Composite Magnetic Refrigerants for an Ericsson Cycle: New Method of Selection Using a Numerical Approach

Abstract

The efficient operation of an Ericsson cycle requires the magnetic entropy change (AS) be constant as a function of temperature. To realize this condition using composite materials, a numerical method has been developed to determine the optimum proportions of the components. The Gd_xEr_1-x((x = 0.69, 0.90) alloys have been used to investigate the validity of the numerical method. The values of ∆S have been determined from experimental magnetization curves of these alloys, in the 0.1–9 T magnetic field and the 200–290 K range. The calculations have led to the mass ratio y = 0.56 for the composite (Gd_0.90Er_0.10)_y(Gd_0.69Er_0.31)_1-y. The ∆S of this composite is fairly constant in the 225–280 K range. To confirm this result, the magnetization curves of the composite material have been determined experimentally, and the corresponding ∆S was compared with the one predicted numerically. A good agreement was found proving the method’s ability to properly determine the required fractions of the refrigerant’s constituent materials.