Comparative study of four displacer phase-shifters in a split pulse tube refrigerator working at 170 K

Abstract

A pulse tube refrigerator (PTR) with a displacer phase-shifter has great potential for realizing high-efficiency PTRs. There are four types of displacer phase-shifters: passive rod displacer, passive rodless displacer, active rod displacer, and active rodless displacer. However, determining the displacer-type PTR with the greatest potential in engineering applications remains a challenge. Combined with response surface methodology, one-dimensional numerical simulations were conducted to address this problem. Energy efficiencies were compared at a cooling capacity of 50 W at 170 K. The piston-displacer phasor diagram, displacer force analysis, and key parameter distribution were used to explain the differences in performance. The phase-shifters were ranked from superior to inferior in terms of the relative Carnot efficiency based on the shaft power as follows: 24.2 % for the passive rod displacer, 23.8 % for the active rod displacer, 21.5 % for the active rodless displacer, 19.9 % for the inertance tube, and 13.3 % for the passive rodless displacer. The passive rodless displacer was unsuitable in the split structure with long connecting tubes because it failed to provide the ideal phase relation. The merit analysis of different displacer-type PTRs showed that the PTR with the passive rod displacer had the greatest potential for engineering applications. The relative Carnot efficiency was enhanced to 25.3 % by removing the hot heat exchanger, shortening the connecting tube, and changing the locations of the T-junction and phase-shifter. This study compared the four types of displacer phase-shifters simultaneously, which is scarce in the literature on PTRs. Moreover, it presents an effective approach to achieve a high-efficiency displacer-type PTR based on an existing inertance-tube-type PTR.