Bubble diameter distribution and intergroup mass transfer coefficient in flows with phase change

The intergroup mass transfer term is investigated in the multigroup two-fluid model. Past intergroup mass transfer modeling is thoroughly reviewed, highlighting the limited applicability to phase-change flows due to the closure need of the intergroup mass transfer coefficient. The intergroup mass transfer coefficient is dependent on the bubble diameter distribution. The backward transform method, which is used to transform chord length distribution data to a bubble diameter distribution, is improved with a new regularization strategy which can better reduce the inherent instability of the inverse problem. Experimental data from phase-change flows are processed with the modified backward transform method to evaluate the bubble distribution and to determine the intergroup mass transfer coefficient. Analytical correlations for the intergroup mass transfer coefficient are developed, employing the Nukiyama-Tanasawa distribution function and the Rosin-Rammler distribution function. The benchmark with the experimental data demonstrates that the new correlations for the intergroup mass transfer coefficient are accurate over a wide range of two-phase flow conditions. In addition, a new empirical correlation for the intergroup mass transfer coefficient is developed from a regression of the experimental data.