Mechanisms and characteristics of micro-layer configuration in phase change heat transfer between liquid and vapor

液汽相变传热微层结构机理及特征

基本信息

批准号：
17360096
负责人：
UTAKA Yoshio
金额：
$ 10.18万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17360096/
关键词：
heat transfer phase change heat transfer boiling mini-channel nucleate boiling micro-layer laser extinction method 熱電熱

项目摘要

To elucidate the mechanism and characteristics of boiling heat transfer in a narrow gap micro-channel vaporizer, the experimental investigation concerning the micro-layer thickness that formed between the heating surface and vapor generated was performed. The micro-layer thickness was measured applying the laser extinction method for the channel gap sizes of 0.5, 0.3 and 0.15 mm. The configuration of thin liquid micro-layer distributions on the surface was clarified. The gap size, the rate of bubble growth and the distance from the incipient bubble site have an effect on the micro-layer thickness. The initial micro-layer thickness increased with increase of the velocity of bubble forefront to moderate value of the velocity. In the region of larger velocity, the thickness was constant for each gap. The distributions of the initial thickness of micro-layer on the surface were shown. Furthermore, the mechanism and characteristics of heat transfer was investigated quantitatively by analyzi … More ng the affecting factors such as the position of vapor bubble generated, the velocity of vapor forefront, the periods of the micro-layer dominant and the liquid saturation in a boiling cycle and so forth.The configuration of micro-layer formed under growing bubble in nucleate pool boiling was investigated. Micro-layer thickness was measured by specially devised measuring system applying the laser extinction method. The thickness of the initially formed micro-layer was decided uniquely. Furthermore, the study is carried out to elucidate the contribution of micro-layer on heat transfer on the basis of the measurement of configuration of micro-layer. The dominant factors determining the characteristics of micro-layer such as micro-layer thickness distribution, duration of micro-layer existence, the size of micro-layer area and so-forth were expressed by non-dimensional form on the basis of the similarity of bubble growth rate. Finally, the contribution of the evaporation from the micro-layer in nucleate boiling was shown. Less

为了阐明在狭窄的间隙微通道蒸发器中沸腾传热的机理和特性，进行了有关在加热表面和产生的蒸气之间形成的微层厚度的实验投资。测量微层厚度，应用激光扩展方法的通道间隙尺寸为0.5、0.3和0.15 mm。阐明了表面上稀薄的液体微层分布的构型。间隙尺寸，气泡生长速率和与初始气泡位点的距离对微层厚度有影响。最初的微层厚度随着气泡森林速度的增加而增加，速度的现代价值。在较大速度的区域中，每个间隙的厚度恒定。显示了微层在表面上的初始厚度的分布。此外，通过分析进行了定量研究热传递的机制和特征……更多的影响因素，例如产生的蒸气气泡的位置，蒸气最前沿的速度，微层的速度，微层占主导地位的时期以及在沸腾周期中的液体安全性的时期，等等。研究了在核池沸腾中生长的气泡下形成的微层的构型。微层厚度是通过使用激光扩展方法的专门设计的测量系统来测量的。最初形成的微型层的厚度是独特的。此外，该研究是为了根据微层的构型测量，以阐明微层对传热的贡献。确定微层特征的主要因素，例如微层厚度分布，微层存在持续时间，微层面积和SO-Forth的大小，以非少量形式表达，基于气泡生长速率的相似性。最后，显示了经济在核沸腾方面的经济贡献。较少的