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

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. © All Right Reserved.