Drift-flux model of sub-channel in vertical rod bundles with spacer grids

Drift-flux model has been one of the most popular models predicting two phase flow parameters in nuclear reactor and other industrial equipment since proposed. Most of researches are based on the void fraction measurement on the whole cross-section of the void fraction, which is under the influence of casing tube and might be unfit for sub-channel. Therefore, experiments have been performed to measure the void fraction in sub-channels with the newly designed impedance void meter, based on which the existing drift-flux correlations have been evaluated. However, few correlations have good performance in bubbly and cap bubbly flow. In order to improve the accuracy and consider the physical significance, the new correlation of distribution parameter is proposed by adopting Julia's drift velocity correlation. The proposed correlation could predict the present data, Yang's data and Clark's data with the mean relative error of 13.96%, 16.23% and 24.9% respectively. Furthermore, the L/D effect on distribution parameter has been analyzed with different spacer grids. The mixing vane spacer grid (MVSG) results in a larger value of distribution parameter than simplified spacer grid in low void fraction region for the stronger recirculating flow.