Experimental investigation of hybrid system of pulse tube with active magnetic regenerator (AMR)

Abstract

This paper investigates a hybrid system, which replaces passive regenerator in the pulse tube refrigerator by active magnetic regenerator (AMR). The system is mainly composed of an AMR (which makes cooling effect by magnetocaloric effect), an HTS magnet (which produces magnetic field change) and a pulse tube (which creates cooling effect by gas expansion). The AMR is composed of two different magnetic materials (GdNi2, Dy0.85Er0.15Al2) and surrounded by the HTS magnet. The AC operated HTS magnet is cooled by a two-stage Gifford-McMahon (GM) cryocooler and generates 0 to 1 T magnetic field change to AMR with 0.5 T/s ramping speed. Helium gas is used as heat transfer fluid and its oscillating flow is achieved by a helium compressor and two solenoid valves. Two experimental cases, passive regenerator experiment (magnet off) and active regenerator experiment (magnet on) are conducted and compared. As a result, the cold end temperature of the pulse tube records 59.9 K and 58.2 K respectively when the system’s warm end temperature is set to 65 K. The paper discusses several ineffective factors that degrade the performance of the experimental apparatus.