Performance of a precooled 4 K Stirling type high frequency pulse tube cryocooler with Gd2O2S

Abstract

Abstract:The efficiency of 4 K Stirling type pulse tube cryocoolers (SPTCs) is rather low due to significant regenerator losses associated with the unique properties of helium around 4 K and the high operating frequencies. In this paper, regenerator performance at liquid helium temperature regions under high frequencies is investigated based on a single-stage SPTC precooled by a two-stage Gifford-McMahon type pulse tube cryocooler (GMPTC). The 4 K SPTC used a 10 K cold inertance tube as phase shifters for better phase relationship between pressure and mass flow. The effect of the operating parameters, including frequency and average pressure on the performance of the 4 K SPTC, was investigated and the first and second precooling powers provided by the GMPTC were obtained. To reduce the regenerator heat transfer losses, a multi-layer regenerator matrix, including Gd 2 O 2 S (GOS) and HoCu 2 , was used instead of a single-layer HoCu 2 around 4 K. A theoretical and experimental comparison between the two types of regenerator materials was made and the precooling requirements for a regenerator operating at high frequencies to reach liquid helium temperatures were given, which provided guidance for the design of a three-stage SPTC.

Effects of cold‐end temperature and heat load on the cooling characteristics of a pulse tube refrigerator

“…However, for a heat load of less than 900 W, the relative Carnot efficiency exceeded 20%. The same trend occurred at a cold‐end temperature of 100 K. To meet the requirements of varying heat load at different cold‐end temperatures, many PTRs were developed for different capacities …”

“…The same trend occurred at a cold-end temperature of 100 K. To meet the requirements of varying heat load at different cold-end temperatures, many PTRs were developed for different capacities. [9][10][11][12] For changing parameters at the cold end (cold-end temperature and heat load), the operational behavior of a PTR varies from the optimal working conditions. Based on enthalpy phase modulation theory, Radebaugh discussed the effects of the mass flow, pressure wave, and phase angles at the cold end on the cooling performance of PTRs.…”

Influence of regenerator void volume on performance of a precooled 4 K Stirling type pulse tube cryocooler

“…e l s e v i e r . c o m / l o c a t e / c r y o g e n i c s matrix near 4 K [21]. In this paper influence of regenerator void volume on the performance of the 4 K SPTC is investigated theoretically and experimentally.…”

“…The main reason may be that as the average pressure decreases the specific heat capacity of helium-4 near 4 K increases significantly. When the average pressure is 0.5 MPa, the specific heat capacity of helium-4 reaches a maximum value of 0.9 J/K cm 3 at 6 K while the specific heat capacity of regenerator material HoCu 2 is only 0.38 J/K cm 3 [21]. The specific heat capacity ratio of regenerator matrix to helium is seriously degraded leading to severe regenerator heat transfer losses.…”

Temperature inhomogeneity in high capacity pulse tube cryocoolers

“…Stirling type pulse tube cryocoolers (SPTC), having the benefit of no moving parts at the cold end, could be more reliable and require lower maintenance than Gifford-McMahon (GM) and Stirling cryocoolers (Li et al, 2014;Zhang et al, 2014). However, there are still serious unsolved problems in large scale SPTC.…”