**3.6 The magnetic system of Zimm**

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 shows the photography of this prototype.

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.

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