INITIAL RESULTS OF A TEST-BED MAGNETIC REFRIGERATION MACHINE WITH PRACTICAL RUNNING CONDITIONS

摘要

For a direct characterization of magnetocaloric materials, the measurements are generally made in adiabatic conditions. In such conditions, the initial temperature of the material is stabilized and then the magnetic field is changed from 0 T to a given finite value. However, in the majority of magnetic refrigeration systems, magnetocaloric materials are magnetized and demagnetized in non adiabatic conditions. Furthermore, almost nobody pays attention to the measurement of △T in actual conditions encountered in magnetic systems. At present a test-bed modelled and designed in cooperation with Cooltech Applications, to characterize magnetocaloric materials in practical conditions, was realized in the Institute of the Thermal Sciences and Engineering (IGT, Yverdon-les-Bains, Switzerland). This system allows the measurement of temperature differences and forces acting on magnetocaloric materials as a function of temperature and frequency, during magnetization-demagnetisation cycles, with a magnetic source having an induction field of about 2 Tesla. In this article initial results of forces and temperature differences obtained with some magnetocaloric materials are reported.