内螺纹管临界热流密度预测与数值计算

基于壁面汽泡壅塞理论，针对近临界压力区两相流动沸腾的偏离泡核沸腾(DNB)现象，对垂直上升内螺纹管的DNB型临界热流密度(CHF)进行了数值计算研究。以内螺纹管为分析对象改进已有的汽泡壅塞模型，计算了汽泡层区与主流区的极限传递质量流量、湍流速度分布、汽泡层区临界截面含气率等本构关系，汽泡脱离直径的计算考虑了汽泡接触角的影响。本文模型还根据大量CHF实验数据拟合得到了新的α_b关联式。最后，基于Fortran语言编制了CHF的理论预测数值模型程序，研究分析了压力、质量流速、热平衡干度及进口欠焓对CHF的影响，并根据CHF查表值对本文模型进行评估，同时将实验得到的内螺纹管CHF数据与采用Bowring模型、Katto模型、Shah模型和本文模型计算的CHF进行比较，发现本文模型的误差最小，与实验值吻合结果较好，说明本文模型能较好地对垂直上升内螺纹管DNB型CHF进行预测。

Prediction and Numerical Computation of Critical Heat Flux in Rifled Tube

Based on the theory of bubble coalescence in the wall bubbly layer, for a deeper understanding of departure from nucleate boiling (DNB) in two-phase flow boiling under near-critical pressures, critical heat flux (CHF) of DNB type in a vertical upward rifled tube was numerically studied. Some improvements of the existing bubble coalescence model were proposed for the rifled tube. Meanwhile, the limiting transverse interchange of mass flux crossing the interface of the bubbly layer and core region, the turbulence velocity distribution, critical void fraction of the bubbly layer and other constitutive relations were determined. The influence of the bubble contact angle was taken into account in the detached bubble diameter calculation. The new α_b empirical correlation was proposed through fitting a large number of CHF experimental data. Finally, based on Fortran language, the theoretical prediction numerical model of CHF was developed. The effects of pressure, mass flux, equilibrium quality and inlet subcooling on CHF were analyzed. The model was evaluated by the values of CHF Look up Table. And the comparison between the predictions by Bowring model, Katto model, Shah model as well as the present CHF model and the experimental CHF data shows the best agreement of the proposed model, indicating that the proposed model can predict CHF of DNB type well for the vertical upward rifled tube.