Numerical Analyses to Simulate Thermal Stratification Phenomenon in a Piping System

Abstract

In some portions of nuclear piping systems, stratification phenomena may occur due to the density difference between hot and cold stream. When the temperature difference is large, the stratified flow under diverse operating conditions can produce high thermal stress, which leads to unanticipated piping integrity issues. The objectives of this research are to examine controvertible numerical factors such as model size, grid resolution, turbulent parameters, governing equation, inflow direction and pipe wall. Parametric threedimensional computational fluid dynamics analyses were carried out to quantify effects of these parameters on the accuracy of temperature profiles in a typical nuclear piping with complex geometries. Then, as a key finding, it was recommended to use optimized mesh of real piping with the conjugated heat transfer condition for accurate thermal stratification analyses.

Status of Thermal Stratification Research on Piping System in Korea Nuclear Power Plant

“…1)하였으며 실측 데이터로 열성층 영향을 평가하였다 (12) . 또한 한울 5,6호기를 대상으 로 발전소 가열조건에서 3차원 열유동 해석으로 열 성층 현상의 발생 및 구조건전성을 확인하였으며 (13) , 냉각재 환경이 피로수명에 미치는 영향(환경피로) (14) , 열성층 현상을 정확하게 모사하기 위한 해석인자의 영향 (15) 및 열응력 평가를 위한 해석 모델링(pipe element, shell element, solid element)의 비교 검토가 수행되었다 (16) .…”