Investigation on the cool-down speed of Stirling type pulse tube cryocooler with inertance tube

In some applications, the cool-down speed obtainable with a cryocooler is important besides the high efficiency at the working temperature. Because of the difference in configurations, the design and the control strategies for various cryocoolers may be different. This work numerically studies the cool-down characteristics of a Stirling-type pulse tube cryocooler (PTC), which uses inertance tube and reservoir as the phase shifter and work at the temperature region of liquid nitrogen. The cryocooler is predicted to provide a nominal cooling power of 18.7 W at 77 K. Three cool-down strategies, namely, cool-down with constant voltage at 66 Hz, cool-down with constant piston displacement by tuning the voltage at 66 Hz, and cool-down with constant piston displacement by tuning voltage and frequency simultaneously during the cool-down process, are investigated. The corresponding calculated cool-down time from the ambient temperature to 77 K of these strategies are 340, 275, and 260 s, respectively. Using the third strategy, the cool-down time can be reduced by 23%.