室温磁制冷工质材料的研究进展

磁制冷技术是一种高效、环保的新型制冷技术,应用前景非常广阔.室温磁制冷工质是室温磁制冷技术发展的关键因素之一.介绍了磁制冷工质用于制冷技术的原理、室温磁制冷工质的选择依据及发展现状,并对室温磁制冷工质技术的发展进行了展望.     

室温磁制冷工质研究进展

室温磁制冷工质的研发是决定室温磁制冷技术发展的关键因素之一,后者是一种高效、环保的新型制冷技术,应用前景非常广泛.本文介绍了磁性工质用于制冷技术的原理、磁性工质的选择依据、室温磁制冷工质的发展现状及活性蓄冷器的相关技术,并对室温磁制冷工质技术的发展进行了展望.     

近室温磁制冷合金材料的研究进展及发展前景

磁制冷技术是一种高效节能、绿色环保、可靠性强的先进制冷技术,其核心原理是磁性材料的磁热效应,即磁制冷工质等温磁化时向外界放出热量,绝热退磁时从外界吸收热量.理论上所有的磁性材料都具有磁热效应,但只有极少数具有显著磁热效应的磁性材料可用于磁制冷.因此,研发具有较大磁热效应的磁制冷工质是决定磁致冷技术能否得到应用和推广的关键因素.经过几十年的发展,人们陆续发现了许多性能优异的磁制冷材料,推动和促进了磁制冷技术的发展.目前,磁制冷技术在20 K以下的低温区已经得到了较为广泛的应用,如液氦的制备、低温物理研究以及航空航天等领域都采用了磁制冷技术.低温区的磁制冷材料通常为顺磁状态,其构型熵可以忽略不计,但随着温度的升高,用于低温区磁制冷的顺磁材料的晶格振动变大,构型熵对磁制冷系统的影响不可忽略,即传统的顺磁态磁制冷工质在近室温区已不再适用,因此研发近室温区的磁制冷材料具有重要意义.近20年间,国内外研究者对近室温区磁制冷材料进行了大量研究并取得了许多重要成果,如以Gd(SiGe)4、La(FeSi)13、MnAs合金和NiMn基Heusler合金等为代表的具有优异磁热效应的一级相变磁制冷材料,这些合金的磁热效应通常是由结构相变与磁相变的叠加引起的,但常常伴有较大的热滞与磁滞损耗,进而会大幅度降低磁制冷的效率.除了一级相变磁制冷材料外,还有稀土Gd及其化合物、Gd基非晶态合金等具有二级磁相变的近室温磁制冷材料.其中,Gd基非晶态合金具有制冷温区宽、涡流损耗低、磁滞低、成分范围宽、耐腐蚀和易于加工等优点,其较宽的制冷温区特别适合室温埃里克森磁制冷循环,具有广阔的应用前景.本文简要介绍了磁热效应的原理以及磁制冷技术的发展,重点介绍了近室温磁制冷材料的磁热性能和最新研究进展,包括Gd(SiGe)4、La(FeSi)13、MnAs合金、NiMn基Heusler合金等一级相变磁制冷材料和具有二级磁相变的Gd基非晶态合金,并分析了它们作为磁制冷材料的优点和存在不足,讨论了各系材料未来的发展方向和趋势.     

室温磁制冷工质研究现状

室温磁制冷技术是环保、高效的新型制冷技术,它在家电、工业、军事领域都有广阔的应用前景。其中磁工质是室温磁制冷技术的关键。概述了磁制冷的原理,详细介绍了GdM、La(Fe,Si)13、MnFe(PxAs1-x)、Mn3XC(N)、Heusler合金磁工质现阶段的发展状况及存在的不足,并展望了磁制冷材料的发展前景。     

