Towards high cycle frequencies for magnetocaloric cooling systems - a proof of principle

The cooling power of a magnetocaloric cooling system scales with the cycle frequency. Therefore, a high cycle frequency is mandatory for a cost-efficient system, since an equivalent pumping power can be achieved with less cost-intensive permanent magnet material. This is of great importance prospective large-scale market introduction of magnetocaloric systems. We present a novel approach of latent heat transfer in combination with thermal diodes in order to reach higher cycle frequencies compared to the state of the art. The cooling system consists of several vacuum segments containing the magnetocaloric material. The segments are linked via passive check valves. Heat transfer from one segment to the next segment is caused by condensation and evaporation of the working fluid. Thereby, the passive check valves operate as thermal diodes leading to a unidirectional heat flux from the cold- to the hot-side of the heat exchanger. A single segment cooling system consisting of one segment of magnetocaloric material, a fluid backflow, and two check valves has been designed and characterised in order to investigate the frequency limitations. The dependency between cooling power and generated temperature span has been evaluated for various frequencies. In order to increase the temperature span between hot- and cold-side of the heat exchanger a setup with multiple segments has been investigated.