| Summary: | Countercurrent flow limitation (CCFL) is an important phenomenon for
numerous engineering applications and safety of light water reactors. In particular,
the possible occurrence of CCFL located in the hot-leg of a Pressurized Water
Reactor (PWR) during LOCA accidents for nuclear safety research. Study into gasliquid
countercurrent two-phase flow in a model of pressurized water reactor
(PWR) hot leg has been carried out over the last several decades. In the present
study, the experimental data of the CCFL for gas-liquid in a horizontal and inclined
pipe are investigated. Thus the observation of two-phase flow characteristics of gasliquid
horizontal pipe and inclined pipe as the basis for investigating the
phenomenon of in-depth counter-flow characteristics by visualization method.
In this study conducted experiments using small scale of the actual PWR hotleg,
the pipe diameter of the circular scale of 1/30th of a German Konvoi PWR,
while the riser angle is 50°. The characteristics of the flow pattern was captured by
a highspeed camera along the hot leg gives the appearance of interface between gas
and liquid. Characteristic is observed from the onset of flooding to zero penetration.
The onset of flooding identified by analyzing the changes of water level in lower
tank.
From the high-speed observations it was found that the initiation of flooding
coincides with the formation of slug flow are formed at the crest of the hydraulic
jump. At low liquid flow rates, slugging appears close to the bend
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