Study on the refrigeration performance of a miniature pulse tube cryocooler driven by a gas bearing compressor

Recent advancements in long-term space exploration, maintenance-free miniature-satellites and drone infrared detections have created a large demand for highly reliable and miniaturized cryocoolers working at 77-150 K. The pulse tube cryocooler (PTC) has no moving part at the cold end, and if driven by a gas bearing linear compressor which has no mechanical fatigue risk, a refrigeration system with high reliability and compactness will be generated. However, very few researches on the cooling performance of PTC driven by gas bearing linear compressor have been reported. In this study, a miniature PTC and gas bearing compressor are developed, with a weight of the whole refrigeration system about 0.97 kg. The maximum cooling capacity reaches 1.73 W at 77 K with input electric power of 66 W. The cooling capacity per unit weight for this cryocooler is 1.78 W/kg at 77 K, which is the highest compared to those of the existing typical miniature cryocoolers, showing its remarkable lower mass for refrigeration. In addition, the influence of the hot end heat dissipation temperature on the cooling performance is studied. It is found that the heat dissipation temperature of the hot end has a significant effect on the cooling performance. For every 10 K decrease in the hot end temperature, the maximum cooling capacity at 77 K increases by 3.45 % to 13.28 %, the relative Carnot efficiency rises by 4.38 % to 12.59 %. Besides, in the miniature PTC, the cooling performance is very sensitive to the length of the inertance tube, even a small change of 10-20 mm on the length of the inertance tube will lead to obvious effect on the optimum frequency and cooling performance of the system. These results will be helpful for the further research and development of the miniature pulse tube cryocoolers.