Design of a 30K Single-Stage Free-Piston Stirling Cryocooler

Free-piston Stirling cryocooler (FPSC) is promising in cooling down electronic and high temperature superconducting (HTS) devices. Currently, most of the FPSCs work around 77 K due to their watts of cooling power at 30 K has been designed and tested by our group and the preliminary results showed positive prospect. In order to maintain the advantage of simplicity, in this work a single-stage a cooling power of 350 W at 80 K. In order to obtain a lower cooling temperature, a variable diameter regenerator is adopted in the new cryocooler. Besides, different combinations of phase shifters are that the cryocooler can reach a no-load temperature of 24.61 K and a cooling power of about 51 W at 30K obtained simultaneously with an input acoustic power of about 3.27 kW, corresponding to a performance dependences on the operating conditions are studied in detail. INTRODUCTION In recent years, for the purpose of cooling high temperature superconducting (HTS) devices (such as transformers, generators or motors, etc.), the need for cryocoolers with tens of watts of cooling capacity in the range of 20–30 K has been rapidly increasing1,2,3. Currently, the Giffordthe cooling requirements in this temperature region and are commercially available4. However, the cryocooler is reduced by the irreversible loss due to the rotary valve. In recent decades, advances in Stirling-type pulse tube cryocooler research have brought about another alternative way to provide limited cooling power in the 30 K region5. The Stirling-type pulse tube cryocoolers possesses the achieved was usually low resulting from the dissipation of the expansion power. Cryocoolers 20, edited by S.D. Miller, R.G. Ross, Jr. and J.R. Raab ©¶International Cryocooler Conference, Inc., Boulder, CO, 2018 41 and free piston type from the perspective of transmission. In the traditional kinematic Stirling cryocooler, displacer and power piston are rigidly connected via a mechanical linkage. The inevitable existence of oil-lubrication and a dynamic seal in kinematic Stirling cryocooler requires frequent maintenance. In contrast, in the FPSC, the displacer and the power piston are free and acoustically architecture is generally needed in FPSCs. Currently, two-stage FPSC with small cooling capacity 7,8. In order to meet the requirement of the HTS applications, most recently, a two-stage FPSC aiming at providing tens of watt cooling power at 30 K has been designed and tested by our group9. The preliminary results showed that a lowest cold-head temperature of 27.6 K and a cooling power of tion which can achieve similar results is proposed on the basis of a single-stage FPSC which could 10. This paper introduces the design of a single-stage FPSC, which aims at providing tens of watts designed cryocooler is presented and the operating parameters’ sensitivity effect on the cooling performance are studied. Finally, conclusions are drawn. DESIGN APPROACH AND SYSTEM CONFIGURATION The design goal for the FPSC is to provide a cooling power of 50 W at a temperature of 30 K mercially available software SageTM is used for numerical calculations. The mean operating pressure shifter, the porosity, length and equivalent housing diameter of the cold end segment regenerator Figure 1 illustrates a schematic of the new designed single-stage FPSC prototype, which is designed based on a developed FPSC with large cooling capacity at the liquid nitrogen temperature Figure 1. Schematic of the new designed single-stage FPSC prototype. 42 CRYOCOOLERS FOR 4-40 K APPLICATIONS