Study on the Influence of Precooling and Intermediate Temperature on the Performance of an 8 K Multi-stage Pulse Tube Cryocooler

Stirling-type multi-stage pulse tube cryocoolers operating at 8 K possess obvious advantages in space exploration applications such as terahertz detection. For Stirling-type pulse tube cryocoolers, the appropriate regenerator temperature distribution exerts a significant influence on cooling performance. Because the change of temperature distribution will affect the exergy loss in the regenerator. In this paper, systematic theoretical and experimental studies on the effect of regenerator temperature distribution on the performance of an 8 K pulse tube cryocooler were conducted. Simulation results indicate that: when the temperature of the intermediate heat exchanger （T₁） remains constant, the exergy loss in the high-temperature section regenerator （REG1） increases with the rise of the precooling temperature （T_pre）, when the precooling temperature increases from 63 K to 78 K, the total exergy loss in REG1 rises from 37.91 W to 42.25 W, while the exergy loss in the low-temperature section regenerator （REG2） remains basically unchanged; when T_pre is constant, an increase in T₁ leads to a decrease in exergy loss in REG1, but an increase in exergy loss in REG2. Meanwhile, as T₁ increases, both the amplitude and phase of the impedance at the hot end of Pulse Tube 2 （PT2） decrease. Changes in exergy loss within the regenerator can affect cooling performance. Experimental results show that when T_pre increases, the cooling capacity obtainable at the intermediate heat exchanger （Q₁）decreases, When the precooling temperature increases from 63.2 K to 73.5 K, Q₁ decreases from 0.56 W to 0.19 W, while the cooling capacity obtainable at the cold-end heat exchanger（Q₂） remains basically unchanged; when T₁ increases, Q₁ increases while Q₂ decreases. When T₀ is 70 K and T₁ is 23.35 K, the cryocooler can achieve a cooling capacity of 74 mW at 8 K （with an input power of 349.5 W）.