Modeling of subcooled flow boiling for hypervapotron in divertor of fusion reactor based on RPI model

The divertor is the key in-vessel component to remove the high heat flux and impurities in magnetic confinement fusion reactor. Hypervapotron (HV) has been developed as one of the candidates for cooling structure of divertor, owing to its excellent heat transfer performance in subcooled flow boiling. To address the design and development requirements of divertor, a suitable model for single-phase and two-phase flow of HV are developed. Four combination models of boiling properties expressed by different empirical correlations are evaluated. The results indicate that the LC-UN (Lemmert-Chawla, Unal) model shows a good agreement with the experimental results of Lim et al. (2022), with average deviation of 8.15%. Moreover, for the first time, the model successfully predicts the onset of fully developed nucleate boiling (OFDB) point of HV. Based on the LC-UN model, the detailed heat transfer and flow characteristics of HV are revealed. It shows that the boiling process is independent between each slot due to the fin barrier, and the bubbles are condensed by the subcooled main stream after leaving the wall. The “double vortex” in HV intensifies the interaction between vapor and liquid phase, preventing the aggregation of bubbles, allowing it has excellent heat transfer performances.