Studies of transition boiling heat transfer with saturated water at 1-4 bar. Final report

Steady-state and transient transition boiling heat transfer tests with water at low pressures have been conducted using a loop in which the test sections were heated by hot mercury. A revised heat transfer correlation was developed which provides a better fit of all the data. Transient heat transfer data in the transition boiling region were obtained in two separate test sections, in which the transient was initiated by a sudden increase of the water flow rate. Comparison indicates that the new heat transfer correlation also applies to transient data. The rewetting rates were dependent on local void fraction and test section geometry. At high void fractions in the annular test section, the rewetting rate was determined by the availability of cooling water to the heated surface. Phenomenological studies included void fraction measurement, visual and photographic observations and an examination of wall temperature fluctuations. In essentially all the experiments, the water was at the saturation temperature when transition boiling began.