立式螺旋管内亚临界水-水蒸气两相流截面含气率研究及预测模型建立OA

The helical tube steam generator,recognized for its compact structure and high heat transfer efficiency,has emerged as a crucial component in the design of fourth-generation nuclear reactors.This study investigated the distribution of cross-sectional void fraction(α)in high-temperature,high-pressure(HTHP)water-steam two-phase flow within helical tubes under subcritical pressure conditions.A γ-ray measurement platform was established,and experiments were conducted across a wide range of operational conditions.The experimental results indicated that the α increased with an increase in thermal equilibrium quality(x).Furthermore,the relationship between α and volume void fraction(β)was determined to be piecewise linear.Based on this,flow patterns within helical tubes were classified into bubble,slug,and annular flow.A new prediction model for the α in water-steam two-phase flow within helical tubes under subcritical pressure conditions was developed,incorporating experimental data and previous literature.The model incorporated flow pattern distinctions and was rigorously validated against experimental data,demonstrating significant improvements in prediction accuracy.Compared to existing prediction models,the new model achieved a 47.5%and 15.6%increase in prediction accuracy for the bubble and slug flow regions,respectively.This model could provide valuable insights for the design of helical tube steam generators in fourth-generation nuclear reactors.