Methane Liquefaction with an Active Magnetic Regenerative Refrigerator

This manuscript reports liquefaction of methane using an active magnetic regenerative refrigerator (AMRR) which cooled from 285 K to 135 K. This refrigerator has two identical regenerators fabricated with adjacent layers of four ferromagnetic refrigerants, each with sequentially lower Curie temperatures and lesser masses from hot to cold temperatures. The refrigerants either heated or cooled by the magnetocaloric effect when moved in or out of a high-field superconducting magnet. The dual multilayer regenerators were assembled in opposition with a common cold region between them. The same mass of helium heat transfer gas was circulated through all layers of the regenerators during the two flow steps of the four-step AMR cycle. A compact coil-fin tube heat exchanger closely fitted around a small liquid storage vessel mounted in the cold region of the assembly was alternatively cooled by cold 2.76 MPa helium gas during hot-to-cold flow steps of the AMRR cycle. In this experiment the cold coil-fin tube heat exchanger was used to cool and liquefy a process stream of methane gas supplied at 295 K from a lecture bottle at different pressures in different runs. By measuring time to liquefy a known volume of methane at three different pressures, cooling powers of the AMRR as a function of temperature were determined. The resultant data were compared to values predicted by the cooling power equation of the AMRR model. Conclu-sions from these experiments and suggestions for future work are presented.