Numerical calculations on countercurrent gas-liquid flow in a PWR hot leg. (2) Steam-water flow under PWR plant conditions

In order to improve the countercurrent flow model of a transient analysis code, countercurrent air-water tests were previously conducted using a 1/15th scale model of the PWR hot leg at Kobe University. Then numerical calculations were made of the test results using the thermal-hydraulic analysis code FLUENT6.3.26 and an Euler-Euler model. The calculated flow patterns in the hot leg were quite similar to the observed results, and the calculated CCFL (countercurrent flow limitation) characteristics agreed well with the measured data. In the present study, we carried out numerical calculations for steam-water flow under PWR plant conditions. The calculated flow patterns in the hot leg were similar to the observed results in the 1/15th scale air-water tests. Furthermore, the calculated CCFL characteristics correlated with Wallis parameters agreed well with the data by the 1/15th scale air-water tests and the full-scale steam-water UPTF tests. The results indicate that the correlations used for the gas-liquid interfacial friction are valid. (author)