Polymer-bonded La(Fe, Mn, Si)13Hx heat exchangers with optimized magnetocaloric properties

Three main issues need to be solved before the magnetic refrigerators will turn from prototypes to the mass production: (1) the price of the magnetic system, made from permanent magnets and providing the magnetic field change of 1-2 T, needs to be significantly reduced; (2) the switching of heat exchange fluids should be drastically accelerated and the hydraulic valves should be able to commutate the hot and cold circuits at frequencies of 20-50 Hz; (3) The time of heat transfer from the magnetocaloric material to the liquid should be reduced down to 50-20 ms and on this time scale the heat exchange should be 80-90 % of the theoretical efficiency. This last issue requires: magnetocaloric materials with outstanding MCE, excellent mechanical integrity and high thermal conductivity shaped into a porous structure with fine straight channels. This work aims to fulfill these requirements.