Suchergebnisse

We present the performance of an active magnetic regenerator prototype with a multi-bed concept and parallel flow circuit. The prototype applies a two-pole permanent magnet (maximum magnetic flux density of 1.44 T) that rotates over 13 tapered regenerator beds mounted on a laminated iron yoke ring. Each bed is filled with about 262 g of spherical particles, distributed in layers of ten alloys of La(Fe,Mn,Si)13Hy (CALORIVAC HS) with different Curie temperatures. Other important features are the solenoid valves, the monitoring of the temperatures exiting each bed at the cold side, and a torque meter used to measure the magnetic power required to drive the cycle. The opening behavior of the solenoid valves (i.e., the blow fraction) could be adjusted to correct flow imbalances in each bed. The device provided a maximum cooling power of about 815 W at a cycle frequency of 1.2 Hz, a utilization of 0.36, and a hot reservoir temperature of 295 K while maintaining a 5.6 K-temperature span with a coefficient of performance of 6.0. In this case, the second-law efficiency was 11.6%. The maximum second-law efficiency of 20.5%, which represents one of the largest for a magnetocaloric device, was obtained at a cycle frequency of 0.5 Hz, a utilization of 0.34, and a hot reservoir temperature of 295 K at a temperature span of 10.3 K. Under these conditions, the device absorbed a cooling load of 288 W with a coefficient of performance of 5.7. It was also shown that an unbalanced flow due to different hydraulic resistance through the beds can cause cold side outlet temperature variations, which reduce the system performance, demonstrating the importance of a well-functioning, balanced flow system. ; This work was in part financed by the RES4Build project, which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 814865. We would like to acknowledge the ENOVHEAT project funded by the Innovation Fund Denmark (contract no 12-132673). We also wish to acknowledge Mike ...

The design of a rotary active magnetic regenerator heat pump device with a multi-bed concept is presented. Important design features are the rotating two-pole magnet assembly, the laminated iron ring, the 13 fixed tapered regenerator beds, and the dynamically adjustable parallel flow circuit. The optimized magnet design was developed with optimally shaped segments and optimum remanence for the desired magnetic field distribution oscillating between 0 and 1.44 T in the air gap. The iron ring was laminated to reduce the eddy currents, allowing the device to run at cycle frequencies up to 3 Hz. The design of the regenerator housing was optimized with respect to parasitic losses and even flow distribution in both directions. Employing 3.4 kg of La(Fe,Mn,Si)13Hy (CALORIVAC HS) refrigerant and at a hot reservoir temperature of 295 K and a cycle frequency of 0.5 Hz, the heat pump achieved a maximum second-law efficiency of 20.6 %, while providing a heating load of 340 W with a heating COP of 6.7 at a 10.3 K span. The COP values presented only consider the magnetic power and ideal pump power delivered to the AMR, neglecting the pump efficiency. At 1.2 Hz, the device produced a maximum heating power of 950 W while maintaining a 5.6 K span, resulting in a heating coefficient of performance and second-law efficiency of 7.0 and 11.6 %, respectively. The performance demonstrated in this paper could be an important milestone in the development of future magnetocaloric devices. ; This work was in part financed by the RES4Build project, which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No.814865 and the ENOVHEAT project which was funded by the Innovation Fund Denmark (contract no 12-132673). We wish to thank Mike Wichmann and Jørgen Geyti for their technical assistance in the construction of the MagQueen device. The authors also acknowledge Jens F. S. Borchsenius for electronic expertise. Tian Lei is acknowledged for his modeling work. Furthermore, the authors ...