Solid state magnetic refrigerator

Highlights: ► One proposes a magnetic refrigerator not requiring the use of fluids. ► Materials whose thermal conductivities depend on an applied magnetic field are used. ► Numerical simulations show that the coefficient of performance attained reaches 1.5. ► The device can be triggered from cooler to heat source by varying the frequency. - Abstract: The viability and operation of a fully solid state magnetic refrigeration system with envisaged applications on chip, sensor and device cooling is here tested using numerical simulations. The proposed system relies on the combined use of materials displaying the magnetocaloric effect and of materials whose thermal conductivities are controlled by an external magnetic field. This allows the switching of the heat flow direction in sync with the temperature variation of the magnetocaloric material, removing the necessity to use fluids which has for long hindered the implementation of magnetic refrigeration. We have found the optimum operating conditions of the proposed refrigerator, for which a cooling power density of ∼2.75 W cm−2 was obtained for an operating temperature of ∼296 K, using Gadolinium as the magnetocaloric material and an applied magnetic field of 1 T. The coefficient of performance (COP) achieved by this refrigerator was found to be COP ∼1.5, making it a viable alternative to thermoelectric refrigeration.