Abstract
Thermally driven acoustic oscillation is one of nuisances for cryogenic researches and applications, because it disturbs measurements and accompanies a considerable amount of heat flux into low temperature devices. This paper reports a rough picture of the thermally driven acoustic oscillation and some information on the stability limit of the oscillation. Corresponding two types of experiments were carried out using helium gas.
The first type of experiments shows that
1. Periods of the oscillation and temperature distribution in the dewar suggest the oscillation is one of gas-column oscillations.
2. The oscillation amplitude is very sensitive to inner radius of the tube.
3. Heat flux into the dewar due to the oscillation is roughly proportional to the square of the oscillation amplitude.
The second type of experiments with U-shaped tube shows that
4. The stability limit of the oscillation is expressed by dimensionless quantities, TH/TC and ατ/r2, where TH and TC are temperatures of hot and cold parts and α, τ and r are the thermal diffusivity of the gas at the hot part, the oscillation period and the inner radius of tube, respectively.
5. The calculations of the stability limit by N. Rott are confirmed experimentally.
6. The stability limit is expressed by a simple relationship between TH/TC and ατ/r2.
