Improvement of room temperature magnetic refrigerator using air as heat transfer fluid

In order to elucidate the cooling characteristics and to improve the cooling performance of a room temperature magnetic refrigerator using air as a heat transfer fluid, experimental and analytical study concerned with the heat transfer characteristics of an active magnetic regenerator (AMR) are conducted. The basic components of the target system are a magnetic circuit, a test section, a fluid supplying system and an associated instrumentation. Spherical gadolinium particles are packed in the test section as a magnetic working substance. Temperature profiles under several operating conditions for the Air-AMR are measured and calculated. Also, those for the Water-AMR are investigated in order to compare with the Air-AMR. The results show that the AMR cycle is very effective for improvement of the cooling performance of a room-temperature magnetic refrigerator for both heat transfer fluids, because increase in the temperature span between the hot-end and the cold-end due to regeneration is realized. Furthermore, it is revealed that a high flow rate of air is necessary in order to improve the cooling performance of the Air-AMR refrigerator, compared with the case of the Water-AMR. It is also shown that thermophysical properties of the heat transfer fluid have a significant effect on the cooling characteristics of an AMR refrigerator.