A three-stage Stirling pulse tube cryocooler operating below the critical point of helium-4

Experimental Investigation on Regenerator Materials of Stirling-type Pulse-tube Refrigerator Working at 20K

“…Stirling-type PTR (STPTR) is driven by no-valve compressor with a relatively high frequency. Nowadays, Stirling-type PTR can reach a temperature below liquid helium and distinguish itself in many fields such as optical detection for its superiority in small size, light weight, and high stability Olson et al (2003), Olson et al (2006), Nguyen et al (2007), Nast et al (2007), Qiu et al (2011), Bradley et al (2011).…”

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

“…At present the efficiency of 4 K SPTC is still rather low (about 0.5-1% Carnot efficiency) [11][12][13][14][15][16]. The losses in the regenerator for a 4 K SPTC, given by the time-averaged enthalpy flux, increase rapidly due to the low heat capacity of regenerator materials near 4 K and the real gas properties of helium at this low temperatures [17].…”

“…In addition, high operating frequencies yield smaller thermal penetration depth of helium which makes the heat transfer worse [18]. As a result, a SPTC usually employs a multi-stage (three-stage or four-stage) structure to precool the final stage to reach 4 K [11][12][13]16]. The design of a multi-stage regenerator is very complicated due to a large number of operating and structure parameters for each stage of the regenerator.…”

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

“…Compared with the relatively matured 80 K SPTCs, the efficiency of 4 K SPTCs is still rather low (about 0.5%-1% Carnot efficiency) (Olson et al, 2006;Nast et al, 2007;Bradley et al, 2008;Radebaugh et al, 2008;Qiu et al, 2011) due to regenerator losses with both the 4 K low temperature region (van Sciver, 1986) and high operating frequencies (Tanaeva et al, 2006). At temperatures below about 15 K, the specific heat capacity of regenerator materials significantly decreases with the cube of the temperature, while the specific heat capacity of helium-4 (He-4) increases remarkably, which leads to large regenerator heat transfer loss.…”

“…In addition, the high operating frequency yields smaller thermal penetration depth of helium, which makes the heat transfer between the matrix and helium worse. SPTC usually adopts a three-or even a four-stage regenerator structure to precool the final stage regenerator to reach the 4 K temperature region (Olson et al, 2006;Nast et al, 2007;Qiu et al, 2011). The number of the regenerator stages is influenced by both the performance of the final stage regenerator and the precooling capacity of the previous stage regenerators working at warmer temperature regions (typically above 80 K).…”