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MICRO-HEAT TRANSFER MECHANISM IN A BOUNDARY LAYER INDUCED BY ACOUSTIC OSCILLATION AND THE DEVELOPMENT OF THERMOACOUSTIC THEORY

声振荡引起的边界层微传热机制及热声理论发展

基本信息

批准号：
09650257
负责人：
OZAWA Mamoru
金额：
$ 1.92万
依托单位：
KANSAI UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650257/
关键词：
Acoustic refrigerator Temperature distribution along stack Acoustic streaming Heat transfer Control of phase lag Flow visualization Osccillation boundary layer スタック熱伝逹バイパス可視化

项目摘要

It is well known that the boundary layer is formed by a sinusoidal oscillation. The thickness of this boundary layer (referred to as the depth of penetration) and thermal flow behavior there control the system performance of acoustic resonance-tube refrigerator. The scaling parameters of such heat transfer are derived based on the theoretical and numerical analysis as follows : the Prandtl number, the oscillation Reynolds number, the Strohal number with respect to the amplitude of fluid oscillation and the stack distance, the Strohal number with respect to the amplitude and the stack length and the heat capacity ratio of the stack and the fluid. Comparison between the experimental data of temperature distribution along the stack and the linearized thermoacoustic theory indicated a prime importance of the Strohal number. One of the important factors related to the Strohal. number is an acoustic streaming induced by the existence of fluid viscosity. Then the flow visualizing study was conducted to look insight into the influence of the stack on the streaming. The acoustic streaming showed characteristic feature that two vortices appeared at both sides of the stack and moreover that these two vortices were combined with each other by the through flow between them. This suggested the importance to take such vortices and through flow into account in the development of prediction model. Alternative approach to improve the performance is the control of the phase difference between the velocity and pressure fluctuation, and/or veloci es at both ends of the stack. One of the typical techniques is to install the by-pass between the acoustic driver and the closed end of the resonance tube. Then the by-pass with a resonance box has shown the potential to improve the performance.

众所周知，边界层是由正弦振荡形成的。边界层的厚度（即穿透深度）和边界层内的热流行为决定了声谐振管制冷机的性能。通过理论分析和数值计算，得到了该传热过程的标度参数：Prandtl数、振荡雷诺数、与流体振荡幅度和叠层间距有关的Strohal数、与振幅和叠层长度有关的Strohal数以及叠层与流体的热容比。通过对叠层沿着方向温度分布的实验数据与线性化热声理论的比较，表明了Strohal数的重要性。其中一个重要因素与斯特罗哈尔有关。数是由流体粘性的存在引起的声流。在此基础上，进行了流场可视化研究，探讨了叠层对流动的影响。声流的特征是在叠层的两侧出现两个涡，而且这两个涡通过它们之间的通流相互结合。这表明在发展预测模型时考虑这种涡和通流的重要性。另一种改进性能的方法是控制速度和压力波动之间的相位差，和/或在叠层两端的速度。典型的技术之一是在声学驱动器和谐振管的封闭端之间安装旁路。然后，与谐振箱的旁路已经显示出改善性能的潜力。