Research on the Key Influencing Factors of the Backflow Phenomenon on the Primary Side of the Inverted U-tube Steam Generator under Natural Circulation
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摘要: 倒U型管蒸汽发生器（UTSG）在自然循环条件下存在倒流现象，影响一回路冷却剂系统载热能力及自然循环能力。本文参照芬兰压水堆热工实验装置（PWR PACTEL）中UTSG设计参数，利用计算流体力学（CFD）软件Fluent模拟流量匀速下降工况下UTSG中的倒流现象，研究一次侧运行参数、UTSG设计参数以及二次侧运行参数对于倒流现象的影响。结果表明，提高UTSG一次侧温度、一次侧运行压力、倒U型管热导率将增大UTSG的临界质量流量，使得UTSG更易发生倒流；提高UTSG二次侧给水量、二次侧温度以及倒U型管内壁粗糙度将使得UTSG临界质量流量下降，抑制倒流现象发生；而倒U型管壁厚对倒流现象几乎无影响；相较于改变二回路温度，改变一回路温度对于倒流现象的影响更为显著。本研究结果可为UTSG的参数优化提供一定参考。
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关键词:
- 自然循环 /
- 倒U型管蒸汽发生器（UTSG） /
- 倒流 /
- 计算流体力学 /
- 关键影响因素
Abstract: Backflow exists in the inverted U-tube steam generator (UTSG) under the condition of natural circulation, which affects the heat carrying capacity and natural circulation capacity of the primary circuit coolant system. Referring to the design parameters of UTSG in PWR thermal experimental device (PWR PACTEL) in Finland, this paper uses computational fluid dynamics (CFD) software Fluent to simulate the backflow in UTSG under the condition of uniform flow decline, and studies the influence of primary side operation parameters, UTSG design parameters and secondary side operation parameters on the backflow. The results show that increasing the primary side temperature, primary side operating pressure and thermal conductivity of the inverted U-tube will increase the critical mass flow rate of the UTSG, making the UTSG more prone to backflow; Increasing the water supply and temperature on the secondary side of UTSG and the roughness of the inner wall of inverted U-tube will decrease the critical mass flow rate of UTSG and restrain the occurrence of backflow. Changing the wall thickness of inverted U-tube has little effect on the backflow; Compared with changing the temperature of the secondary circuit, changing the temperature of the primary circuit has a more significant impact on the backflow. The results of this study can provide some reference for the parameter optimization of UTSG.-
Key words:
- Natural circulation /
- UTSG /
- Backflow /
- Computational fluid dynamics /
- Key influencing factors
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图 1 PWR PACTEL所配备的 UTSG及其管束分布示意图
Figure 1. Schematic Diagram of UTSG and Its Bundle Distribution Equipped by PWR PACTEL
图 2 三维UTSG模型及倒U型管编号示意图
Figure 2. Schematic Diagram of 3D UTSG Model and Inverted U-tube Numbering
图 3 一次侧入口总质量流量随时间变化示意图
Figure 3. Schematic Diagram of Total Mass Flow at Primary Side Inlet Changing with Time
图 4 1号管质量流量及出口平均温度随网格数量变化图
Figure 4. Variation in the Mass Flow Rate and Outlet Temperature of Tube No. 1 as a Function of the Number of Grids
图 5 UTSG一次侧入口温度对临界质量流量影响
Figure 5. Effect of Primary Side Inlet Temperature of UTSG on Critical Mass Flow
图 6 一次侧运行压力对临界质量流量的影响
Figure 6. Effect of Primary Side Operating Pressure on Critical Mass Flow
图 7 倒U型管壁厚对临界质量流量的影响
Figure 7. Effect of Inverted U-Tube Wall Thickness on Critical Mass Flow
图 8 倒U型管内壁粗糙度对临界质量流量的影响
Figure 8. Effect of Inverted U-Tube Inner Wall Roughness on Critical Mass Flow
图 9 倒U型管壁面热导率对临界质量流量的影响
Figure 9. Effect of Thermal Conductivity of Inverted U-Tube Wall on Critical Mass Flow
图 10 UTSG二次侧给水温度对临界质量流量的影响
Figure 10. Effect of UTSG Secondary Side Feed Water Temperature on Critical Mass Flow
图 11 UTSG二次侧给水量对临界质量流量的影响
Figure 11. Effect of UTSG Secondary Side Water Supply on Critical Mass Flow
表 1 倒U型管设计参数
Table 1. Design Parameters of Inverted U-tube
管编号 对应图1b中的编号 类型 管高/mm 管长/mm 1、2、
3、415、16、17、18 短管 3226 6518 5、6、7 34、35、36 中管 3391 6893 8、9 48、49 长管 3676 7511 
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表 2 一次侧冷却剂物性参数
Table 2. Physical Parameters of Primary Side Coolant
参数 函数关系式 密度（ρ）/(kg·m−3) $\rho = - 2.562 \times {10^{ - 5}}{x^3} + 0.03507{x^2} - 17.19x + 3866$ 定压比热容（cp）/[J·(kg·K)−1] ${c_p} = 9.226 \times {10^{ - 4}}{x^3} - 1.34{x^2} + 655x - 1.032 \times {10^5}$ 导热系数（μ）/[W·(m·K)−1] $\mu = - 8.132 \times {10^{ - 9}}{x^3} + 7.734 \times {10^{ - 6}}{x^2} - 2.533 \times {10^{ - 3}}x + 0.9933$ 动力粘度（$\nu $）/[kg·(m·s)−1] $\nu = - 1.226 \times {10^{ - 11}}{x^3} + 2.062 \times {10^{ - 8}}{x^2} - 1.198 \times {10^{ - 5}}x + 2.487 \times {10^{ - 3}}$ x—温度，K
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表 3 二次侧冷却剂物性参数
Table 3. Physical Parameters of Secondary Side Coolant
参数 函数关系式 ρ/(kg·m−3) $\rho = - 4.829 \times {10^{ - 7}}{x^3} - 1.871 \times {10^3}{x^2} + 0.9018x + 908.3$ cp/[J·(kg·K)−1] ${c_p} = 7.682 \times {10^{ - 5}}{x^3} - 0.075{x^2} + 24.81x + 1416$ μ/[W·(m·K)−1] $\mu = 7.973 \times {10^{ - 9}}{x^3} - 1.552 \times {10^{ - 5}}{x^2} + 8.654 \times {10^{ - 3}}x - 0.804$ $\nu $/[kg·(m·s)−1] $\nu = - 1.938 \times {10^{ - 10}}{x^3} + 2.619 \times {10^{ - 7}}{x^2} - 1.182 \times {10^{ - 4}}x + 0.018$
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