基于丝网探针的螺旋管内气液两相流气泡行为研究

doi:10.11949/0438-1157.20220610

摘要/Abstract

摘要：

核反应堆蒸汽发生器的传热面由螺旋管束组成。螺旋管的三维螺旋结构使得泡状流和塞状流等气液两相流中的气泡在重力、离心力和浮力等作用下在管道内部呈现不对称的相分布状态，两相滑移速度增大，显著影响换热性能并导致DNB型传热恶化难以预测。实验介质为空气-水，结合自主开发的电导式丝网探针技术并发展先进的数据后处理算法，实现了复杂流场的三维时空重构和离散气泡粒径的精细测量，获得了螺旋管内泡状流和塞状流的截面空泡分布规律。基于研究结果，可根据气泡分布规律对螺旋管道的几何结构进行调整以避免传热恶化，为螺旋管式蒸发器的安全设计提供了基础数据和优化思路。

关键词: 蒸汽发生器, 螺旋管, 丝网探针, 气液两相流, 气泡, 粒度分布

Abstract:

The heat transfer surface of the nuclear reactor steam generator consists of helical tube bundles. As the spatial spiral structure of the tubes, the slip velocity between phases increases due to the combined effect of gravity, centrifugal force and buoyancy. Accordingly, the distribution of the bubbles in bubbly flow and plug flow shows an asymmetric profile, leading to a significant effect on the heat transfer performance and even the occurrence of departure from nucleate boiling (DNB). In this paper, we employ the developed conductive wire mesh sensor and data post-processing algorithm to investigate the flow field and bubble behaviors in both bubbly and plug flow in a helically coiled tube. Reconstruction of the time and space distribution of the flow field based on the proposed algorithm provides an in-depth knowledge of the characteristics of the bubbles. Based on the present study, the geometric structure of the helically coiled tube can be optimized to avoid heat transfer deterioration, which provides basic experimental data and optimization for the design of the helically coiled tube evaporator. The results indicate that both the increase of the superficial gas velocity and superficial liquid velocity can promote the bubble coalescence. The increase of the gas velocity increases the instability of the gas-liquid interface, and the higher liquid velocity splits the gas plug into several small bubbles in the plug flow.

Key words: steam generator, helically coiled tube, wire mesh sensor, gas-liquid two-phase flow, bubble, particle size distribution

中图分类号:

O 359

戴军涛, 刘莉, 刘帅, 顾汉洋, 王科. 基于丝网探针的螺旋管内气液两相流气泡行为研究[J]. 化工学报, 2022, 73(10): 4377-4388.

Juntao DAI, Li LIU, Shuai LIU, Hanyang GU, Ke WANG. Investigation of bubble behaviors in gas-liquid two-phase flow in helically coiled tube based on wire mesh sensor[J]. CIESC Journal, 2022, 73(10): 4377-4388.

图/表 18

图1 实验系统示意图

Fig.1 Experimental setup

表1 仪表量程和不确定度

Table 1 Range and uncertainty of test instruments

仪表	量程	不确定度
气体转子流量计	10~100 m³/h	±0.15%
气体转子流量计	2.5~25 m³/h	± 0.35%
液体电磁流量计	3.6~36 m³/h	± 0.1%
液体电磁流量计	0~0.64 m³/h	± 0.1%
高速摄像机	0~10000帧/秒	—

图2 可视化螺旋管实验段

Fig.2 Transparent helically coiled tube

图3 丝网探针结构实物图及示意图

Fig.3 The real figure and schematic diagram of wire mesh sensor structure

图4 三维螺旋流型重构典型结果

Fig.4 Typical result of 3D flow pattern reconstruction

图5 邻域结构示意图

Fig.5 Neighborhood structure

图6 气泡识别算法工作流程

Fig.6 Algorithm running process

图7 算法原理展示图

Fig.7 Algorithm principle

图8 算法准确性验证

Fig.8 Algorithm validation

图9 泡状流中气泡分布特征（jg=0.04 m/s）

Fig.9 Bubble distribution in bubbly flow (jg=0.04 m/s)

图10 泡状流三维流型重构（jg=0.04 m/s）

Fig.10 3D reconstruction of bubbly flow (jg=0.04 m/s)

图11 泡状流中气泡等效粒径概率密度函数分布（jg=0.04 m/s）

Fig.11 PDF of bubble equivalent diameter in bubbly flow(jg=0.04 m/s)

图12 高液速塞状流中气泡分布特征（jg=0.08 m/s）

Fig.12 Bubble distribution in high-liquid-velocity plug flow (jg=0.08 m/s)

图13 高液速塞状流三维重构（jg=0.08 m/s）

Fig.13 3D reconstruction of high-liquid-velocity plug flow (jg=0.08 m/s)

图14 高液速塞状流中气泡等效粒径概率密度函数分布（jg=0.08 m/s）

Fig.14 PDF of bubble equivalent diameter in high-liquid-velocity plug flow (jg=0.08 m/s)

图15 低液速塞状流中气泡分布特征（jg=0.08 m/s）

Fig.15 Bubble distribution in low-liquid-velocity plug flow (jg=0.08 m/s)

图16 低液速塞状流三维重构（jg=0.08 m/s）

Fig.16 3D reconstruction of low-liquid-velocity plug flow (jg=0.08 m/s)

图17 低液速塞状流中气泡等效粒径概率密度函数分布（jg=0.08 m/s）

Fig.17 PDF of bubble equivalent diameter in low-liquid-velocity plug flow (jg=0.08 m/s)

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