An experimental study of quenching of a hot vertical tube by sudden introduction of a falling liquid filmwas
investigated under different methods of venting the generated steam. The steam generated during the
quenching process may form a countercurrent vapor velocity which exceeds the onset of flooding limit
causing flooding of the liquid film and resisting the propagation of the quench front delaying the rewetting
process. To study the effect of this steam countercurrent flow, experiments were carried out in three stages.
In the first stage, the tubewas closed from top to force the steam generated to be vented from bottom. In the
second stage, both ends of the tube were opened to allow venting of the steam from both ends. In the third
stage, the tube was closed at bottom and the steam was vented from top. The results showed that, the
rewetting velocity in case of bottom steam-venting is higher than that in case of top and bottom steamventing
which in turn is higher than that in case of top steam-venting. For the three methods of steam
venting, the quenching velocity decreases with increasing the initial tube temperature and the inlet liquid
temperature and decreasing the liquid flow rate. Experimental correlations for rewetting velocities were
deduced from experimental data for different cases of steam venting directions. Predictions of equations
were compared with the present and previous experimental data and good agreement was found.