Active Magnetic Regeneration - Magnetocaloric Energy Conversion: From Theory to Applications - page 128

Fig. 4.17 The temperature span at zero cooling power as a function of the utilization factor for
different operating frequencies in the case of a packed-bed AMR with Gd spheres of 0.5 mm for a
1 T magnetic eld change

Fig. 4.18 The cooling power at 15 K of temperature span as a function of the utilization factor for
different operating frequencies in the case of a packed-bed AMR with Gd spheres of 0.5 mm for a
1 T magnetic eld change

1
2 s mag þ

m ¼ ð 4 : 27 Þ

2 s f

where s mag is the duration of the magnetization and demagnetization process ((de)
magnetization time) and s f is the duration of the

fl uid fl ow period. Here, we assume

that both ow periods as well as both the magnetization and demagnetization

times are equal (symmetrical operation of regenerator), which is usually the case in
an AMR cycle. Since the thermodynamic cycle of the AMR process contains two
relatively different types of processes: (de)magnetization and

fl uid fl

ow period, the
impact of the operating frequency of such a cycle must therefore be more carefully
analysed. The (de)magnetization process should be as short as possible, regardless
of the duration of the

fl uid fl

fl uid fl ow period and the performed AMR cycle, since a long