CHF ON CYLINDERS - REVISIT OF INFLUENCES OF SUBCOOLING AND CYLINDER DIAMETER

摘要

CHF is an important topic of boiling. The commonly accepted figure on the scaling of CHF, which is built upon the experimental data obtained in normal gravity, has received strong challenges from microgravity researches recently. It is found that CHF on cylinders in microgravity show the same trend as the prediction of the correlation of Lienhard & Dhir (1973), although the dimensionless radius is extended to over two decades of the original lower value of the correlation. The present paper reports a new series of experimental data of CHF on cylinders in normal gravity. Platinum wires of 30 mm in length are simultaneously used as heaters and thermometers. Their diameters are 0.1, 0.06, and 0.025 mm, respectively. FC-72, R113, and acetone are used as working fluids. The range of the subcooling is from 0 K to about 50 K. It is much evident that the cylinder diameter has an influence on the dependence of CHF on subcooling in the case of small cylinder diameter. Thus, it's conjecturable that there may exist some other parameters in addition to the Bond number that play important roles in the CHF phenomenon with small Bond number.