2020 Volume 55 Issue 1 Pages 53-58
A new Active Magnetic Regenerator (AMR) cycle has been proposed and tested. We developed a four-unit AMR (fAMR) driving cycle consisting of four AMR units and two magnets. f-AMR operates a pair of magnetization and demagnetization processes in an AMR cycle simultaneously, and as a result, four AMR cycles can be continuously operated. The merits of the fAMR cycle are: four times larger cooling capacity, reducing the thermal loss of heat transfer fluid, a simple mechanism to provide a larger temperature span, feasibility as a thermal device, and expandability of the AMR unit number. Experimental results at room temperatures showed unique properties of f-AMR. Using a weak 0.75 T permanent magnet, the largest temperature span reached to 20 deg. using Gd spheres with a 0.4 mm diameter and COP was larger than 1.0 for a temperature span of 10 deg. We have started to use the f-AMR cycle for a hydrogen re-condensation system at 20 K. A hybrid cooling system using f-AMR and GM cycles will be able to pursue a target of 15% Carnot for hydrogen re-condensation liquefiers.
