**3.7 Canadian system**

236 Trends in Electromagnetism – From Fundamentals to Applications

(b) Fig. 7. The Japanese Device: (a) The initial one, (b) The improved one (Hirano et al., 2007;

The ACM (Astronautics Corporation in Madison) has led many researches on magnetic refrigeration and achieved several patents in this field (Engelbrecht, 2005). In this corporation, an AMRR system was designed; it consists of a wheel with 6-bed regenerators composed of gadolinium powder. This wheel is rotating inside an area of high magnetic field of 1.5 T. The regenerative beds exchange with the fluid. The flow of the fluid is adjusted according to the relative position of each bed inside the magnetic field. Fig. 8

For cycles rotating with a frequency varying from 0.16 to 2 Hz and water rate flows varying from 0.4 to 0.8 l/min, the temperature spans obtained between the heat source and the cold

source are from 4 to 20°C and the cooling power values are from 50 to 100W.

Okamura et al., 2006, 2007).

**3.6 The magnetic system of Zimm** 

shows the photography of this prototype.

Fig. 8. ACM prototype (Zimm, 2002).

At the University of Victoria in Canada, Tura and Rowe (2007) constructed a magnetic refrigerator containing permanent magnets for a testing of all sorts of magnetic refrigerants in different configurations. This machine is shown in Fig. 9. A nested Halbach array of NbFeB permanent magnets was applied and led to a magnetic field of 0.1-1.47 T strength. Water was the heat transfer fluid with a heat rejection temperature range of 253-311 K, and the operation frequency was between 0 Hz and 4 Hz. The prototype showed cylindrical magnetocaloric regenerators (with a porosity of 57%) whose volume, diameter and length were 20 cm3, 16 mm, and 110 mm, respectively. The void in the regenerator of the hot heat exchanger and the cold heat exchanger was 0.83 cm3 and 0.4 cm3, and the parallel flow paths in the heat exchangers were optimized with a computational fluid dynamics (CFD) approach. The system which is designed to be flexible showed many advantages: for example, a simple design, easy accessibility to all the components and very low heat leakages. This machine reached a maximum temperature span of 13.2 K (Yu, 2010).

Fig. 9. Rotary magnetic refrigerator with permanent magnets as presented by researchers of the University of Victoria in Canada (Tura and Rowe, 2007).
