Advances in pulse tube refrigeration

Abstract

The pulse tube refrigerator is now being developed for a wide variety of cryogenic cooling applications, and it is beginning to replace other types of cryocoolers in many of these applications. This widespread interest occurs because there are no moving parts in the cold end. Most of this development in pulse tube refrigerators began in the mid-1980s with the introduction of the orifice to provide the proper phase relationship between the gas velocity and the pressure. The pulse tube refrigerator has now become the most efficient cryocooler for temperatures of 60 to 120 K. The current state-of-the-art in pulse tube refrigerators is discussed in this paper. Temperatures as low as 2.2 K with two stages and efficiencies as high as 19% of Camot at 80 K in one stage have been achieved. The operating fundamentals are explained very well through the use of thermoacoustic modeling techniques. Recent R&D areas to be discussed are the use of additional orifices, inertance tubes, tapered pulse tubes, dc flow, and thermoacoustic drivers. The fluid dynamics within the pulse tube is still not well understood, and further research in this area is needed to improve performance even further.