PERFORMANCE LIMITS OF PULSE TUBE CRYOCOOLERS USING [sup 3]HE

Abstract

The enthalpy, entropy, and exergy flows resulting from the real gas effects of 3 He in ideal pulse tube cryocoolers are described. The discussion follows a previous description of the real gas effects of 4 He in ideal pulse tube cryocoolers and makes use of a recently developed model of the thermophysical properties of 3 He. This model is used to describe how the thermodynamic flows are affected by real gas phenomena of 3 He and compares these effects to similar effects for 4 He. The analysis was done over the pressure range 0.3-2 MPa and temperatures down to 1 K. At 2 MPa there is almost no difference in the cooling power between 3 He and 4 He. At lower pressures, using 3 He is advantageous. There is a 1-2 K reduction in the 3 He cooling power vs. temperature curves compared to those for 4 He in the 0.3-1 MPa range.

Ultimate Temperature of Pulse Tube Cryocoolers

“…The approach has been previously described for ideal and non-ideal pulse tubes [8][9], for 4 He real gas effects in ideal pulse tube cryocoolers [1], and for 3 He real gas effects in ideal pulse tube cryocoolers [5].…”

“…The performance is significantly reduced for temperatures near and below the critical temperature of the working fluid. This was shown analytically for 4 He [2-3] and 3 He [5]. Since the critical point of 3 He occurs at a lower temperature than for 4 He, pulse tube coolers using 3 He reach lower temperatures than those using 4 He.…”

“…It is capable of cooling to any temperature. When real gasses are used, the performance of pulse tube cryocoolers is affected at all temperatures [2][3][4][5][6]. The performance is significantly reduced for temperatures near and below the critical temperature of the working fluid.…”