DNB Oscillatory Temperature and Thermal Stress Responses for Evaporator Tubes Based on Rivulet Model

Experiment evidence and observations have shown that the DNB oscillation phenomena can best be characterized by water rivulets motion with temperature variation in the circumferential direction. This paper presents the rivulet thermal model that directly corresponds to these observations. Finite element computer codes were used to evaluate temperature and thermal stress behavior of the steam tube under the condition where water rivulets appear and disappear along the tube inside circumference. An inherently complicated three-dimensional problem can reasonably be reduced to a two-dimensional analysis with relative simplicity.