Research on the Cold Inertance Tube and Active Warm Displacer in an 8 K Pulse Tube Cryocooler

As an important component of the Stirling-type pulse tube cryocooler (SPTC), an efficient phase shifter can significantly improve the cooling capacity. This paper combines the advantages of the cold inertance tube and reservoir (ITR) and the active warm displacer (AWD) in an 8 K Stirling-type pulse tube cryocooler. Through numerical simulation methods, the influence of structural parameters of the cold ITR and operating parameters of AWD on acoustic power and impedance was studied. The results indicate that the length and diameter of the inertance tube, as well as the displacement and phase of the AWD, will affect the distribution of PV power inside the middle heat exchanger. The impedance distribution inside the pulse tubes of the higher-temperature section and the lower-temperature section changes in opposite directions. Through experiment, the effectiveness of the cold ITR and the adjustment function of the AWD were verified. A cooling capacity of 74 mW at 8 K can be obtained with the electric power of 177.5 W and a precooling capacity of 9.1 W/70 K. The AWD has a significant adjustment effect on T1 and T2, reaching the lowest no-load temperature at 2.13 mm and 48°, respectively, with a minimum no-load temperature of 5.13 K.