抄録
In this paper, we report the direct observation of the energy conversion in a narrow tube having a temperature gradient. A gas parcel in the tube was driven by an oscillating piston at 1.00Hz to assure good thermal contact with the tube wall. We measured the oscillations of pressure and velocity in the tube to determine the acoustic intensity in the tube. We observed the amplification of the acoustic intensity in the region having a positive temperature gradient. We derived specific volume oscillation of the gas parcel from the measured pressure and temperature. The increase of the acoustic intensity per unit length was in good agreement with the enclosed area in the plot of pressure versus specific volume. This represents that the amplification of the acoustic intensity results from the thermodynamic cycles experienced by the gas parcel.
