1991 年 26 巻 2 号 p. 98-107
Pulse-tube refrigerators are attractive as long life and highly reliable coolers because of their mechanical simplisity. The early type of the device, which was first developed by Gifford and Longsworth in the early 1960's, is known as the “basic pulse-tube”. In the 1980's, the “orifice pulse-tube”, which originated from Mikulin's work, was shown by Radebaugh et al. to possess high cooling capability. This was the start of the boom of pulse-tube refrigerator research and development and many laboratories around world are now studying these devices. This paper briefly reviews the developments of several types of the pulse tube refrigerators, and an explanation of the cooling mechanism in terms of the thermoacoustic effect is presented. According to the thermoacoustical consideration, tremendous differences in refrigeration power between the basic and orifice types can be understood as follows; flow impedance of an orifice enhances the progressive-wave part of the working gas oscillations which causes large increases in heat transfer through a regenerator. Finally, some experimental data from the author's laboratory are shown and a qualitative interpretation by analogy with an AC circuit is described.