室温磁制冷研究进展

室温磁制冷技术是一项新的制冷技术,具有高效环保的特点,应用前景十分广阔,有望取代传统的蒸气压缩式制冷方法。阐述了磁热效应的原理,系统介绍了室温磁制冷中磁性材料、磁制冷循环、蓄冷器以及典型制冷机的发展情况,并对室温磁制冷的发展进行了展望。     

磁热效应和室温稀土磁制冷材料研究现状

室温磁制冷技术具有环保、可靠性好、效率高等优点.被认为是一种很有前景的新型制冷技术.概述了磁性材料的磁热效应概念以及磁热效应大小的表征方法,详细介绍了目前Gd5Si2Ge2、La(Fesi)13、RECo2及RE2Fe17等系列化合物稀土磁制冷材料的研究现状,并简要对比和评价了不同材料的相关性能,展望了室温稀土磁制冷材料的发展前景.     

室温磁工质与磁制冷机的研究和开发

室温磁制冷作为一种高能效、环境友好和运行可靠的制冷技术,具有广阔的应用前景。室温磁制冷技术利用磁工质的磁热效应以及AMR循环实现制冷。在过去数十年的探索中,室温磁制冷的研究主要集中于磁工质的研发和磁制冷机的设计。本文综述了目前已开发的几种典型的室温磁工质以及研制的磁制冷样机。目前研究较丰富的室温磁工质主要包括稀土金属Gd及其合金、NaZn₁₃型La(Fe, Si)₁₃系合金以及Fe₂P型MnFePAs系合金,本文对它们的磁热性能进行对比并分析存在的实际应用问题。基于运行方式的不同,目前研制的磁制冷样机主要分为往复式和旋转式,介绍了不同研究机构研发的磁制冷样机的实验参数与制冷性能。回顾了室温磁制冷技术在不同领域已取得的实际应用,并对该技术未来的发展趋势进行展望。     

使用永磁体的室温磁制冷样机研究

介绍了使用1．7T永磁体制作室温磁制冷样机实验机的情况。在使用主动式磁蓄冷器(AMR)的循环方式下，达到了8K的温差，说明了进一步制作较大而且更为实用的永磁体室温磁制冷样机的可行性。     

Design of a permanent magnetic circuit with air gap in a magnetic refrigerator

We calculate the magnetic field distribution of a permanent magnetic circuit with an air gap in a magnetic refrigerator by a finite-element method, and compare the field strengths of different structural parameters of the magnetic circuit. We show how the structure of the magnetic circuit can be optimized and present some approaches to improve the structure for a specific magnetic circuit. The main purpose is to provide basic parameters for the design of a practical magnetic refrigerator.     

Performance of a room-temperature rotary magnetic refrigerator

We have designed and operated a rotating-magnet type AMR (active magnetic regeneration) refrigerator that uses water as a heat transfer fluid. Four kinds of gadolinium-based alloy are used as magnetic materials. A magnetic field of 0.77 T is applied by neodymium permanent magnets. The refrigerator produces a maximum cooling power of 60 W around 10 °C. An optimal time for one cycle exists, and it depends on the water flow rate and the frequency of magnetization and demagnetization. Enhancement of the water flow rate and the frequency is known to be essential for increasing the cooling power of this refrigerator.     

Room-temperature magnetic refrigerator using permanent magnets

A magnetic refrigerator device based on adiabatic magnetic refrigeration is described. The magnetic material is cyclically magnetized and demagnetized by permanent magnets in an adiabatic process. A temperature difference of 1.6 K between the hot and cold regions was obtained under a low magnetic field (0.3 T). Gadolinium was the magnetic material used in experiments at room temperature. The range of working temperatures is between 70 and 300 K for a variety of active magnetic materials. The optimized experimental setup increased the device efficiency by achieving a temperature difference between hot and cold sources up to 5 K     

