Analysis of Steady-State Flow in downcomer by CFX code

• Main Authors: Chang, Yao-chung, 張耀中
• Other Authors: Chun-kuan Shih
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/09317973615769816568

碩士 === 國立清華大學 === 工程與系統科學系 === 86 === This thesis emphasizes on the understanding of the mathematical models of single-phase flow and multiphase flow in CFX code. The purpose of such studyis to provide the potential users on how to properly setup their CFX modelsfor their particular problems. At the meantime, we also investigated steady state fluid dynamics inside the downcomer of NPP#1 and #2 at the very early stages following postulated recirculation line break accidents. Comparing with the similar studies with PHOENICS, we found CFX results show the same trends but with less conservative predictions. We have also tried to calculate the normal forces exerted on the core shroud from the pressure distributions. We found that special attentions should be paid to those welds near the height where the recirculation pipe is located, especially for the welds in NPP#2. For two-phase flow model in CFX, we noticed that so long as we choose options to include interphase heat transfer, the heat transfer results are identical for cases with homogeneous or multifluid options. If it is chosen that energy is added to both phases,the code will ignore the interphase energy transfer. The interphase mass transfer model provided in the current version of CFX is not complete enough to accommodate the effect of energy transfer and fluid properties. However, we still managed to carry out some sensitivity analysis to understand the procedures in setting up CFX two-phase flow models.