Shigeki Hirano

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.

Cooling Characteristics of Regenerative Magnetic Refrigeration With Particle-Packed Bed

The aim of our study was to elucidate the fundamental cooling characteristics and to improve the cooling characteristics of a room-temperature magnetic refrigerator operated under an active magnetic regenerator (AMR) cycle. The AMR refrigeration cycle, which includes a thermal storage process and a regeneration process, is used to realize a practical magnetic refrigerator operating near room-temperature. The basic components of the target AMR system are a magnetic circuit, test section, fluid-displacing device, and associated instrumentation. Spherical gadolinium particles are packed in the test section as the magnetic working substance, and air and water are used as heat transfer fluids. The cooling characteristics of the target AMR system under various operating conditions are investigated. The results show that the AMR cycle is very effective in improving the cooling performance of the room-temperature magnetic refrigerator.