عنوان مقاله [English]
Nowadays, the energy crisis has become a real problem, so, peoples are looking for higher efficiency, and purer devices and systems to recover energy. The magnetic refrigeration system is a new technology; It based on the change of entropy invoked by the application of an external magnetic field on a paramagnetic or magnetic material. The recent achievements regarding magnetic refrigeration, especially near room temperature regions, largely rest upon the active magnetic regenerator (AMR) concept. The AMR cycle comprises four processes. During magnetization, the magnetic field is applied to the ferromagnetic refrigerant, resulting in an increase of its initial temperature due to the MCE. Maintaining the field, fluid flow regenerates the solid and rejects the MCE heat towards a warm sink. Next, the field is deactivated, resulting in a temperature drop of the solid refrigerant induced by the MCE. Because of the preceding regeneration process, the solid temperature is now lower than at the start of the cycle. Finally, fluid flows in the opposite direction regenerating the solid and allowing heat addition from a cold source. In this paper, a practical model for predicting the performance and efficiency of a bed of active magnetic regenerative refrigerators has been presented. The heat transfer fluid, driven by a pump, flows through the regenerator, which is a porous or multi tube magnetic media. For simplification, solid and fluid parts of the bed have been assumed to be two adjacent separated layers. Consequently, one dimensional relations consisting of two coupled energy equations are derived. Discretized equations have been solved by iteration. Ultimately, temperature distributions over each media and for different moments of the cycle time are obtained. By this model, other refrigeration system parameters, such as coefficients of performance and cooling capacity, have been predicted. The numerical results have been compared with preexistent limited experimental and other theoretical reports. Also, an investigation into the performance of a porous bed and a multi tube bed structure has been done and the results have been presented.