Numerical simulation of heat transfer test of forced convection supercritical water in a circular pipe

The Supercritical-Water-Cooled Reactor (SCWR) is a high-temperature, high-pressure water cooled reactor that operates above the critical pressure of water. In this study, to perform thermal hydraulic analysis of SCWR, the three-dimensional two-fluid model analysis code ACE-3D, which has been developed in Japan Atomic Energy Agency, was improved to handle the thermal hydraulic properties of water at supercritical region. In this paper, the existing heat transfer experiments of supercritical water flowing in a vertical circular pipe were analyzed with the ACE-3D code to assess the prediction performance of the code. Wall surface temperature was underestimated by the ACE-3D code using standard k-ε model as turbulence model with wall function. Main cause of these underestimations was thought to be the wall function that cannot describe the effects of rapid fluid property variation near the wall. Then the equivalent eddy diffusivity model, which was proposed by Kunugi, was introduced to the ACE-3D code to improve evaluation of turbulent heat transfer coefficient vicinity of the wall. As a result, it was confirmed that the calculated wall surface temperature by the modified code agreed well with the measured results. (author)