| Research Abstract |
Increasing attention has been given to the development of an acoustic resonance refrigerator for space use and other applications of small-capacity, owing to the environmental importance. This project focused on the fundamental understanding of the heat transfer mechanism by thermo-acoustics. A simulated acoustic refrigerator model was constructed, consisting of an acoustic actuator, a resonance tube and a stack, and acoustic characteristics as well as the temperature distribution along the stack were measured. The results obtained in this project were summarized as follows.
1. Maximum temperature difference across the stack reached 30 K,using helium or nitrogen gas as a working fluid. The Improvement of acoustic actuator will make the possibility of practical refrigerator high.
2. The acoustic field was well predicted using a linearized acoustic theory, while the linearized theory gave poor results at higher acoustic amplitude. Improving the model to taking into account the nonlinear ef
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fect, the fundamental characteristics of acoustic field could be predicted even at high-amplitude region.
3. Temperature distributions along the stack were significantly affected by the acoustic amplitude, stack length, the position of stack relative to the amplitude distribution. The distance between successive stack plates plays an important role on the thermo-acoustic behavior including the temperature difference as well as the phase difference of acoustic wave across the stack. Some optimum stack-plate distance existed. When the acoustic amplitude was at lower level, the linearized thermo-acoustic theory could well predict the temperature distribution, while at high amplitude non-linear effect became to have a significant influence on the temperature distribution. Taking into account the effect of acoustic Reynolds stress and resulting acoustic streaming and eddy diffusivity, the prediction model was improved to give better agreement with the experimental results. Further experimental investigation will be needed in the heat transfer at the stack surface, but the present results of this project gives satisfactory understanding of the principal feature of the thermo-acoustic refrigerator. Less
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