磁制冷及磁制冷材料的研究进展

一、磁制冷简介 传统压缩制冷技术广泛应用于各行各业,形成了庞大的产业,但它存在两个明显的缺陷：制冷效率低且氟利昂工质的泄漏会破坏大气臭氧层。自2000年起蒙特利尔协议生效,污染大气环境及破坏大气臭氧层的氟里昂制冷剂将逐渐被禁用,新的气体制冷剂{如HFC-134a）相继问世并已进入商品化生产。磁制冷作为一项高新绿色制冷技术,与传统压缩制冷相比具有如下竞争优势：1．无环境污染：2高效节能;3．易于小型化：4稳定可靠：     

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。     

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.     

磁制冷技术的应用与研究前景

磁制冷技术是一种极具发展潜力的制冷技术,其具有节能、环保的特点.介绍了磁制冷的工作原理、磁性材料的选择与研究进展情况,磁制冷循环及磁制冷机的研究进展,并指出磁制冷技术发展需要解决的问题.     

磁制冷材料中一级磁相变的研究进展

磁制冷技术作为21世纪的新一代制冷技术已经受到了关注。因此近年来具有一级磁相变的磁制冷材料成为全球学术界的一个研究热点,并越来越受到工业界的重视。主要介绍了磁制冷材料中的一级磁相变特点,综述了具有一级磁相变的磁制冷材料的研究进展和应用现状。最后展望了具有一级磁相变的磁制冷材料的发展趋势。     

磁制冷技术最新研究进展

磁制冷技术作为一种环保高效的新型制冷技术,受到了越来越多人的关注。与传统的气体压缩式制冷相比,磁制冷具有非常大的竞争力。随着材料科学和制冷循环理论等的不断发展,磁制冷技术必然有着广阔的发展前景。阐述了磁制冷技术的工作原理和典型磁制冷循环的研究进展情况,重点介绍了磁性材料以及活性蓄冷器的最新研究现状。     

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.     

室温磁制冷研究新动态及应用

室温磁制冷是磁制冷技术发展的必然趋势.本文介绍了近10年室温磁制冷研究的最新动态,分析了磁制冷循环理论研究的结果,详细说明了室温磁制冷材料和样机的新近成果,并对室温磁制冷的商业化应用前景进行了展望.     

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。     

Configuration and performance analysis of magnetic refrigerators

The commercialization of magnetic refrigerators depends upon the ability to meet performance targets while having acceptable equipment costs. This paper links device design parameters and performance of magnetic refrigerators to the cost of cooling delivered. A device configuration parameter, D, is defined that links the field volume to the volume of magnetocaloric material. Combined with the magnet performance parameter, efficiency, and specific exergetic cooling, the cost structure of a magnetic refrigerator is determined. Some magnetic refrigerators reported in the literature are classified using their configuration parameters, and are then compared in terms of demonstrated performance using results available in the literature. The required improvement in performance is calculated such that the cost of a magnetic refrigerator would be equivalent to a conventional compressor-based device. Finally, some of the reasons for different performance are discussed with a focus on opportunities for improvements.     

Design of a new magnetic refrigeration field source running with rotating bar-shaped magnets

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) is a prime candidate for the next generation of cooling systems. The essential components of magnetic refrigeration are the magnetic field generator and the magnetocaloric material. Although, several permanent magnet systems (magnetic field sources) for MR have been developed, recent development in magnetic refrigeration technology has encouraged researchers all over the world to think about new and original systems. This paper aims to describe a new and original magnetic refrigeration system based on a simple principle of magnetism called the Halbach effect. The proposed system is running with rotating bar-shaped magnets. This structure provides the desired varying magnetic field to the magnetocaloric material. Several configurations for the proposed systems have been investigated and presented in this paper. The design and modeling have been accomplished by using the finite elements method.     

A test stand to study the possibility of using magnetocaloric materials for refrigerators

A laboratory test stand for magnetocaloric effect investigations has been developed. The test stand is compact and easily reconfigurable. Gadolinium in the form of particles is used as a refrigerant. The material is magnetized/demagnetized due to the reciprocating motion of a magnetic bed. A Halbach array of permanent magnets is employed as a magnetic field source. It generates a magnetic field of about 1 T. In order to decrease the distance along which the magnetic bed has to move, a magnetic shield was used which limits the range of external magnetic field influence. The effectiveness of the shielding and the decrease in magnetic field intensity were shown in the form of magnetic field distribution maps. The paper presents first experimental results which are measured as the temperature difference between the two outermost reservoirs. The achieved results are promising – the temperature span between the heat exchangers amounts to about 2 °C.     

