Geometry factor obtained from wall heat transfer coefficient in high Reynolds number elbow flow

Abstract

Flow accelerated corrosion (FAC) is one of the causes for wall thinning mechanisms in carbon steel pipes. Prediction of geometry factor is the key elements for estimation of FAC. Geometry factor is defined as the ratio of wall mass transfer coefficient in the piping systems such as elbow to that in a straight pipe. In this study, geometry factor of the elbow pipe is computed by using large eddy simulation (LES) for Re=45000, 180000 and 540000. Mass transfer coefficient is evaluated based on the calculations simulating the heat transfer phenomena, instead of the mass transfer. Geometry factors obtained from the heat transfer coefficient by LES are good agreement with experimentally measured values by electrochemical method at Re=45000. Geometry factors on the outer side of the elbow are affected by strong shear flow and decrease with increase of Re. Geometry factors on inner side become large due to the unsteady swirling flow and they slightly depend on Re. The maximum of geometry factors are found on inner side near elbow outlet and their values are 2.38, 2.04, 1.76 for Re=45000, 180000, 540000, respectively.