竖直矩形窄流道内汽泡生长的实验研究

Experimental Study on Bubble Growth in Vertical Narrow Channel

在1个大气压下对间隙为2mm的竖直矩形窄流道内向上过冷流动沸腾的壁面汽泡生长进行了可视化实验研究。用高速摄像仪以5000fps的速度拍摄512×512pixel的图片，得到了不同工况（变热流密度和变质量流量）下各汽泡的生长数据。计算了汽泡生长的平均当量直径（Dc）与汽泡生长时间的关系；拟合出汽泡生长的指数曲线。研究发现，拟合指数曲线可较好地预测窄流道内汽泡生长，拟合指数曲线的系数K和n值与传统大流道的情况有较大区别；K与Ja数的关系不像传统大流道那样明显；n值在0．339～0．914之间变化。

A visual investigation of vapor bubble growth in subcooled upward forced convection boiling in vertical rectangular narrow channel （the gap is 2 mm） was performed. High speed camera was used to record the bubble growth with a speed of 5000 fps（frames per second）, and the picture size are 512 × 512 pixel. Experimental results about bubble growth in various work conditions （with variation heat flux and mass flux） were recorded; and based on the regression analysis, the exponential fitting relationship between the mean equivalent bubble diameter（De） and the bubble growth time was revealed. The results show that the exponential fitting can predict the mean bubble growth in narrow channel very well; but the coefficients of K and n, are quite different with that of conventional channel; and the K is less dependent on Ja number other than that of conventional channel, and the n has the value of wider range of 0.339 - 0.914.