磁流体的制备及应用

磁流体是具有广阔应用前景的功能液体。本文阐述了磁流体的主要制备方法,讨论了表征其性能的主要参数,着重介绍了磁流体在工程领域、生物医药、物质分选以及环境治理等方面的应用,展望了今后磁流体的研究与发展方向。     

磁制冷循环分析

磁制冷循环是磁制冷技术中的重要环节,为磁制冷机的高效运行提供了理论基础.本文结合磁制冷循环的理论研究,详细介绍了磁制冷基本循环和活性蓄冷器(Active Magnetic Regenerator,AMR)循环,重点分析了影响循环的不可逆因素,并对磁制冷循环的发展进行了展望.     

磁性复合纳米材料研究进展

磁性复合纳米材料由于其强大的功能性已成为现在材料研究的热点。本文从其制备、修饰、应用进行了详细介绍,并针对目前该领域中存在的问题,提出了一些解决方法。     

Current status of SMES in Korea

The first superconducting magnetic energy storage (SMES) in Korea was fabricated in 1987. During 15 years after this, several SMES projects were carried out and many improvements were made. Presently, two main SMES projects are undergoing in Korea. One is low T_c SMES commercialization project and the other is HTS SMES design project. This paper describes a brief history of SMES development and the two main undergoing SMES projects in Korea.     

Development of the tandem reciprocating magnetic regenerative refrigerator and numerical simulation for the dead volume effect

In this paper, the development of the tandem reciprocating room-temperature active magnetic regenerative refrigerator and the numerical simulation for the effect of the dead volume are presented. The dead volume effect is analyzed by establishing a one-dimensional time-dependent model for the active magnetic regenerator (AMR). The cooling power at the mass flow rate of 5 g s⁻¹ water and a temperature span of 20 K is reduced from 4 W to 2 W when the length of the dead volume (D_DV = 12 mm) is increased from 15 mm to 30 mm. The numerical results indicate that the minimization of dead volume facilitates the improvement of the AMR performance. In particular, the components and the parameters of AMR system are demonstrated. The printed circuit heat exchangers (PCHEs) are employed as the warm end heat exchangers in order to minimize the dead volume of the system. The experimental apparatus includes two active magnetic regenerators containing 186 g of Gd spheres. The maximum no-load temperature span of 26.8 K and a maximum cooling power of 33 W at a zero temperature span were obtained with the frequency of 0.5 Hz under the maximum field of 1.4 T.     

A new semi-analytical method analyzing the magnetic field in unbalanced magnetron sputtering system

A new method, semi-analytical method (SAM), is first applied to calculate and analyze the magnetic filed in unbalanced magnetron sputtering system, and introduced in detail. An analytic solution of the scalar magnetic potential in the system can be acquired by the SAM. Its unknown number is much less than that in the numerical method. The analytic series expression of magnetic flux density can be easily obtained directly by differentiating the scalar magnetic potential function, and it can also easily ensure the precision of solving the magnetic flux density. The comparison of results between the values measured by experiment and the values calculated by the SAM has shown correctness and effectiveness of this method. The SAM cannot only accurately describe the distribution of magnetic flux density and optimize magnetic field in unbalanced magnetron sputtering system, but also be conveniently used for the simulation about plasma distribution and thin film growth.     

Estimation on Magnetic Refrigeration Material （Gd1-xREx）5Si4 （RE=Dy, Ho）

A systematic (Gd1-xREx)5Si4 (RE=Dy, Ho) alloys are investigated to estimate their magnetocaloric effect.The Curie points of (Gd1-xREx)Si4 alloys can tunable from 266 K to 336 K when RE=Dy, Ho; x=0～0.35 and 0～0.15, respectively, and decrease nearly linearly with increasing x. These alloys keep orthorhombic structures Ge5Sm4 and exhibit second order transition when they experience in a change magnetic field at about Curie when magnetic field changes 0～2 T. The adiabatic temperatures changes (△Tad) of these alloys at Curie points are larger than 1 K in a field change 0～1.4 T, the curve of △Tad is wide as that of Gd. The relative cooling power is about 0.8～0.9 J/cm3 when field changes 0～2 T, 55% of that of Gd. Comparing with Gd5(Si1-xGex)4, these alloys do not contain expensive element Ge, so that their cost are lower than the former. Because they could work at temperature region 260～340 K due to their Curie points can be tuned, which is an advantage comparing with Gd, these alloys are potential magnetic refrigerants working in a magnetic refrigerator with a low magnetic field at room temperatures.