New concept for magnetocaloric heat pumps based on thermal diodes and latent heat transfer.

Abstract

Since the beginning of the last decade, several dozens of magnetocaloric heat pump systems have been built by different groups. Basically all of these systems are based on the Active Magnetic Regenerator (AMR) concept, where a heat transfer fluid is actively pumped through a bed of magnetocaloric material in order to transfer thermal energy to hot and cold side heat exchangers. Hereby several powerful systems were built, generating large temperature spans of more than 50 K while others provided large cooling capacities of several kW. However, up to now no system has been built which provides large temperature span and cooling capacity while having a coefficient-of-performance (COP) better than standard compressor-based cooling systems [1]. In this work a new concept and first experimental data of a magnetocaloric heat pump will be presented. In this concept, the heat transfer is realized by the combination of magnetocaloric material with thermal diodes which are based on latent heat transfer. Similar to thermosyphons, thermal energy is efficiently transported by condensation and evaporation processes leading to heat transfer rates which are several orders of magnitude larger than in conventional systems. At the same time, no additional pumps are required for transporting the heat exchange fluids, enabling systems which large temperature spans and competitive COPs.