Pulse tube refrigerators are widely used in space detection and quantum computing due to their low vibration output at the cold end and high reliability. Dual-temperature-zone pulse tube refrigerators can simultaneously achieve dual cooling temperatures. However, in the actual application scenario, the cooling performance is largely affected by the ambient temperature zones, which limits applications in complex environments. In this study, based on the dual-temperature-zone pulse tube refrigerator with an active acoustic power recovery phase shifter, the influence characteristics of the ambient temperature on the gas spring of the phase shifter, inlet acoustic power of the cold finger, and dual-temperature cooling capacities are investigated. Unlike the conventional piston-type phase shifter, which has only an expansion chamber, the acoustic power recovery phase shifter has an acoustic power recovery chamber at the back end of the piston, which can recover the expansion acoustic power from the hot end of the pulse tube. Compared to the traditional piston-type phase regulator containing only an expansion chamber, when the ambient temperature increases from 253 K to 333 K, the maximum change in the total gas spring stiffness of the piston in the acoustic power recovery phase shifter is only 2630 kg/s², and the level of impact could be reduced by 86.1%, which shows that the acoustic power recovery phase shifter has a higher adaptability to the ambient temperature. The experiment shows active control of cooling capacities in dual-temperature zones by adjusting the piston motion of the phase shifter at ambient temperatures of 253 K and 333 K.

Helium throttling refrigeration technology is a key cooling method used in liquid helium temperature zones in space. Research on the rapid cooling of chillers coupled with large heat capacity loads is important for the efficient operation of large heat capacity loads. To clarify the cooling characteristics of helium throttling chillers under different rapid cooling schemes, cooling experiments with no additional measures scheme, room-temperature valve bypass scheme, and thermal switch scheme were conducted based on GM pre-cooled helium Joule-Thomson chillers under different heat capacity loads. The experimental results show that the load-free pull-down times of the three schemes were 39.8 h, 20.5 h, and 19 h, respectively. Based on thermodynamics and heat transfer theories, the changes in the radiation, convection, heat conduction, and throttling source terms during no-load cooling were quantitatively analyzed, and the reasons for the difference in cooling time of helium throttling chillers under different schemes were explained. With a simulated load of 0.136 kg of copper, schemes of the room-temperature valve bypass and hot switch were adopted, and the corresponding cooling times were 25.5 h and 20 h, respectively. The experimental results show that the cooling effects of the thermal switch and room-temperature valve bypass scheme are essentially the same for the cooling of a small heat capacity load. Therefore, thermal switch cooling has significant advantages for large-heat-capacity load cooling.

A compressor outlet tube is a transmission component of sound power, and its sound power loss directly affects the performance of pulse tube cryocoolers. Flexible bellows can adjust the relative positions of compressors and cold fingers in applications compared with traditional rigid smooth tubes. This study analyzed the flow characteristics of two types of connected pipes by simulation, and the influence of different types of connected pipes on the performance of the entire machine was verified experimentally to determine the influence of flexible bellows on the cryocooler. The simulation results demonstrated that mixed flow appears at the ripple of the bellows, resulting in greater resistance loss, when compared with a rigid smooth pipe. Under the same inlet parameters, the outlet mass flow and pressure amplitude were lower, and the sound power loss was greater. The experimental results demonstrated that the input power required by the bellows was higher when the cooling capacity was the same. When the cooling temperature was 37.5 K and the cooling capacity was 0.5 Wthe input power of bellows and smooth tubes was 119 W and 112 W, respectively; when the cooling capacity was 3.0 W, the input power of bellows and smooth tubes was 279 W and 259 W, respectively.