磁制冷发展现状及趋势：Ⅱ磁制冷技术

简要介绍了磁制冷实现的原理,概括了磁制冷与气体压缩制冷的差异,比较了4种磁制冷循环的优缺点及适用场合,重点评述了室温温区磁制冷样机的研究进展,分析了磁制冷的关键技术,最后给出了磁制冷的潜在市场并展望了发展趋势。     

磁布雷顿制冷循环

讨论并介绍了磁布雷顿制冷循环,指出磁布雷顿制冷循环具有某些独特优点,因而也是磁制冷新技术发展中不可忽视的一种重要循环方式。     

一种极具发展潜力的制冷技术--磁制冷

介绍了一种历史悠久但又极具发展潜力的制冷方式-磁制冷技术.从磁制冷的基本原理-磁热效应(MCE)出发,分别从熵和热力学的角度分析了MCE,给出了MCE的表征参数及常用测试方法,列举了常见的磁制冷循环及几种典型的磁制冷机,总结了磁制冷技术的研究历史,并对其进行了展望.     

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.     

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。     

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.     

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.     

磁致冷材料的发展与研究概况

介绍自１９１８年～１９９０年磁致冷材料及制冷技术的发展、应用与研究概况。国外磁致冷研究，在低温段已逐渐成熟并在某些领域得到了应用；在室温段也取得了重要进展，这对发展无氟污染的磁冰箱具有重要意义。在磁致冷材料的研究中，稀土元素发挥了极重要的作用。     

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。     

Design and performance of a room-temperature hybrid magnetic refrigerator combined with Stirling gas refrigeration effect

The experimental prototype described in this work is a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling gas regenerative refrigeration effect. In this prototype, gadolinium sheets are packed in the regenerator matrix for both Stirling and active magnetic regenerative refrigeration. Experimental tests were carried out to measure the cooling performance of this hybrid prototype. The influence of the phase angle on the cooling performance was investigated, and a reasonable phase angle of 90° was determined to obtain optimal cooling performance. By combining the two refrigeration effects, a minimum cooling temperature without heat load of 3.5 °C was reached, which is lower than that of 6.5 °C for the pure Stirling refrigeration effect without the magnetic cooling effect. The results of this study show that the cooling performance is improved by 24% for the hybrid effects compared with that exploiting only the Stirling gas refrigeration effect.     

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.     

The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)

The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum temperature span and the maximum cooling capacity of 20-40% for both parallel plate and packed bed regenerators. The maximum cooling capacity is shown to depend very weakly on the ramp rate of the magnetic field. Reducing the temporal width of the high field portion of the magnetic field profile by 10% leads to a drop in maximum temperature span and maximum cooling capacity of 5-20%. An increase of the magnetic field from 1 T to 1.5 T increases the maximum cooling capacity by 30-50% but the maximum temperature span by only 20-30%. Finally, it was seen that the influence of changing the magnetic field was more or less the same for the different regenerator geometries and operating parameters studied here. This means that the design of the magnet can be done independently of the regenerator geometry.     

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.     

A single-stage pulse tube cooler reached 12.6 K

A single-stage G-M type pulse tube cooler (PTC) was designed and tested to explore the lowest attainable refrigeration temperature and to further improve the cooling performance in the temperature range of 15-40 K. The magnetic material Er₃Ni was used as part of the regenerative material besides the phosphor-bronze and the lead so as to improve the efficiency of the regenerator. With an input power of 6 kW, a lowest no-load refrigeration temperature of 12.6 K was obtained, which is a new record for the single-stage PTC. The cooling capacity at 15-40 K was also significantly improved, which may extend the application of the single-stage PTC for the cooling of superconductors and cryopumps.     

Magnetic refrigerator for hydrogen liquefaction

This paper reviews the status of magnetic refrigeration system for hydrogen liquefaction. There is no doubt that hydrogen is one of most important energy sources in the near future. In particular, liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. When we compare the consuming energy of hydrogen liquefaction with high pressurized hydrogen gas, FOM must be larger than 0.57 for hydrogen liquefaction. Thus, we need to develop a highly efficient liquefaction method. Magnetic refrigeration using the magneto-caloric effect has potential to realize not only the higher liquefaction efficiency >50%, but also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and AMR (active magnetic regenerator) cycle for precooling stages. For the Carnot cycle, we develop the high efficient system with >80% liquefaction efficiency by using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems, which transferred the working fluid. We confirmed the AMR effect with the cooling temperature span of 12 K for 1.8 T of the magnetic field and 6 s of the cycle. By using the simulation, we estimate the efficiency of the hydrogen liquefaction plant for 10 kg/day. A FOM of 0.47 is obtained for operation temperature between 20 K and 77 K including LN₂ work input.     

Numerical investigations on internal temperature distribution and refrigeration performance of reciprocating active magnetic regenerator of room temperature magnetic refrigeration

A two-dimension porous medium model for a reciprocating active magnetic regenerator (AMR) of room temperature magnetic refrigeration has been developed. The thermal diffusion effect, heat flux boundary effect and variable fluid physical properties are considered in the model. In the paper, we compare the numerical results of the porous medium model with the experimental data and the calculation results of one-dimension Schumann model to validate our model. Our model can simulate the operation of the reciprocating AMR effectively. With the present model, the internal heat exchange between the two phases is numerically investigated. The two dimensional temperature distributions of the magnetic refrigerant and the refrigeration performance of AMR are obtained, and the influence of the heat flux boundary effect and the variable fluid properties on them is discussed. AMR can achieve a maximum refrigeration capacity of 293.7 W with a corresponding coefficient of performance (COP) of 5.4.     

Review on research of room temperature magnetic refrigeration

Room temperature magnetic refrigeration is a new highly efficient and environmentally protective technology. Although it has not been maturely developed, it shows great applicable prosperity and seems to be a substitute for the traditional vapor compression technology. In this paper, the concept of magnetocaloric effect is explained. The development of the magnetic material, magnetic refrigeration cycles, magnetic field and the regenerator of room temperature magnetic refrigeration is introduced. Finally some typical room temperature magnetic refrigeration prototypes are reviewed.     

Experimental results for a magnetic refrigerator using three different types of magnetocaloric material regenerators

Magnetic refrigeration is a potentially environmentally-friendly alternative to vapor compression technology because it has a potentially higher coefficient of performance and does not use a gaseous refrigerant. The active magnetic regenerator refrigerator is currently the most common magnetic refrigeration device for near room temperature applications, and it is driven by the magnetocaloric effect in the regenerator material. Several magnetocaloric materials with potential magnetic refrigeration applications have recently been developed and characterized; however, few of them have been tested in an experimental device. This paper compares the performance of three magnetocaloric material candidates for AMRs, La(Fe,Co,Si)₁₃, (La,Ca,Sr)MnO₃ and Gd, in an experimental active magnetic regenerator with a parallel plate geometry. The performance of single-material regenerators of each magnetocaloric material family were compared. In an attempt to improve system performance, graded two-material regenerators were made from two different combinations of La(Fe,Co,Si)₁₃ compounds having different magnetic transition temperatures. One combination of the La(Fe,Co,Si)₁₃ materials yielded a higher performance, while the performance of the other combination was lower than the single-material regenerator. The highest no-load temperature span was achieved by the Gd regenerator.     

磁致冷材料的发展及研究现状

磁致冷作为一种新的制冷方式而受到的重视。评述了低温区和高温区的磁致冷工质材料的研究过程及现状,并指出多种成分的复合工质可实现宽温区磁致冷,稀土合金及具有巨磁阻效应的钙钛矿陶 材料可能是研究可实际应用的室温区磁致冷材料的新方向。