Numerical Study of the Influence of Rolling Motion on the Spacer Effect of Low Flow Convective Heat Transfer
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摘要: 针对摇摆条件下低流量对流传热格架效应开展了数值研究。基于实验数据对摇摆模型进行了验证，确立了基于SST k-ω湍流模型的计算流体动力学（CFD）方法。结果表明：①对周向平均时均传热，摇摆会增强低流量工况格架下游传热。但在混合对流恶化恢复区和自然对流区，格架效应仍存在阻尼振荡衰减现象，且振荡幅度减小；②对局部时均传热，热点始终位于垂直摇摆轴方向，摇摆弱化该方向传热，且该方向格架导致的传热弱化现象被进一步增强；③对热点位置瞬时传热，计算工况中瞬时传热系数的最大弱化程度较充分发展稳态可达40%，安全分析中需重点关注。Abstract: A numerical study was carried out on the spacer effect of low flow convective heat transfer under rolling motion. The rolling model was verified based on the experimental data, then a model-based computational fluid dynamics (CFD) method was established. The results show that for the circumferential mean time-averaged heat transfer, the heat transfer downstream of the spacer is enhanced under low flow conditions. However, in the mixed convection deterioration recovery area and natural convection area, the spacer effect still has damping oscillation attenuation, and the oscillation amplitude decreases. For local time-averaged heat transfer, the hot spot always lies in the direction of vertical rolling axis, and the heat transfer is weakened in that direction under rolling motion, and the heat transfer weakening caused by the spacer in that direction is further enhanced. For the instantaneous heat transfer at the hot spot, the maximum weakening degree of the instantaneous heat transfer coefficient can reach 40% of the fullt developed steady state, which needs to be paid attention to in safety analysis.
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Key words:
- Rolling motion /
- Spacer effect /
- Exponential attenuation /
- Damping oscillation /
- Heat transfer weakening
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图 3 摇摆模型
ω—摇摆角速度；β—摇摆角加速度；r—流体微元的矢径；g—重力加速度；u—流体微元的速度
Figure 3. Model of Rolling Motion
图 9 周向平均时均传热特性
Nus—光滑圆管内的努塞尔数
Figure 9. Circumferential Average Time-averaged Heat Transfer Characteristics
图 10 Y+方向时均传热特性
Figure 10. Time-averaged Heat Transfer Characteristics at Direction Y+
图 12 Case2瞬时传热特性
Nu0—格架通道内稳态下的努塞尔数
Figure 12. Transient Heat Transfer Characteristics of Case 2
图 13 周向平均瞬时传热特性
Figure 13. Circumferential Average Transient Heat Transfer Characteristics
表 1 几何参数与边界条件设置
Table 1. Geometric Parameter and Boundary Conditions
参数 定义 圆形通道内径(D)/mm 11.9 圆形通道长度(L)/m 3（约252D） 运行压力(p)/MPa 15.5 工作介质 单相水 工质物性参数 NIST Real Gas Model 重力加速度/(m·s−2) −9.81 入口边界条件 质量流入口 出口边界条件 压力出口 壁面边界条件 无滑移、等热流密度 质量流密度/(kg·m−2·s−1) 50~600 热流密度(q)/(kW·m−2) 20~140 入口温度/K 400~500 雷诺数(Re) 4809~32078 
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