Effect of Variable Angular Piping Bends Geometry on Turbulent Flow of Supercritical Water in an SCWR Plant Piping Network: A Three-Dimensional Computational Fluid Dynamics Investigation

Abstract One of the most critical components of super critical water reactor (SCWR) plant is pipe bend, carrying massive volume of supercritical water. Because of its intense fluctuation of velocity and pressure, it can exhibit unusual flow pattern in pipe bends conveying fluid. This unusual flow pattern may destroy the integrity of the piping network. Alternatively, because of unique chemical and physical properties, transportation of SCW can adversely effect on the integrity of the pipe bends, indicating probable failure of piping network. Therefore, intensive studies of SCW flow in bends are a must as a part of designing an efficient plant piping network. This article presents CFD analysis, carried out to examine the effect of variable pipe bend angle (90 deg, 120 deg, and 135 deg) on turbulent flow of SCW. The analysis indicates that the portion of the straight inlet pipe with fully developed flow shows no variation of results in all bend configurations. The study also reveals that secondary currents strengthen at lower bend angles and culminate the formation of vertices at the outlet of the right-angled elbow. It is found from the study that a greater part of the cross-sectional area is covered by the vortices at the bend midplanes compared to the bend outlets, where mixing of stream wise flow occurs as well. It is revealed that the radial positions of each vortex center are closer to the circumference of the pipe, and appear to be insensitive to bend angle. The study is ended with the comparison between supercritical water and normal water at standard conditions.