Development and Validation of Multi-zone Non-equilibrium Steam-gas Pressurizer Model
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摘要:
先进一体化小堆采用蒸汽-氮气稳压器，其结构简单，具有很好的自稳压能力。为了研究蒸汽-氮气稳压器的热工水力特性，建立了基于多区非平衡状态的蒸汽-氮气稳压器模型。该模型由液区、饱和区和气区3部分组成，每个区进一步均分为多个控制体。本研究从质量和能量守恒角度描述了稳压器中的重要热工水力学现象：体积蒸发、体积冷凝以及壁面换热等，并提出了控制方程的离散求解方法。通过稳压器升压实验结果对蒸汽-氮气稳压器模型进行了验证，结果表明，在升压阶段，多区非平衡稳压器模型可准确模拟压力响应特性，计算值与实验值相对误差在9%以内；在冷凝降压阶段，由于氮气存在对壁面换热冷凝的影响，导致计算值与实验值误差增大。整体上，多区非平衡稳压器模型能够较好地预测蒸汽-氮气稳压器在瞬态下的压力响应特性，可用于汽-气稳压器稳压特性分析。
Abstract:The advanced integrated small reactor adopts steam-gas pressurizer with simple structure and pressure self-stabilizing ability. In order to study the thermo-hydraulics characteristics of steam-gas pressurizer, a steam-gas pressurizer model based on multi-zone non-equilibrium state was established. The multi-zone non-equilibrium steam-gas pressurizer model consists of three parts: liquid zone, saturated zone and gas (steam) zone, and each zone could be further divided into several control volumes. From the point of view of mass and energy conservation, the important thermodynamic and hydraulic phenomena in pressurizer, such as volume evaporation, volume condensation and wall heat transfer, were described. By assuming that the volume evaporation and condensation come from the rise of bubbles and the fall of condensate, the volume evaporation models and volume condensation models were established, and considering the influence of nitrogen on the heat exchanger process in the gas (steam) zone, the wall heat exchange model was modified by empirical relation to ensure that the heat exchange process could be accurately simulated, furthermore the discrete solution method of the steam-gas pressurizer governing equation was proposed. The calculated values of the steam-gas pressurizer model were compared with the boosting experimental results of the steam-gas pressurizer with different nitrogen fractions (3.2%, 9.7%, 20%) of Massachusetts Institute of Technology (MIT). The results show that, in the boosting stage, the multi-zone non-equilibrium steam-gas pressurizer model can accurately simulate the pressure response characteristics. The maximum relative error between the multi-zone non-equilibrium steam-gas pressurizer model calculated pressure value and the experimental value is about 1.93% under the 9.7% nitrogen fraction case, and about 1.60% under the 3.2% nitrogen fraction case, and 3.80% when the model calculates the pressure value and the experimental value under the 20% nitrogen fraction case. In the condensation and depressurization stage, the relative error between the calculated value and the experimental value increases due to the influence of nitrogen on the heat exchange condensation of the wall, but the relative error between the model calculated value and the experimental value of different nitrogen fraction cases is within 9%. On the whole the developed steam-gas pressurizer model can accurately predict the pressure response of pressurizer and can be used to analyze the pressure stabilization characteristics of steam-gas pressurizer.
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Keywords:
- steam-gas pressurizer ,
- multi-zone non-equilibrium ,
- model development ,
- validation
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图 4 9.7%氮气份额下压力计算值与实验值对比
Figure 4. Pressure comparison between calculated and experimental values of 9.7% nitrogen fraction
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图 5 9.7%氮气份额下不同区域温度对比
Figure 5. Comparison of temperature in different regions of 9.7% nitrogen fraction
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图 6 3.2%和20%下氮气压力计算值与实验值对比
Figure 6. Pressure comparison between calculated and experimental values of 3.2% and 20% nitrogen fractions
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