EXPERIMENTAL INVESTIGATION OF THE REWETTING PROCESS AT PRESSURES OF 1-7 BAR

Several water experiments have been carried out to investigate the physical mechanisms relevant to the rewetting phenomena either at atmospheric conditions or in a steam environment. Yet, there seems to be a scarcity of experimental data for the low pressure range from 2 to 7 bar with parameters the liquid film flowrate and the subcooling. An experimental facility to simulate two-phase low-pressure water flow phenomena has been designed, constructed and employed to investigate the rewetting process of hot surfaces in a water-steam environment at pressures in the above range, as well as at atmospheric conditions; the facility is on-line interfaced to computers which control its operation and undertake all the data acquisition tasks. Furthermore, a numerical method to experimentally evaluate the wet front position along the rod was introduced. The present paper describes the experimental work aimed at studying the wet front propagation along a stainless steel fuel rod, in a top-flooding environment in the pressure range 1-7 bar, wall temperatures up to 550°C and at a liquid flowrate of 10-3m3min-1 at both saturated steam conditions and in atmospheric environment with water subcooling in the range 0-75K. The experimental results fitted well to an existing dimensionless rewetting correlation, together with world available vapour environment rewetting data extending its validity down to the pressure of 1 bar. Furthermore, the effect of the inlet water subcooling was introduced in to this correlation.