Void fraction distribution of vapor-water two-phase flow in vertical tube bundles using gamma densitometer

doi:10.11949/j.issn.0438-1157.20181277

Abstract

Abstract:

In the vapor-water two-phase flow between vertical tube bundles of steam generators, void fraction is an important parameter. Gamma ray method was used to measure the void fraction distribution under high temperature and high pressure. The experimental pressures were 5, 7, 9 MPa, respectively，the mass flow was 300 kg/(m²?s), and the thermodynamic vapor quality ranged from 0.003 to 0.4. The distribution of the void fraction in vertical tube bundles was obtained and the effects of thermodynamic vapor quality and volume fraction were investigated. Compared with the classical formula calculation model, in the low-dry zone, the relative error between Miropolskii model, Smith model and Armand model with the experimental data are more than 30%, in areas with high dryness, error is small. Based on Armand model, a practical correlation of average void fraction and volume fraction on the section was calculated by multiple linear regression. It can be concluded that the correlations agree well with Japan Nuclear Power Engineering Corporation (NUPEC) experimental data, the relative error is less than 15%. The results show that a gamma ray method can be used to measure and predict the distribution of the void fraction in vertical tube bundles under high-temperature and high-pressure effectively. In general, it is of great significance to the structural design and flow characteristics of steam generator.

Key words: high-temperature and high-pressure, vertical tube bundle, gas-liquid flow, void fraction, gamma ray

摘要：

在立式蒸汽发生器垂直管束间的气液两相流中，截面含气率是其中一个重要参数。使用γ射线法对高温高压下垂直管束间气液两相流截面含气率的分布规律进行了实验研究。实验压力分别为5、7、9 MPa，质量流速为300 kg/(m²?s)，热力学干度的范围为0.003 ~ 0.4。实验得到了垂直管束间截面含气率随热力学干度、体积含气率和压力的变化关系；并与经典公式的计算结果对比发现，在低干度区域，实验结果与Miropolskii模型、Smith模型和Armand模型偏差较大，均大于30%，在高干度区域偏差较小；基于Armand理论，通过多元线性回归法拟合出本文工况下平均截面含气率的计算关联式，与日本核动力工程公司(NUPEC)的实验数据偏差小于15%。本研究对蒸汽发生器的结构设计和流动特性研究具有重要意义。

关键词: 高温高压, 垂直管束, 气液两相流, 截面含气率, γ射线

CLC Number:

O 359
TK 124

Jie CHENG, Yajun GUO, Teng WANG, Miao GUI, Zhaohui LIU, Zhiqiang SUI. Void fraction distribution of vapor-water two-phase flow in vertical tube bundles using gamma densitometer[J]. CIESC Journal, 2019, 70(4): 1375-1382.

程洁, 郭亚军, 王腾, 桂淼, 刘朝辉, 随志强. γ射线法测量高压管束间气液两相流的截面含气率分布[J]. 化工学报, 2019, 70(4): 1375-1382.

Figures/Tables 13

Fig.1 Schematic diagram of high-temperature and high-pressure steam-water test loop

Fig.2 Schematic diagram of test section structure

Fig.3 Schematic diagram of distribution of radial measuring points of pipe bundle section

Table 1 Measuring instruments parameters

测量参数	量程	测量仪表	精度
质量流量/(kg/h)	0～3000	RHEONIK 质量流量计	0.05%
进口压力/MPa	0～68	Rosemount3051压力变送器	0.1%
温度/℃	-200～400	Φ3 mm T型热电偶	±0.4℃
预热段功率/kW	0～700	电压电流变送器	0.1%

Table 2 Summary of uncertainties

测量参数	不确定度/%
进口压力/MPa	0.23
质量流速/(kg/(m² $?$ s))	0.26
热力学干度	5.02
体积含气率	5.97
截面含气率	6.75

Table 2 Summary of uncertainties

测量参数	不确定度/%
进口压力/MPa	0.23
质量流速/(kg/(m² $?$ s))	0.26
热力学干度	5.02
体积含气率	5.97
截面含气率	6.75

Fig.4 Distribution of void fraction in each section of vertical tube bundle

Fig.5 Diagram of steam motion

Fig.6 Average void fraction varied with thermodynamic dryness

Fig.7 Experimental result compared with Miropolskii calculated values

Fig.8 Experimental result compared with Smith calculated values

Fig.9 Experimental result compared with Armand calculated values

Table 3 Void fraction correlation discussed in this study

文献模型

经验关联式

适用条件

Miropolskii^[31]

α m = 1 1 + S ρ g ρ l 1 - x x

S = 1 + 2.27 ρ l 0.7 G 0.7 1 - P P c r

D=6.7~17.7 mm管束

Smith^[23]

α m = 1 + A S M 1 - x x ρ g ρ l

A S M = 0.4 + 0.6 ρ g ρ l + 0.4 1 - x x / 1 + 0.4 1 - x x

D=6~38 mm单管，G=650~2500 kg/(m²?s)

Armand^[29]

$α m = C β$

$C = 0.833 + l n P$

D=56 mm单管，G=2000 kg/(m²?s)