Evaluation of Mass Transfer Coefficient Under Swirl Flow Generated by the Combination of Pipe Elements

Flow accelerated corrosion (FAC) is the major pipe wall thinning phenomena in power plants. The management of pipe wall thinning has been carried out for pipe elements such as elbow, orifice, etc. of the piping system in power plants. It is usually applied to thinning estimation methods with a combination of analytical code and measurement of pipe wall thinning. In piping system, it is known that several pipe elements which are connected in series may generate swirl flow. Therefore the arrangement of pipe elements is considered to be one of the major reasons to affect thinning phenomena. In Mihama Unit3 pipe failure accident of 2004, it was pointed out the swirl flow caused by piping layout might influence thinning rate after orifice. This paper focuses on the conditions and parameters (combination, distance, etc. of pipe elements) that affect the generation of swirl flow and analyzes the effect of such parameters in mass transfer coefficient after the pipe elements. The results of this research can be utilized for taking account for the effect of swirl flow in the calculation of geometry factor to improve the accuracy of simulation codes.