Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : December 02, 2023
Sumitomo Heavy Industries, Ltd. (SHI) has been supplying 1-stage and 2-stage Stirling cryocoolers and J-T cryocoolers as cooling systems for earth observation satellites and scientific satellites for sensor cooling and shield cooling applications. The performance of the 2-stage Stirling cryocooler used as a pre-cooler for the J-T cryocooler has a cooling capacity of 0.2 W at 20 K/1 W at 100 K at a maximum electrical input power of 90 W [1]. In the future, it is planned to increase the size of the sensor to improve the observation capability, which will require an increase in the cooling capacity of the cryocoolers. Furthermore, measures to reduce vibration to the sensor are necessary, and in the case of the Stirling cryocooler, a driver is also installed in the expander to actively control vibration to achieve low vibration. Currently, SHI is using 1-stage Stirling cryocooler as a pre-cooler for a 2-stage Stirling cryocooler to increase cooling capacity and improve system efficiency by operating each cryocooler at a specialized frequency for 80 K and 15 K, the pre-cooling temperature of the J-T cryocooler. However, a total of six drivers are required for low-vibration cryocoolers and the heat bridges used for conduction cooling of the 1-stage and 2-stage Stirling cryocoolers have a large heat transfer loss to make them rigid enough not to load the cylinder of the expander, which increases the temperature of the cold head and reduces cooling efficiency. Furthermore, there is a need to extend the life of cryocoolers from the current 5 years to 10 years, and the 1-stage Stirling cryocoolers and J-T cryocoolers are on track to have a 10year life based on the knowledge obtained from past tests. However, for the 2-stage Stirling cryocooler, it is difficult to maintain the clearance seal of the 2-stage displacer and achieving a 10-year life is a tough challenge. To solve the vibration and life issues, we have been considering the use of a pulse tube expander without moving parts in the expander.
This paper describes the results of performance tests using a previously developed 1-stage pulse tube cryocooler with a cooling capacity of 5 W at 77 K as a pre-cooler (Figure 2) and a 2-stage PT expander designed and fabricated using a compressor for a 2-stage Stirling cryocooler.
