1998 Fiscal Year Final Research Report Summary
MICRO-HEAT TRANSFER MECHANISM IN A BOUNDARY LAYER INDUCED BY ACOUSTIC OSCILLATION AND THE DEVELOPMENT OF THERMOACOUSTIC THEORY
| Project/Area Number |
09650257
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | KANSAI UNIVERSITY |
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Principal Investigator |
OZAWA Mamoru KANSAI UNIVERSITY FACULTY OF ENGINEERING PROFESSOR, 工学部, 教授 (60112009)
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| Co-Investigator(Kenkyū-buntansha) |
UMEKAWA Hisashi KANSAI UNIVERSITY FACULTY OF ENGINEERING ASSISTANT, 工学部, 助手 (10232894)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Acoustic refrigerator / Temperature distribution along stack / Acoustic streaming / Heat transfer / Control of phase lag / Flow visualization / Osccillation boundary layer |
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| Research Abstract |
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.
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