A COMPARISON BETWEEN FIRST AND SECOND ORDER PHASE MAGNETIC TRANSITION MATERIALS FOR AN AMR REFRIGERATOR AT ROOM TEMPERATURE

The main objective of this paper is to investigate the effect of the different magnetic materials on the refrigeration capacity and on the efficiency of the AMR cycle, since that different materials for magnetic refrigeration applications at room temperature have been tested. To this hope, a practical 2D model for predicting the refrigeration capacity and the efficiency of an AMR cycle in the room temperature range has been developed. The core of a magnetic refrigerator system is the Active Magnetic Regenerator (AMR). It is a special kind of thermal regenerator, made of magnetic material which works both as a refrigerating medium and such as a heat regenerating medium. The performance of an AMR system strongly depends on the magnetocaloric effect (MCE) of the magnetic material used to build the regenerator. At the Curie temperature a magnetic material exhibits its maximum MCE. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). Different magnetic materials have been considered as refrigerant: pure gadolinium, second order phase magnetic transition Pr0.45Sr0.35 MnO3 and first order phase magnetic transition alloys Gd5(SixGe1-x)4,LaFe11.384,Mn0.356Si1.26H1.52,LaFe11.05Co0.94Si1.10 and MnFeP0.45As0.55.