In
the latter case, the very high deposition rate near the injection nozzle
is well known [2,5,76].
Comparing Eqs. (96) and (114) the height above the pool surface at
which the momentum controlled region changes fo rdeposition controlled
regime is given by
* *3 0.33
h_ exp (-0.068(h /DH)) = 1.97 x 10 N *0.42Cia)0.23
ugD. (115)
When the droplet deposition is small, Eq. (115) can be approximated by
h*= 1.97 x 103N0.33D*0.42 ()o.23(116)
pg H op
V. 10 ENTRAINMENT AMOUNT NEAR SURFACE REGION
In the near surface region, entrainment consists of all the entrained
droplets from the pool surface. It is given by Eq. (93) , which should be
rewritten as follows in view of Eq. (106).
Efg(h,jg) = 2.48 x 10Cmjgp(117)
-41 .5*1.5-3n4/2P-1.0
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