Experiments on the thermodynamic performance of a 'u-tube' pulse tube expander

摘要

As has been extensively discussed in the literature, pulse tube cryocoolers have numerous advantages over other closed-cycle coolers which arise from the absence of moving parts in the pulse tube expander. Advantages in the areas of cost and reliability are of interest to the user community in general, and the additional advantage of cold-tip vibration minimization is of particular importance for cooling applications in electrooptical (E-O) systems for it leads to unique system integration advantages. For example, the low vibration of the expander may make it possible to mount the focal plane directly on the cold tip, eliminating the thermal strap required when using other types of expanders. The `U-Tube' configuration is particularly convenient from the standpoint of system integration because the cold region extends as a tip from a single warm end heat exchanger, unlike the linear pulse tube (LPT) in which the cold region is bounded on either side by warm regions of the expander. A U-Tube expander was recently constructed and tested, and the thermodynamic effieiency was seen to be comparable to that of the LPT deisgn. At an operating temperature of 77K, a cooling capacity of 2.9 W was measured for an input P-V power of 84 W. The expander design and experimental data are discussed.