球床反应堆面心立方单元局部流动与传热的数值分析

doi:10.11949/0438-1157.20190622

摘要/Abstract

摘要：

球床反应堆燃料球表面局部热点的存在影响到反应堆的安全，其形成与燃料球尺度的冷却剂局部流动密切相关。为保证计算结果的准确性和物理真实性，采用大涡模拟(LES)方法和全结构网格对面心立方(FCC)单元面接触排列方式的局部流动和传热进行了数值分析。研究分析了非定常流动的特点及其对对流换热的影响。燃料球表面的时均温度分布表明燃料球表面存在稳定的热点或热斑，也发现瞬时温度波动较大，存在明显高于时均值的瞬时热点。

关键词: 固定床, 对流, 面心立方, 大涡模拟, 结构网格, 面接触, 数值分析

Abstract:

The existence of hot spots on the surface of pebbles in pebble reactors affects the safety of the reactor and its formation is closely related to the local flow of coolant at the pebble scale. In order to ensure the accuracy and physical reality of the solution, the large eddy simulation (LES) method and the fully structured grid are applied to conduct the numerical analysis of the local flow and heat transfer of the face-centered cubic (FCC) unit in the area contact arrangement mode. The characteristics of unsteady flow and its effect on convective heat transfer are analyzed. The time-averaged temperature distribution indicates that there are stable hot spots on the surface of pebbles, and it is also found that the instantaneous temperature fluctuation on the surface of pebble is large, and there are also instantaneous hot spots where the temperature is significantly higher than the time-averaged temperature.

Key words: fixed-bed, convection, face-centered cubic, LES, structured grid, area contact, numerical analysis

中图分类号:

TK 11⁺2

姚强, 郭雪岩, 杨帆, 王志远. 球床反应堆面心立方单元局部流动与传热的数值分析[J]. 化工学报, 2019, 70(S2): 161-168.

Qiang YAO, Xueyan GUO, Fan YANG, Zhiyuan WANG. Numerical analysis of local flow and heat transfer of FCC domain in pebble bed reactor[J]. CIESC Journal, 2019, 70(S2): 161-168.

图/表 16

图1 球床堆积方式(a)及接触点处理方式(b)

Fig.1 Pebble bed packing methods (a) and contact modes between pebbles (b)

图2 计算模型

Fig.2 Calculation model

表1 物性参数[14]

Table 1 Physical property parameters[14]

参数	氦气	石墨
密度/(kg/m³)	5.36	1750
动力黏度/(N·s/m²)	3.69e^-5	—
热导率/(W/(m·K))	0.3047	25
比热容/(J/(kg·K))	5441.6	1690

图3 FCC面接触单元网格

Fig.3 FCC cell grid with area contact

图4 网格适用性验证

Fig.4 Grid applicability verification

图5 切片位置

Fig.5 Slice positions

图6 球面中心区域的滞止区与尾流区

Fig.6 Stagnation and wake region of spherical central region

图7 瞬时速度和温度分布

Fig.7 Instantaneous velocity and temperature distributions

图8 时均速度和温度分布

Fig.8 Time-averaged velocity and temperature distributions

图9 切片区域瞬时流线图

Fig.9 Instantaneous streamline charts of section areas

图10 三种面接触位置

Fig.10 Three area contact positions

图11 中心球表面瞬时温度分布及距球面0.5 mm处瞬时速度分布

Fig.11 Instantaneous temperature distributions on surface of central pebble and instantaneous velocity distributions

图12 中心球表面时均温度分布及距球面0.5 mm处时均速度分布

Fig.12 Time-averaged temperature distributions on surface of central pebble and time-averaged velocity distributions at 0.5 mm away from sphere

图13 燃料球外围0.5 mm处流场区域时均速度与时均温度梯度夹角的分布

Fig.13 Time-mean distributions of angle between velocity and temperature gradient in flow field at 0.5 mm away from fuel sphere

图14 取线位置

Fig.14 Positions of extracted lines

图15 线上温度瞬时值和时均值分布

Fig.15 Instantaneous and time-mean temperature distributions on lines

参考文献 16

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