J032021 流体温度変動による配管熱疲労に関する研究 : 熱荷重を評価するための流体と構造の温度変動の高精度なCFD解析手法([J032-02]エネルギープラント安全に向けた構造/熱流体/材料の達成問題(2))

Abstract

Temperature fluctuations generated by the mixing of hot and cold fluids at T-junction, which is widely used in nuclear power and process plants, can cause thermal fatigue failure. The existent evaluation method of thermal fatigue provides insufficient accuracy for the evaluation result, because it was developed based on the limited experimental data and the simplified one-dimensional FEA. CFD/FEA coupling analysis is expected as a useful tool for the more accurate evaluation of thermal fatigue. The present paper aims to verify the accuracy of numerical methods of simulating fluid and structure temperature fluctuations at T-junction for thermal fatigue evaluation. The dynamic Smagorinsky model (DSM) is used for LES sub-grid scale (SGS) turbulence model, and a hybrid scheme (HS) is adopted for the calculation of convective terms in the governing equations. Also, heat transfer between fluid and structure is calculated directly based on thermal conduction by allocating grid points within the thermal boundary sub-layer. The simulation results show that the distribution of fluid temperature fluctuation intensity and the range of solid temperature fluctuation are close to the experimental results. Moreover, the peak frequencies of PSD of both fluid and solid temperature fluctuations also agree with the experimental results well. As a result, it has been proven that the numerical methods used in the present paper are of high accuracy.