Performance evaluation of an active magnetic regenerator for cooling applications - part I: Experimental analysis and thermodynamic performance

In this first part of a two-part paper, a new active magnetic regenerator (AMR) laboratory apparatus is presented and evaluated. The setup is composed of a nested Halbach cylinder magnetic circuit (maximum magnetic flux density of 1.69 T) assembled in phase with a double effect displacer that provides the cold and hot blows to the regenerator. A single packed-bed regenerator with 195.5 g of gadolinium spheres is used in a discontinuous (i.e., reciprocating) cycle. The system performance is evaluated in terms of characteristic curves (i.e., cooling capacity as a function of temperature span), coefficient of performance and second-law efficiency as a function of the utilization factor and operating frequency. Maximum values of COP have been identified for a given temperature span. The maximum values of second-law efficiency were obtained at system temperature spans between 15 and 20 K.