Countercurrent Flow Limitation in Slightly Inclined Pipes With Elbows

Abstract

Onedimensional (1D) sensitivity computations were carried out for air–water countercurrent flows in a 1/15scale model of the hot leg and a 1/10scale model of the pressurizer surge line in a pressurized water reactor (PWR) to generalize the prediction method for countercurrent flow limitation (CCFL) characteristics in slightly inclined pipes with elbows. In the 1D model, the wall friction coefficient fwG of singlephase gas flows was used. The interfacial drag coefficient of fi=0.03, an appropriate adjustment factor of NwL=6 for the wall friction coefficient fwL of singlephase liquid flows (NwG=1 for fwG of singlephase gas flows), and an appropriate adjustment factor of Nde=6 for the pressure loss coefficient خ¶e of elbows in singlephase flows were determined to give good agreement between the computed and measured CCFL characteristics. The adjusted factors were used to compute and then discuss effects of the inclination angle and diameter on CCFL characteristics.