Abstract
We have made a simple loop-type thermoacoustic engine that will be used for a refrigerator and examined a temperature gradient in the stack and pressure amplitude of oscillation along the loop tube by changing supplying heater power, the mesh size of stack, and the charge pressure of helium gas in the loop tube. The temperature gradient in the stack decreases remarkably in the small values of ωτ and increases in the large values of ωτ as ωτ increases, where ω is the oscillation frequency and τ is the thermal relaxation time between stack materials and helium gas. This result shows an optimum value of ωτ in the minimum onset temperature gradient of oscillation. We have tried to find the efficiency of energy conversion in the stack by assuming that the acoustic wave could be expressed as the superimposition of the standing wave component and the progressing wave component that attenuates linearly along the loop. It is found that the maximum efficiency in this work was about 30% and the energy losses in the stack may depend on its mesh size.
