环管内超临界水流动传热实验研究及数值计算-核能科学与工程专业论文.docxVIP

上海交通大学硕士学位论文 万方数据 环形通道内超临界水流动传热实验研究及数值计算 摘 要 超临界水冷堆相比于传统压水堆具有热效率高、系统简化等诸多 特点，但是在设计上还存在许多关键问题有待验证[1]。由于水在拟临 界区域物性急剧变化，使得其流动传热特点的研究存在很多困难，尤 其定位格架附近传热规律的研究更加具有挑战，目前尚未形成统一的 理论来解释超临界水的流动传热现象。本文基于上海交通大学超临界 水回路中进行的环管传热试验，结合CFD数值计算结果，综合分析了 环管中超临界水的流动传热特点。 超临界水在环形通道中的流动传热试验表明，热流密度对流动传 热有很大影响，壁面热流密度越高，对流换热系数越低；定位格架形 状对其下游对流换热系数的衰减规律有很大影响，而且在不同压力条 件下，这种衰减规律的表现形式不同；在诸多传统流动传热关系式中， Bishop公式能更好的预测超临界水在环管中流动时的对流换热系数。 数值模拟结果表明，热流密度通过改变加热棒壁面附近流体的物性参 数来影响对流传热，当热流密度增加时，主流区域湍流强度的降低与 壁面附近流体导热系数的下降是流动传热系数下降的主要原因；CFD 方法由于不能准确计算定位格架下游流体物性参数与流动参数，因而 不能预测对流传热系数的衰减规律；与环管相比，棒束中由于各个子 iii  通道之中流体质量流率与温度分布不均匀,截面上流体之间存在很大 的交混作用，使其流动传热现象有很大不同，重点表现在各个加热棒 周向不同位置对流传热系数的不同。 关键词：超临界水，环管，流动传热，实验研究，数值模拟 iv  AN EXPERIMENTAL AND NUMERICAL STUDY ON HEAT TRANSFER TO SUPERCRITICAL WATER FLOWING IN AN ANNULAR CHANNEL ABSTRACT Compared to traditional PWR, supercritical water cooled reactor (SCWR) has advantages like higher thermal efficiency and a more simplified system. However, there are still many technical problems when it comes to the reactor design. It is very difficult to explore the characteristics of flow and heat transfer due to a drastic variation in physical properties around pseudo-critical point, especially near the region where spacer grid exists. So far, a widely acknowledged theory on the heat transfer to supercritical water has not been achieved. In this thesis, heat transfer experiments of supercritical water flowing in an annular channel on SWAMUP loop in SJTU have been performed and CFD simulations have been applied to analyze the flow and heat transfer characteristics of supercritical water. The experimental results suggest that the wall heat flux has a significant influence on the heat transfer. The heat transfer coefficient decreases with the increase of the wall heat flux. Furthermore, the geometry of spacer grid has a great effect on the decay of grid-enhanced heat transfer in downstream locations. The heat transfer decays in various patterns of manifestation under different pressure c