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Study of Rapid Heat Transfer Phenomena of Nano-second

纳秒快速传热现象研究

基本信息

批准号：
10650200
负责人：
SHOJI Masahiro
金额：
$ 2.18万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650200/
关键词：
Rapid heat transfer Laser irradiation Shock wave Heating in liquid Heating of metals 急速加熱相変化蒸気爆発

项目摘要

The experimental and theoretical study of laser pulse heating of metal surfaces was conducted in water to make clear the physics of heat and fluid flow phenomena in nano-second order. In the experiment employing mercury as the test surface, it was found that the shock wave due to phase change of water and mercury is generated just after laser irradiation and, at the next stage of milli-seconds, a semi-spherical vapor bubble is formed and , in the last stage of a few seconds, the deformation of mercury surface is followed. In contrast, in case of heating in air, plasma of mercury appears in several micro-seconds after the irradiation accompanied by shock wave without deformation of mercury surface. In the experiment employing the silicon solid surface in water, a strong shock wave appears due to the phase change of water which travels in water with the speed of sound velocity. The phase change may be understand to occur when the surface temperature of silicon reaches the homogeneous nucleation temperature of water. In the case of heating of silicon surface in air, the shock wave is observed but this is mainly due to the expansion of air. In order to explain those experimental results, simple model of shock wave generation is proposed basing on the facts that (1)heat transfer is governed by usual parabolic heat conduction (non-Fourier and quantum effects are not significant) ; (2) liquid convection can be neglected but compressibility of water becomes important ; (3) phase change takes place when the metal surface reaches the homogeneous nucleation temperature of water, which yields the shock wave. This model explain well the dependence of shock wave strength on laser irradiation power.

为了弄清纳秒量级的热物理和流体流动现象，对水中金属表面的激光脉冲加热进行了实验和理论研究。在采用汞作为试验表面的实验中，发现由于水和汞的相变而产生的冲击波在激光照射后立即产生，在毫秒的下一阶段，形成半球形蒸汽泡，在几秒钟的最后阶段，汞表面变形。与此相反，在空气中加热的情况下，汞的等离子体出现在几个微秒的照射后，伴随着冲击波没有变形的汞表面。在利用硅固体表面在水中进行的实验中，由于水的相变，以声速在水中传播，出现了强烈的冲击波。可以理解，当硅的表面温度达到水的均匀成核温度时发生相变。在硅表面在空气中加热的情况下，观察到的冲击波，但这主要是由于空气的膨胀。为了解释这些实验结果，基于以下事实提出了冲击波产生的简单模型：（1）传热受通常的抛物线热传导控制（2）液体对流可以忽略，但水的可压缩性变得重要;（3）当金属表面达到水的均质形核温度时发生相变，产生冲击波。该模型很好地解释了冲击波强度与激光辐照功率的关系。