Flow accelerated corrosion (FAC) is a major pipe wall thinning phenomena in power plant. The management of pipe wall thinning is carried out in pipe elements such as elbow, T-tube, orifice, etc. of piping system in power plants. Wall thinning estimation methods in the management is usually applied with pipe wall thickness measurement in Japan.

In piping system, it is known that several pipe elements that are connected in series generate swirl flow. In Mihama Unit 3 pipe failure accident in 2004, it is pointed out the swirl flow caused by the piping layout might influence thinning rate behind orifice. Therefore the arrangement of pipe elements is considered to affect thinning phenomena seriously. So the behavior of swirl flow is one of the major research items to improve FAC model.

The purpose of this paper is to study the influence of swirl flow on wall thinning phenomena generated by the combination of pipe elements. This study focuses on the conditions and parameters (combination, distance, curvature radius of elbow, etc. of pipe elements) that affect the generation of swirl flow and analyzes the effect of such parameters in mass transfer coefficient and flow field of main-stream of swirl flow behind pipe elements. It is expected that axial velocity of main-stream of swirl flow affects distribution of geometry factor under swirl flow on pipe element.

The results of this study will be reflected to the evaluation of fluid-dynamic factor of FAC and can improve the management of wall thinning.

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