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Work is being done today to overcome the problems generated by conventional refrigeration (compression / expansion of a refrigerant) by following two parallel paths. In the first, we seek to maintain conventional technology and find new refrigerants less polluting. The second is to achieve a technological breakthrough and find new ways to achieve energy efficient systems while having a low environmental impact. This is the case of magnetic refrigeration which is the subject of this communication. Magnetic refrigeration is based on the magneto-caloric effect (MCE); an intrinsic property of certain magnetic materials that results in a change of their thermal state (hot/cold) during the variation of their magnetic state (magnetized/demagnetized) induced by an external magnetic field. The (MCE) decreases rapidly as the temperature of the material moves away from its transition temperature. To overcome this problem, it would be possible to use a combination of layers of different materials each having a transition temperature adapted to the local temperature, which would keep a sufficient EMC throughout the regenerator. But the question is how to stratify and place these materials along magnetic generator and what is the portion of each material in order to have better cold production. This present investigation serves to determine the best combination of two materials among six materials respectively having the Curie temperature (transition temperature) 270, 275, 280, 282, 285 and 290 [K °] and which are united on the common formula LaFe13 -xyCoxSiy. Our mathematical model is based on the laws of classical conservations, to take into account the porous structure of the generator (stacking of spheres) we use the model of (Darcy-Brikman-Forchheimer). To overcome the non-linearity of the mathematical model as well as the strong dependence between the dynamic field and the thermal field, the Simpler algorithm is used. At the end of this investigation we manage to draw the three essential points: 1-The material (layer) with the lower Curie temperature should be placed on the cold side of the refrigerating machine. 2-The combination (20%, 80%) is the most qualified to have the best cold-production. 3- The combination (80%, 20%) is the most disqualified and gives the lowest production. |
