The moving shock in gas wave tube of gas wave refrigerator was reflected back from closed end boundary of the tube. If the reflected shock wave was back to open mouth of the gas wave tube it will heat the expanded refrigeration gas at the open end

and reduce refrigeration efficiency severely. Analysis shown that pre-existing efficient tail end absorbing cavity type gas wave tube was not enough for attenuating and damping reflected shock

therefore a novel middle damping cavity type gas wave tube was put forward. By the contrastive analysis of motion wave train in both tubes

the comprehensive mechanism of the middle damping cavity were uncovered

those include damping reflected shock

turning back reflected shock to backend section of the tube

and converting part of the incoming shock wave to expansion wave which may counteract the reflected shock wave of escape from damping cavity. Computational fluid dynamics numerical simulation shows that the new type of gas wave tube could improve the refrigeration efficiency by 7%-11% relatively if the gas injection frequency higher than the second high efficient frequency

and trough efficiency about 18% relatively

so the refrigeration efficiency curve tends to smooth. The two cavities type gas wave tube combined by middle damping cavity and existing tail end absorbing cavity could improve the refrigeration efficiency corresponding to the low and medium frequency gas injection by 6%-8% relatively. The efficiency curve was more smooth. Refrigeration efficiency of three type gas wave tubes were measured and compared by the single gas wave tube model experiment. The performance of high efficiency and smooth efficiency curve of new type gas wave tube were proved. The amplitude contrast and trends of refrigeration efficiency of three type gas wave tubes and gas injection frequency corresponding to peak and trough points of efficiency

were in conformity with the simulation results.