Comparison of air/water and steam/water flooding experiments in a model of the hot leg of a pressurised water reactor

In order to investigate the two-phase flow behaviour in a complex reactor-typical geometry and to supply suitable data for CFD code validation, a model of the hot leg of a pressurised water reactor (PWR) was built at Forschungszentrum Dresden-Rossendorf (FZD). Counter-current flow limitation (CCFL) experiments were performed with air and water at room temperature and pressures up to 3.0 bar as well as with steam and water at pressures up to 50 bar and the corresponding saturation temperature of 264°C.

One selected 50 bar experiment is presented, analysed and high-speed camera images are shown. Furthermore, the flooding curves obtained from the different experimental runs are presented in terms of the Wallis parameter and Kutateladze number, which are commonly used in the literature. However, both parameters fail to correlate properly the data: a discrepancy is observed between the air/water and steam/water series. Therefore, a modified Wallis parameter is proposed, which takes into account the effect of the fluid viscosities on the CCFL.