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Description
Multi-stage pulse tube cooler normally uses U-type configuration. For compactness, it is attractive to build a completely co-axial multi-stage pulse tube cooler. In this way, annular shape pulse tube is inevitable. Although there are a few reports about annular pulse tube used in a cooler system, a detailed study and comparison with a circular pulse tube is lacking. In this paper, a numeric model based on CFD software is firstly carried out to compare the annular pulse tube and circular pulse tube used in a single stage in-line type pulse tube cooler with about 10 W cooling power at 77 K. The length and cross sectional area of the two pulse tubes are kept the same. The simulation results show that enthalpy flow in annular pulse tube is lower by 1.6 W (about 11% of the enthalpy flow) than that in circular pulse tube. Flow and temperature distribution characteristics are also analyzed in detail. Experiments are then conducted for comparison on an in-line type pulse tube cooler. With the same acoustic power input, the pulse tube cooler with a circular pulse tube obtains 7.88 W cooling power at 77 K, while using annular pulse tube leads to a cooling power of 7.01 W, a decrease of 0.9 W (11.4%) on the cooling performance. The study sets the basis for building a completely co-axial two-stage pulse tube cooler.