The magnetic refrigeration is a new highly efficient and environmentally protective technology, which could be an actual solution for the typical problems of the vapour compression systems. 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 as a heat regenerating medium. The performance of an AMR system strongly depends on the magnetocaloric effect of the magnetic material used to build the regenerator. In the present paper, a model to simulate the thermal behaviour of an AMR has been introduced for predicting the performance of an AMR refrigerator system. Different magnetic materials have been considered as refrigerant: pure gadolinium, second order phase magnetic transition binary rare earth alloys (SOMT) and first order phase magnetic transition alloys (FOMT). The SOMT are GdxDy1!x and GdxTb1!x whereas the FOMT are Gd5(SixGe1!x)4 and MnAs1!xSbx. The magnetocaloric behaviour of gadolinium can be correctly predicted by the Weiss molecular field theory. This approach can be generalized for binary alloys with a second order phase transition. The behaviour of the MnAs1!xSbx alloys is described by means of a model based on the phenomenological approach of Bean Rodbell. Interpolation of empirical data is utilized for the evaluation of the magnetocaloric effect of Gd5(SixGe1!x)4 alloys. With this model, the refrigeration capacity, the power consumption and consequently the Coefficient of Performance of the cycle can be predicted. The results of the simulation clearly show that Gd5(SixGe1!x)4 is the best magnetic material with a COP that is always greater then that of a traditional vapour compression plant in the same operating conditions (from a minimum of +40% to a maximum of +62%).

The use of the first and of the second order phase magnetic transition alloys for an AMR refrigerator at room temperature: a numerical analysis of the energy performances

APREA, Ciro;MAIORINO, ANGELO
2013

Abstract

The magnetic refrigeration is a new highly efficient and environmentally protective technology, which could be an actual solution for the typical problems of the vapour compression systems. 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 as a heat regenerating medium. The performance of an AMR system strongly depends on the magnetocaloric effect of the magnetic material used to build the regenerator. In the present paper, a model to simulate the thermal behaviour of an AMR has been introduced for predicting the performance of an AMR refrigerator system. Different magnetic materials have been considered as refrigerant: pure gadolinium, second order phase magnetic transition binary rare earth alloys (SOMT) and first order phase magnetic transition alloys (FOMT). The SOMT are GdxDy1!x and GdxTb1!x whereas the FOMT are Gd5(SixGe1!x)4 and MnAs1!xSbx. The magnetocaloric behaviour of gadolinium can be correctly predicted by the Weiss molecular field theory. This approach can be generalized for binary alloys with a second order phase transition. The behaviour of the MnAs1!xSbx alloys is described by means of a model based on the phenomenological approach of Bean Rodbell. Interpolation of empirical data is utilized for the evaluation of the magnetocaloric effect of Gd5(SixGe1!x)4 alloys. With this model, the refrigeration capacity, the power consumption and consequently the Coefficient of Performance of the cycle can be predicted. The results of the simulation clearly show that Gd5(SixGe1!x)4 is the best magnetic material with a COP that is always greater then that of a traditional vapour compression plant in the same operating conditions (from a minimum of +40% to a maximum of +62%).
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/3912169
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