Comparison study of three displacer type phase shifters in a two-stage Stirling type pulse tube refrigerator working around liquid hydrogen temperature

Abstract

With growing demand of high efficiency and compact cooling systems for the applications of space detectors, superconductivity and infrared detectors, pulse tube refrigerator (PTR) shows great promise. Ambient displacer phase shifter (AM-D) has gained popularity due to its compactness and recovering acoustic power. While achieving satisfied phase relationship and cooling efficiency remains challenging in multi-stage PTR operating below 20 K. Thus, cold displacer (CO-D) and thermal gradient displacer (TR-D) are proposed in this paper, which relocates the lower-stage displacer from ambient temperature to the upper-stage cold end. This could improve the phase shift ability and reduce the exergy losses in lower stage pulse tube. Theoretical analyses are first performed on phase shifting mechanism of three type displacer phase shifters. Following that, simulations are carried out to investigate the influence of displacer parameters, including compliance volumes, moving mass, spring stiffness and mechanical damper. Results indicate that PTR using CO-D or TR-D can achieve a cooling capacity of around 2.3 W, representing a 35 % increase over AM-D. Axial variations of phase relationship and acoustic power are compared, exergy losses and dual-temperature cooling capacities are then investigated. CO-D and TR-D phase shifters demonstrate the potential of attaining higher efficiency at liquid hydrogen temperature.