Effect of Regenerator Entrance Shape on Performance of Compact Pulse Tube Cryocooler

Pulse tube cryocoolers are more attractive than other small cryocoolers because they have no moving parts in the expander and thus have higher reliability. However, Stirling type pulse tube cryocooler needs further improvement on regenerator. The entrance areas at the regenerator ends of the typical pulse tube cryocooler are smaller than the cross-sectional area of the regenerator matrix. So, the working gas flow in the regenerator has non-uniform velocity distribution with the expansion and contraction flow. They cause the excessive pressure loss and reheat loss. In this study, the effect of the regenerator entrance shape on the performance of compact pulse tube cryocooler was examined experimentally. Additionally, the analytical method for losses in the regenerator using experimental data is suggested. Experimentally and analytically, the effect of after-cooler end at the regenrator has been bigger than that of cold-head end.