C型换热器管外流体两相自然循环数值模拟
Numerical Simulation of Two-phase Natural Circulation Outside Tube of C-type Tube Heat Exchanger
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摘要: 建立了简化的C型换热器管外流体CFD分析模型，模拟了反应堆安全壳内置换料水箱（IRWST）中典型气液两相自然循环特性。首先用公开发表文献中的试验数据对计算方法进行校验，计算中采用的湍流模型、壁面沸腾模型等能较好地捕捉主流流体升温特性、两相自然循环特性。结果表明：C型换热器增加了管外流体流场分布的不均匀性，提高了冷、热流体间的搅混强度，有助于降低管外流体温度差，增加大容积水池内的自然循环能力；但由于壁面对气泡的阻滞作用，换热器弯管及水平管局部区域空泡份额最大，发生了气泡聚集。计算结果可为非能动余热排出换热器的设计提供支持。Abstract: A CFD analytical model of flow domain outside the tube of heat exchanger with C-type tubes was established to simulate typical two-phase natural circulation characteristics in IRWST of reactor. The analytical model was firstly validated by experimental data in open literature, and proved that the turbulence model and wall boiling model were feasible to describe the heating up process and two-phase flow characteristics. The calculation results show that the natural circulation in large pool is enhanced with C-type tube which increases the flow turbulence by mixing hot and cold water intensively and reduces their temperature difference. Whereas, bubble accumulation and maximum gas volume fraction occur in some areas of elbow and horizontal pipe, because of bubbles blocked by walls. The calculation results can contribute to a better understanding of the processes and give hints for heat exchanger design of the passive residual heat removal system.
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Keywords:
- two-phase ,
- natural circulation ,
- large pool ,
- CFD
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