| Room temperature magnetic refrigeration is a new cooling method utilizing the magnetocaloric effect of magnetic material, which is environmentally friendly and more efficient and be promising to replace the vapor compression refrigeration. Now room temperature magnetic refrigeration attracts wide attention from all over the world. Facing to the problems of global warming and ozone hole, Gschneidner pointed out in his article’Thirty years of near room temperature magnetic cooling’ that the research work on magnetic refrigeration is meaningful and important to the world. From1976when Brown built room temperature magnetic refrigeration prototype, magnetic refrigeration developed fast. Many research groups have built their own magnetic refrigerators. Our lab has successively built reciprocating active magnetic regenerative (AMR) magnetic refrigerator, rotary AMR magnetic refrigerator and hybrid regenerative magnetic refrigerator which attract more attention. In1978, the concept of using an active magnetic regenerator (AMR) in the cooling device to facilitate heat transfer was introduced; in1983, AMR was further developed by Steyert and Barclay; in1990, Green built the first reciprocating magnetic refrigerator; in1997, the AMR built by the Ames Laboratory/Astronautics Corporation of America had excellent performance. University of Wisconsin firstly did some simulating calculations of magnetic refrigeration, after which our lab did some calculations of AMR and HR based on Fortran and had some meaningful results. We think the results can solve some problems on magnetic refrigeration. This text mainly focuses on some aspects of active regenerative magnetic refrigerator. It contains the following content:The first chapter introduces the development of magnetic refrigeration; an introduction to several typical materials, magnetic cooling cycles and the cycles fit for room temperature magnetic refrigeration. The last part of this chapter introduces the structure of AMR and mode of operation.The second chapter introduces a method of simulating calculation of the regenerative process of reciprocating active magnetic refrigerator based on matlab. This method is based on fundamental theory of heat transfer. Discretization of the governing equations, restoring the data after one cycle and importing the data of magnetocaloric effect of magnetic material are the foundation parts of the method. This chapter also introduces what is variable cycle operating mode of reciprocating active magnetic refrigerator and the difference between variable and fixed cycle operating mode. From the simulating calculation, we get some results concerning to the cycle time, extreme temperature span, cooling capacity and COP. We think these results can help us design and improve magnetic refrigerator.The third chapter focuses on permanent magnet of magnetic refrigerator and introduces a method of calculating magnetic field provided by permanent magnet based on theory of magnetic charge. We use this method to calculate the magnetic field provided by cuboid permanent magnet, permanent magnet used in hybrid regenerative refrigerator and rotary magnetic refrigerator. This calculation method contributes to design the system of magnet. A method of designing different system of magnet and a program about a new type permanent magnet, which is inexpensive and can provide almost the same magnetic field intensity as now, are also mentioned.The forth chapter introduces a method of measuring liquid thermal conductivity and the design of the device. The measurement is based on heat transfer theory and error function... |
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