Prediction Accuracy of One-dimensional Computation for Countercurrent Flow Limitation in Horizontal Pipes

Abstract

Countercurrent flow limitation (CCFL) may occur in a hot leg (consisting of an inclined pipe, a vertical 50-deg elbow, and a horizontal pipe) and a pressurizer surge line (consisting of a vertical pipe, a vertical 90-deg elbow, and a slightly inclined pipe with elbows) under postulated accident conditions in a pressurized water reactor (PWR). In our previous study, we developed a one-dimensional (1D) computation method to predict CCFL characteristics in an inclined pipe with elbows, to generalize the prediction method for CCFL in piping systems. In this study, we did 1D computations for CCFL experiments in horizontal pipes (diameters of D = 0.03-0.65 m and ratios of the length to the diameter of L/D = 4.5-63) to evaluate prediction accuracy of the 1D computation method. The differences of the CCFL constant C (value of J_G^*1/2 at J_L^*1/2 = 0 where J_G^* and J_L^* are the Wallis parameters) between measured and computed values were within dC = ±0.055 for C = 0.4-0.7.