Abstract
We have previously done numerical simulations using the two-fluid model implemented in the CFD software FLUENT6.3.26 to investigate effects of shape of a flow channel and its size on CCFL (countercurrent flow limitation) characteristics in PWR hot leg models. We confirmed that CCFL characteristics in the hot leg could be well correlated with the Wallis parameters in the diameter range of0.05 m≤D≤0.75 m. In the present study, we did numerical simulations using the two-fluid model for the air-water tests withD=0.0254 m to determine why CCFL characteristics forD=0.0254 m were severer compared with those in the range,0.05 m≤D≤0.75 m. The predicted CCFL characteristics agreed with the data forD=0.0254 m and indicated that the CCFL difference betweenD=0.0254 m and0.05 mm≤D≤0.75 mm was caused by the size effect and not by other factors.
Highlights
Reflux condensation by steam generators (SGs) is considered as one of the possible core cooling methods under hypothetical accident conditions in pressurized water reactors (PWRs)
The core cooling performance heavily depends on the occurrence of countercurrent flow limitation (CCFL) in the hot leg which consists of a horizontal pipe, an elbow, and an inclined pipe
In order to investigate effects of shape of a flow channel and its size on CCFL characteristics in hot leg models, we have previously done numerical simulations using a two-fluid model implemented in the CFD software
Summary
Reflux condensation by steam generators (SGs) is considered as one of the possible core cooling methods under hypothetical accident conditions in pressurized water reactors (PWRs). To compare CCFL characteristics in hot leg models, Vallee et al [3] selected three geometrical factors: the horizontal pipe length to diameter ratio (LH /D), the inclined pipe length to diameter ratio (LI /D), and the elbow angle θ. They showed that even for similar geometrical factors, there was clear deviation between CCFL characteristics due to size effects. In order to investigate effects of shape of a flow channel and its size on CCFL characteristics in hot leg models, we have previously done numerical simulations using a two-fluid model implemented in the CFD software
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