TOPFLOW experiments on counter-current flow limitation in a model of the hot leg of a PWR


TOPFLOW experiments on counter-current flow limitation in a model of the hot leg of a PWR

Vallee, C.; Seidel, T.; Lucas, D.; Beyer, M.; Prasser, H.-M.

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 was built at Forschungszentrum Dresden-Rossendorf (FZD). The hot leg model is devoted to optical measurement techniques, therefore, a flat test section design was chosen and equipped with large windows. In order to enable the operation at high pressures, the test section is installed in the pressure chamber of the TOPFLOW test facility of FZD, which is used to perform the experiments under pressure equilibrium with the inside atmosphere. Counter-current flow limitation (CCFL) experiments were performed, simulating the reflux-condenser cooling mode appearing in some small break LOCA scenarios. The fluids used were air and water at room temperature and pressures of up to 3.0 bar, as well as steam and water at pressures of up to 50 bar and the corresponding saturation temperature of 264°C. One selected 50 bar experiment is presented in detail and the flow behaviour observed with the high-speed camera is analysed.

Furthermore, the flooding characteristics 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 properly correlate 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. Finally, the new parameter was validated successfully against the UPTF data. This shows that the proposed modification of the Wallis parameter allows a significant improvement for experimental series with variation of the viscosities.

Keywords: two-phase flow; flooding; counter-current flow limitation; hot leg; pressurised water reactor; Wallis parameter; viscosity

  • Lecture (Conference)
    NURISP open General Seminar, 30.11.-01.12.2009, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-13459
Publ.-Id: 13459