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Description
Due to the absence of moving parts at cold end, Stirling type pulse tube cryocoolers (SPTCs) possess the benefits of low vibration, long maintenance intervals and high reliability. SPTCs have been widely used in the fields of superconductors, aerospace, industrial gas liquefaction etc.
Currently, single-stage SPTCs operating at liquid nitrogen temperatures have been successfully developed and commercialized. However, the development of highly efficient and reliable multi-stage SPTCs for space applications operating below 20K is still ongoing.
The novel concept of the shared inertance tube SPTC has been developed. In this structure, a multi-stage refrigeration system is driven by a step piston compressor, with the shared inertance tube connecting the hot ends of the pulse tubes. This structure enables the redistribution of work at the hot end of the pulse tube, thereby enhancing the refrigeration capacity of the low-temperature stage and ultimately improving the overall efficiency of the multi-stage SPTC.
Before conducting research on the 2-stage shared inertance tube SPTC, numerical and experimental investigations will be carried out on a single-stage shared inertance tube SPTC with two cold heads in this paper.
In the single-stage shared inertance tube SPTC, two identical cold heads are driven by two identical compressors. A mutual inertance tube connects two same cold heads at the hot ends of the pulse tube. The cold head consists of the aftercooler, the regenerator, the cold heat exchanger, the distributor, and the pulse tube. Fluids in both cold heads flow into a mutual inertance tube to get phase shift. The impedance of two cold heads is the same，so in ideal condition, at the hot end of the pulse tubes, phase angle, pressure amplitude and mass flow rate should be the same.
A comparison is made between a single-stage SPTC with a single cold head utilizing an inertance tube and a shared inertance tube SPTC with double cold heads utilizing an inertance tube whose cross area is doubled. Under the same operating conditions, the phase-shifting angle at the inlet of the inertance tube increases with the diameter of the tube according to thermoacoustic theory. When using an inertance tube to connect two identical cold heads, if helium flows from the inertance tube into the hot end of the pulse tube, the mass flow rate is halved. However, the phase angle at the hot end of the cold head pulse tube remains unchanged from that at the inlet of the inertance tube. Therefore, using a shared inertance tube instead of two separate inertance tubes can achieve greater phase-shifting capability, especially in situations where the cooling capacity is limited and the inertance tube phase-shifting capability is poor. The numerical simulation results are presented, which are consistent with the findings of the thermoacoustic analysis. The inertance tube in the shared inertance tube SPTC has larger phase shift ability than that in a single-stage SPTC with a single cold head.
Preliminary experiments is conducting to verify the feasibility of the shared inertance tube pulse tube refrigerator.
Acknowledgment
This work was supported by the National Natural Science Foundation of China (No.52076151) and National Key Research and Development Program of China (No.2022YFB4002802).
| Submitters Country | China |
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