Examination of Wetting Behavior on High Superheated Surface with Chemical Thermodynamics

高过热表面润湿行为的化学热力学检验

基本信息

批准号：
11650235
负责人：
OHTAKE Hiroyasu
金额：
$ 2.3万
依托单位：
Kogakuin University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650235/
关键词：
Mechanical Engineering Thermal Engineering Boiling Wetting Thermodynamic Limit of Superheat Liquid-Solid Contact Correlation of Transition Boiling Advancing and Receding Contact Angle 遷移沸騰熱力学的過熱限界温度接触角熱伝達極小熱流束点

项目摘要

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

过热表面再润湿现象的物理机制仍然是尚未解决的重要问题，众所周知，过渡沸腾传热和最小热通量点与“一定的接触角”密切相关，但目前尚不清楚。接触角控制沸腾现象。实验研究了薄膜沸腾崩溃过程中高过热表面的再润湿行为。在实验中，从喷嘴向稳定的过热表面提供液体射流。实验结果表明，当局部壁温低于300℃（即热力学极限）时，汽膜发生局部扰动，导致汽膜局部崩溃。随后，随着液体射流的流速降低，蒸汽膜在 250℃ 左右开始崩溃。随着初始壁面过热度的降低，后退速度增大，液-汽界面线与受热壁面之间的夹角分别接近于室温下的动态前进和后退接触角。通过水平向上的平板铜板的稳定传热实验研究了水的过渡沸腾传热。在过渡沸腾中，过渡沸腾到核态沸腾的加热过程的传热特性与冷却过程的传热特性相似。从薄膜沸腾开始，通过关注无量纲壁过热度，从现有的实验数据中推导出过渡沸腾传热的相关性和模型。过渡沸腾传热是使用宏观层模型开发的。