Study On Heat Transfer Performance And Structure Of Active Magnetic Regenerator Of Room Temperature Magnetic Refrigeration

Magnetic refrigeration technology is a new kind of environment-friendly technology by magneto caloric effect, in which solid materials are used as working medium. But in recent years the development of magnetic refrigeration is subject to a block, of which the main factors include small magneto caloric effect, poor performance of the heat exchange and single structure. Based on the heat transfer characteristics of AMR, the heat transfer performance and structure of reciprocating magnetic refrigeration system are studied. The experiments were carried out under different conditions of velocities, delay time and environment, in which the temperature of ends of AMR was measured and magneto caloric effect of the system was analyzed to find the best conditions for improving the efficiency of refrigeration system. During the simulation study, the temperature, velocity, streamline and pressure distribution would be investigated with different inlet velocity of cylinder active magnetic regenerator. A new type of AMR was designed, of which the both sides were conical structure, making the heat transfer fluid flow smoothly and reducing the possibility of dead corner. In the active magnetic regenerator, flaky magnetic materials Gd was used and placed in parallel to each other. The simulation comparative results of two types of AMR were analyzed under the same condition. The main results showed that:1 According to the simulation, comparing the two types of AMR, the heat transfer rate of the flake was slightly less than that of the granular, but flowing property of the flake was superior to the granular, therefore, the design could be a reference in the comprehensive performance of AMR.2 In the experiment, by comparing the different velocities and different delay time, the condition of 160mm/s and 700 ms is best for the system and temperature fluctuations of AMR were very small and stable, which could provide refrigerating capacity for the cold end over a long time. The temperature difference between cold end and hot end of AMR could achieve the maximum of 16.8℃ and the largest magneto caloric effect was 3.6K, which is slightly lower than the theoretical maximum of 4.2 K.3 The environment condition had a great effect on lowest cold end temperature, the lowest temperature of cold end would decreased with the decreasing of environment temperature until stably, whose values were close to 2 ℃.