Regenerator losses are discussed in terms of the thermoacoustic theory. The phase difference (θ) between pressure oscillation and displacement of gas is one of key parameters for a regenerator's performance. Rough analyses show that contributions of the standing wave component, Wstand and Qstand, proportional to cosθ can be used to increase efficiency. Considering the distribution of θ in a regenerator, the highest efficiency is expected in the case that cosθ at the hot end is zero. In this case, it is possible to increase operation frequency. Including these results, the thermoacoustic theory succeeds in explaining qualitatively recent experimental findings on the effects of valve timing to the performance of a 2-stage-4 K-GM cryocooler.
