Experimental study on the heat transfer characteristics of steam-water two-phase flow in a 2×2 wire-wrapped rod bundle

Abstract

The Supercritical Water-Cooled Reactor (SCWR) is recognized as a promising nuclear reactor design owing to its elevated thermal efficiency and economic advantages. During transient operations or accident scenarios, reactor cores may experience subcritical pressure conditions. Therefore, the heat transfer characteristics of steam-water two-phase flow under subcritical pressure are crucial for the thermal-hydraulic design and safety assessment of SCWRs. The heat transfer characteristics of steam-water two-phase flow in a 2 × 2 wire-wrapped rod bundle were experimentally investigated. The effects of system parameters on heat transfer characteristics were analyzed. As the heat flux increased, the wall temperature in the single-phase region increased accordingly, but the heat transfer coefficient remained unchanged. In the saturated boiling region, the wall temperature stayed relatively constant, but the heat transfer coefficient improved with heat flux. The mass flux had a relatively weak effect, whereas an increase in pressure led to higher values in the wall temperature and heat transfer coefficient within the two-phase region. Several heat transfer correlations were selected for evaluation. It was found that the Kandlikar (1990) correlation showed the highest accuracy for saturated flow boiling. The critical heat flux associated with heat transfer deterioration was also examined. As the pressure increased, the critical heat flux and critical steam quality decreased, suggesting that higher pressure will exacerbate heat transfer deterioration.