National Technical University of Athens
School of Mechanical Engineering
Nuclear Engineering Department

NURETH-16 International Topical Meeting on Nuclear Reactor Thermal Hydraulics Chicago, IL, USA, August 30 - September 4, 2015

An experimental study on the quench front velocity and temperature during rewetting of a hot vertical rod

N. Lymperea, A. Nikoglou and E.P. Hinis
Nuclear Engineering Department NTUA, 15780 Athens, GREECE
This study presents experimental work upon the rewetting mechanism of bottom flooding of a vertical annular channel enclosing a concentrically heated rod. A one loop experimental rig with two phase water flow was used to simulate the dry out and the rewetting process at atmospheric conditions. Experiments have been conducted for water mass flow-rate within the range of 8.33 g·s -1 to 50.01 g·s -1, inlet water subcooling up to 25°C and initial surface temperature of the rod up to 550°C. Beyond the generic remark that the quench velocity increases with increasing inlet sub-cooling, increasing liquid mass flow-rate and decreasing initial wall temperature an investigation is conducted on the effect of the geometry of the annulus upon the quench velocity and the rewetting mechanisms by comparing the present data with data from previous experimental works. The comparison is carried out by employing the thermal properties and the geometrical characteristics of the rod via the dimensionless Peclet number and a modified Biot number. In addition, the effect of the experimental conditions on the quench temperature is examined and contrasted to previous top rewetting experiments. An empirical correlation for the prediction of the quench temperature with respect to the physical properties of the heated surface along with the experimental conditions is introduced.