Analysis of Multi-branch Natural Circulation Characteristics of Passive Residual Heat Removal System in NHR200-Ⅱ Reactor
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摘要: 多支路自然循环系统会出现流量分配不均的现象，为进一步分析系统流动特性，依托低温堆非能动余热排出系统（PRHR）试验台架，建立了多支路并行流道自然循环回路的简化数学模型，利用压降-流量特性图分析了支路倒流现象的机理，并讨论了多种因素对倒流支路数目的影响。分析结果表明：倒流现象降低了PRHR载热功率；增大主换热器（PHE）与空气冷却器（RHE）间的提升高差可以抑制PHE支路倒流现象；存在一临界提升高差，当提升高差小于临界提升高差时，改变PHE或RHE支路的阻力不会改变倒流PHE支路数量，当提升高差大于临界提升高差时，增加PHE支路阻力或减小RHE支路阻力均可以减少倒流支路数量直至完全抑制倒流。
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关键词:
- 并行流道 /
- 自然循环 /
- 非能动余热排出系统（PRHR） /
- 倒流
Abstract: There is uneven flow distribution in multi-branch natural circulation system. In order to further analyze the flow characteristics of the system, a simplified mathematical model of multi-branch parallel-channel natural circulation loop was established based on the passive residual heat removal system (PRHR) system of the NHR200-Ⅱ reactor test facility. The mechanism of the reverse flow phenomenon was analyzed by utilizing the pressure drop-flow rate diagram, and the effects of various factors on the number of reverse flow branches were discussed. The analysis results show that the thermal power of PRHR system is deteriorated as the reverse flow occurred, and increasing the elevation between the primary heat exchanger (PHE) and the air cooler (RHE) can suppress the reverse flow in the PHE branches. There is a critical elevation. When the elevation is less than the critical value, changing the resistance of PHE or RHE branches will not change the number of reverse flow PHE branches. When the elevation is greater than the critical value, increasing the resistance of PHE branches or decreasing the resistance of RHE branches can reduce the number of reverse flow branches until the reverse flow is completely suppressed. -
图 1 NHR200-Ⅱ PRHR系统示意图
1—反应堆压力容器；2—堆芯；3—PHE；4—冷环管；5—热环管；6—稳压器；7—RHE；8—空冷塔侧
Figure 1. Schematic Diagram of PRHR System of NHR200-Ⅱ
图 2 低温堆PRHR的PHE支路简图
s1a—0~1段的长度，其他同理；h1a—1~2段的高度，其他同理；TPHE—PHE温度
Figure 2. Schematic Diagram of PHE Branches of PRHR System in Low Temperature Reactor
图 3 低温堆PRHR系统RHE支路简图
s1b—0~1段的长度，其他同理；h1b—0~1段的高度，其他同理；TRHE—RHE温度
Figure 3. Schematic Diagram of RHE Branch of PRHR System in Low Temperature Reactor
图 4 低温堆PRHR系统不同倒流支路数目对应的压降-流量曲线
Figure 4. Pressure Drop - Flow Rate Curves of PRHR System in Low Temperature Reactor with Different Number of Reverse Flow Branches
图 5 倒流支路对PRHR系统载热功率的影响
Figure 5. Influence of Reverse Flow Branch on Thermal Power of PRHR System
图 7 RHE支路阻力的影响（ $ h < {h_{\text{c}}} $）
Figure 7. Influence of Resistance of RHE Branch
图 8 RHE支路阻力的影响（ $ h > {h_{\text{c}}} $）
Figure 8. Influence of Resistance of RHE Branch
图 9 hc随PRHR系统温差的变化曲线
Figure 9. Variation of hc with Temperature Difference of PRHR System
图 11 不同PHE支路阻力下的PRHR系统工况点（ $ h < {h_{\text{c}}} $）
Figure 11. Operating Point of PRHR System under Different Resistance of PHE Branches
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