Study of Void Fraction in Subcooled Flow Boiling through a Vertical Narrow Annular Channel

摘要

Using distilled water as the working fluid, the experiments with dual tube heating were made under four types of test section. The values of the onset of nucleate boiling Zonb could be measured in the experiments. And the values of the start of fully developed subcooled boiling Zfdb were calculated by Bowring method. Applying improved Rouhani-Axelsson mechanistic model, which consider the influence of mass flux, and Zuber-Findlay correlation, the differential equations including steam quality x, liquid subcooled temperature θ1 ,distance along the heated channel measured from the inlet Z and void fraction α were developed. The fourth-order Runge-Kutta method was used to integrate the relative equations simultaneously along the heating section while the experimental data were the initial conditions. The calculation results of the improved correlation were compared with the data of numerical calculation and agree well with it while the deviation was less than ± 12% .