磁制冷循环与磁工质的选择原则

磁循环和磁工质的选择对于磁制冷的成败与否是至关重要的。本文的主要目的是讨论磁工质所必要的磁学和热学特性以及探讨适合于不同温区的磁循环。文章首先给出了铁磁或顺磁材料的随温度和外场而变化的磁熵的计算结果,以及此类材料的晶格熵随德拜温度而变化的关系。在熵分析的基础上,就可得出磁工质和磁循环的遣择原则。本文还讨论了分别适用于低于20K,20～77 K,近300K三温区的磁工质的选用。最后,文章指出,高效制冷工质和蓄冷器是获得室温磁制冷的关键所在。

THE SELECTION PRINCIPLE OF CYCLE AND REFRIGERANT FOR MAGNETIC REFRIGERATION

The main purpose of this paper is to discuss the necessary magnetic & thermal properties of refrigerants and to investigate the magretic cycles suitable for different temperature range. Firstly, the paper shows the calculation results of the magnetic entropy of ferromagnetic and paramagnetic material which is a function of temperature and applied field; secondly, the lattice entropy changed with the Debye temperature is given also. On the basis of etropy analysis, the selection principle of cycle and refrigerant for magnetic refrigeration is provided. And then, the results of recent investigations on magnetic refrigerants are sumed up, these refrigerants can be divided into three groups, one for the Carnot type magnetic refrigerator below 20 K, one for the Ericsson type refrigeration between 77 to 20 K and another one for the refrigerator near room temperature, Finally, the paper points out that high efficient refrigerant and regenerator is the key to achieve the magnetic refrigeration near room temperature.