过冷流动沸腾汽泡浮升直径的理论研究
Theoretical Analysis of Bubble Lift-off Diameter in Subcooled Flow Boiling
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摘要: 汽泡浮升直径模型已成为两相流领域理论分析与数值计算方法的重要子模型。为研究各力对汽泡浮升的影响规律，本文理论推导了过冷流动沸腾汽泡的受力方程，建立了预测汽泡浮升直径的无量纲模型，并与实验数据进行了对比验证，分析了汽泡浮升直径随各无量纲数的变化规律。结果表明，无量纲模型能准确预测水与R113工质中汽泡的浮升直径；浮升直径随Ja的增加而升高，随Re、Ca、Pr与Ar的增加而降低；结合无量纲数的定义，可认为生长力与表面张力抑制了汽泡的浮升效应，导致浮升直径升高；剪切升力与浮升力促进了汽泡的浮升效应，导致浮升直径降低。Abstract: Bubble lift-off diameter model is one of the most important sub-models in the field of two-phase flow and numerical computation method. In order to study the influence of different forces on bubble lift-off, theoretical analysis was carried out about the force equation of a single bubble in subcooled flow boiling, which proposed a dismensionless model for the prediction of bubble lift-off diameter. The comparison between predictions and experimental data, which involved water and R113, was made and the changing rule of bubble lift-off diameter as dimensionless numbers was analyzed. The results show that the predicted lift-off diameters agree well with the experimental values of water and R113. Bubble lift-off diameter increases with Ja and decreases with the increase of Re, Ca, Pr and Ar. Combined with the definition of dimensionless numbers, it is concluded that the growth force and the surface tension force restrain bubble from departing the wall, which results in a larger lift-off diameter. The shear lift force and the buoyance force promote bubble to depart, causing the decrease of lift-off diameter.
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