Abstract
In the previous study, flow patterns under countercurrent air-water flow were observed in a rectangular channel simulating a PWR (pressurized water reactor) hot leg and close interrelations between flow patterns and countercurrent flow limitation (CCFL) were indicated. In this study, simple calculations of CCFL characteristics based on a momentum equation and numerical simulations using the thermal hydraulic calculation code FLUENT6.3.26 were conducted. The CCFL characteristics by the simple calculations agreed with the measured results but the constant m in the Wallis correlation was underestimated in the region of large air flow rates. In the numerical calculations, flow patterns in the simulated hot leg were not reproduced by 2D calculations due to the limitation of capability to predict the flow pattern transition from stratified flow to wavy-mist flow but were successfully reproduced by 3D calculations because of the interrelation between CCFL characteristics at the inlet and outlet of the simulated hot leg. Falling water flow rates predicted by 3D calculations agreed with the data in the region of large air flow rates.
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