小型室温磁制冷系统的研制

设计并搭建了一台小型室温磁制冷系统,进行了初步性能实验研究。系统采用双层同轴Halbach永磁组,磁体旋转后可在中心处获得最大1.3 T磁场;在主动磁回热器两端设计了双通道流路,可有效避免系统流体死体积;驱动控制系统利用多轴伺服驱动器对磁体和水力活塞运动进行控制。样机采用了直径0.55—0.80 mm钆球作为制冷工质、p H值为11的氢氧化钠溶液为换热流体,进行了初步实验研究,考察了利用系数对制冷温跨的影响等。在高低温端绝热与运行频率0.60 Hz的情况下,实验获得13.3 K的最大无负荷制冷温跨;在运行频率为0.4 Hz时最佳利用系数为0.35,此时无负荷制冷温跨为12.1 K。     

Design and performance study of the active magnetic refrigerator for room-temperature application

A room-temperature magnetic refrigerator, consisting of permanent magnet, active magnetic refrigeration (AMR) cycle bed, pumps, hydraulic circuit, active magnetic double regenerator cycle (AM2RC) and control subsystems, has been designed. The magnetic field is supplied by NdFeB permanent magnets. The AMR bed made by stainless steel 304 encloses gadolinium particles as the magnetic working substance. Each part of the refrigerator is controlled by the programmable controller. The different standard heat exchangers are employed to expel heat. The cycle performance of this self-designed facility is analyzed using Langevin theory. The results provide useful data for future design and development of room-temperature magnetic refrigeration.     

Improvements of a room-temperature magnetic refrigerator combined with Stirling cycle refrigeration effect

A high pressure hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect at room temperature is studied here. In the apparatus, a helium-gas-filled alfa-type Stirling refrigerator uses Gd sheets as the regenerator and the regenerator is put in a magnetic field varying from 0 to 1.4 T, which is provided by a Halbach-type rotary permanent magnet assembly. With an operating pressure of 5.5 MPa and a frequency of 2.5 Hz, a no-load temperature of 273.8 K was reached in 9 minutes, which is lower than that of 277.6 K for pure Stirling cycle. For the hybrid operation, cooling powers of 40.3 W and 56.4 W were achieved over temperature spans of 15 K and 12 K, respectively. For the latter case, the cooling power improves by 28.5% if compared with that exploiting only the Stirling cycle refrigeration effect.     

The energy performances of a rotary permanent magnet magnetic refrigerator

The interest of the scientific community regarding magnetic refrigeration at room temperature is constantly growing. In recent years, there has been an increase in the experimental work relating to both new prototypes and new magnetocaloric materials. The magnetic refrigerators built to date still have some limitations that make them uncompetitive when compared with conventional vapour compression systems. However, among the different configurations realized, one can recognize that rotary devices, having rotating magnets and static regenerators, are of particular interest because of their good energy performances. In this paper, we report an experimental investigation on the identification of the energy performances of a Rotary Permanent Magnet Magnetic Refrigerator. Employing 1.20 kg of gadolinium and operating at a temperature of heat rejection equal to 296 K, the system was subjected to different operating conditions obtained by varying the thermal load, volumetric flow rate of the regenerating fluid and cycle frequency.     

无接触传动永磁齿轮磁场的数值模拟

永磁齿轮作为一种新型的磁力传动机构,主动轮与从动轮之间没有直接表面接触,是通过磁场相互耦合产生的磁力来实现力矩和功率的传递.为了对永磁齿轮的传动特性进行研究,对永磁齿轮的磁场进行分析计算,利用ANSYS有限元软件模拟永磁齿轮磁场在不同矩角时的磁感应线、磁感应强度的分布,得出永磁齿轮的矩角特性曲线.通过实验验证了永磁齿轮的矩角特性和低速时的啮合比.     

Theory of an anisotropic thermoelectric refrigerator in a magnetic field

It is shown that the difference between the specific thermal conductivity coefficients in the absence of an electric current and field has a substantial effect on the maximum temperature drop.Chernovitsy State University, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 6, pp. 729–732, June, 1994.