Examination of Wetting Behavior on High Superheated Surface with Chemical Thermodynamics

过热表面再润湿现象的物理机制一直是未解决的重要问题。过渡沸腾传热和最小热流密度点与“一定的接触角”密切相关，但接触角如何控制沸腾现象还不清楚。实验中，在稳定的膜态沸腾状态下，从喷嘴向过热表面喷射液体射流，然后观察润湿面积。实验结果表明，当壁面局部温度低于300℃时，汽膜内发生局部扰动，导致汽膜局部塌陷，的热力学极限。随后，在约250℃时，蒸汽膜开始破裂。随着液体射流流量的减小，温度降低。在液体- ...更多信息 壁面接触和再湿前缘的推进速度随初始壁面接触的减小而增大。随着壁面初始温度的升高，后退速度增大。在室温下，汽液界面线与被加热壁面的夹角分别接近于动态前进角和后退角。通过水平向上平板铜板的稳态沸腾传热实验，研究了水的过渡沸腾传热。在过渡沸腾中，加热过程通过核态沸腾过渡沸腾的传热特性与膜态沸腾开始的冷却过程的传热特性相似。根据实验数据导出了过渡沸腾传热的关联式和模型。通过关注无因次壁面过热度，得到了过渡沸腾液固接触分数的关联式。采用宏观层模型建立了过渡沸腾传热模型。少

The physical mechanisms of the rewetting phenomena on a superheated surface are still unresolved important issues. It is common knowledge that transition boiling heat transfer and minimum-heat-flux point are related to "a certain contact angle" closely, however it is not clear how contact angles control boiling-phenomena.The behavior of rewetting on high superheated surface during collapse of film-boiling was investigated experimentally. In the experiments, a liquid jet from a nozzle was supplied on the superheated surface in the stable film-boiling, and then the wetted area was observed. The experimental results showed that the local disturbance in the vapor film occurred to induce the local collapse of the vapor film when the local wall temperature was below 300℃, i.e., the thermodynamic limit of superheat. Sequentially, the probative collapse of the vapor film began at about 250℃. The temperature was lower as the flow rate of liquid jet decreased. The wetted area right after liquid- … More wall contact and the advancing velocity of the rewetting front increased as the initial wall superheat decreased. The receding velocity increased with the initial wall temperature. The angles between the liquid-vapor inter facial line and the heated wall were close to the dynamic advancing and receding contact-angles in room temperature, respectively.Transition boiling heat-transfer of water was examined by steady heat transfer experiments for horizontal upward-facing flat copper plate. In the transition boiling, heat transfer characteristics for heating process run in transition boiling through nucleate boiling were similar to those for cooling process started from film boiling. Correlations and a model of the transition boiling heat-transfer were derived from the present experimental data. The correlations of fraction of liquid-solid contact in the transition boiling were obtained by focusing on the dimensionless wall superheat. The model of the transition boiling heat-transfer was developed by using the macrolayer model. Less