Akira Kawamoto

Convective heat transfer induced by fluid oscillations

Numerical simulation was conducted on the heat transfer process in a two-dimensional flow field imposed by a sinusoidal oscillation of the fluid. When gravitational force was ignored, the heat transfer at the wall was similar to forced-flow turbulent heat transfer. On the other hand, considering gravity, two modes of mixed convection heat transfer were observed depending on the thermal boundary conditions. For high-viscosity fluids, a bifurcation of the flow pattern appeared, which was mainly determined by the oscillation amplitude.

Temperature distribution along stack in an acoustic-resonance tube : Discussions on advanced linearized theory

Verification of the applicability of the linearized thermoacoustic theory proposed in 1988 by Swift, J. Acoust. Soc. Am., 84, (4), 1145–1180, to an acoustic- resonance tube refrigerator and discussions on the advanced linearized theory were conducted through a comparison with the measured temperature distribution along the stack in a simulated acoustic-resonance tube. The measured temperature in all cases of various stack configurations such as stack plate spacing and length showed an almost linear distribution along the stack, while Swifts linearized theory gave a curved distribution with relatively large deviation from experimental data. Eddy diffusivity and/or steady streaming effects excited by sound waves were taken into account in the linearized model, and the effects of these terms on the prediction of temperature distribution were examined. The agreement between theory and experiment was markedly improved by the introduction of steady streaming. This provided a guideline for the construction of an advanced linearized theory.

Heat Transfer in an Acoustic-Resonance Tube Model and Its Visualization.

The resonance tube refrigerator developed by Wheatley et al. has given rise to great interest in the field of refrigeration technology. Fundamental investigation has been conducted on the resonance tube refrigerator using a simplified model. The temperature response of the stack in the tube has been visualized by using a thermosensitive liquid-crystal sheet. The visualized image has demonstrated the heat-transfer mechanism based on the thermoacoustic theory. The temperature distribution in the tube has been discussed with reference to the resonance tube configuration, the mode of resonance and the working fluid property.