Temperature Distribution and Heat Transfer in Narrow Channel during Thermoacoustic Oscillation

Abstract

Thermoacoustic oscillation is induced when a gas is in a tube with a narrow channel section that has a large temperature gradient. Although the oscillation in the tube section was studied, that in the narrow channel has not yet been discussed well. The temperature distribution and the heat transfer in the narrow channel section, which are the most important parameters for the design of thermoacoustic devices, are discussed in this study. Numerical calculations of fluid conservation equations are performed, and the onset of oscillation is obtained by gradually increasing the temperature gradient. The minimum onset temperature ratio is shown to agree with the existing analytical and experimental results. The average wave speed is in between the isothermal sound speed for the highest temperature and the adiabatic sound speed for the lowest temperature. The distribution of oscillating temperature in the narrow channel is found to be different and reversed from that in the tube. It is shown in the narrow channel that the heat transfer is smaller for larger diameter and larger for smaller diameter and the heat transfer coefficient or the heat transfer model should be improved for the oscillating flow.