Onset of Nucleate Boiling in Natural Circulation Systems Predicted Using the Second Stir Theory

• Published in: Tsinghua science and technology 2010, Vol.15 (4), p.441-446
• Main Author: 周涛 杨瑞昌 李臻洋 张明 刘梦影
• Format: Article
• Language: English
• Subjects: boiling; direction; natural circulation; onset of nucleate boiling (ONB); second stir theory; 二次搅拌; 核沸腾; 流动参数; 环流系统; 自然循环系统; 质量流量
• ISSN: 1007-0214; 1878-7606; 1007-0214
• DOI: 10.1016/S1007-0214(10)70085-7

Experimental data and calculated results for the onset of nucleate boiling （ONB） in natural circula- tion systems show that for the same operating conditions, the equilibrium vapor quality for ONB in natural circulation is lower than for forced convections. The differences can be explained using second stir theory. The weak vortices and small stir energy in natural circulation systems result in nucleate boiling occurring earlier than in forced convection systems. In natural circulation systems high mass flow rates are accompa- nied by large kinetic energies and large stir energies, which enables changes in the directions of flow eddies and energy transport. The equilibrium vapor qualities at ONB are then higher at higher mass flow rates. The influence of other flow parameters on ONB can be evaluated by the relationships between these flow pa- rameters and the mass flow rate. The same values can lead to different results due to different eddy direc- tions. This indicates that the quantitative comparability in mathematics cannot be considered as only scien- tific standard. The second stir theory offers a new visual angle for researches on natural circulation.