共查询到19条相似文献,搜索用时 62 毫秒
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本文借助COMSOL多物理场耦合软件,构建了二维瞬态平板磁制冷微元模型和热电磁复合制冷微元模型,考察了热电臂厚度、电流、运行频率、外界对流换热系数对复合制冷性能的影响。模拟结果显示,在大多数工况下热电磁复合模型的比制冷功均大于磁制冷模型的比制冷功率;改变不同几何和运行参数对复合制冷性能有不同的影响。在研究工况范围内,改变热电臂厚度(0.05~0.5 mm)、电流(0.4~0.8 A)、运行频率(0.5~4 Hz)和对流换热系数(500~2000 W·m-2·K-1),热电磁复合制冷微元模型相比于平板磁制冷微元模型,制冷功率密度最大提高分别为2.05倍、2.12倍、2.68倍、1.87倍。本研究对后续开展热电磁复合制冷系统机理研究提供重要指导。 相似文献
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磁制冷材料的性能 ,可以用有效制冷容量RC来衡量 ,RC =ΔS× (T高 -T低) ,其中ΔS是可用磁熵度 ,T高 和T低 分别是制冷机的热端和冷端温度 .1997年 ,美国艾姆斯实验室的Gschneidner等报告了他们所发现的室温巨磁热效应材料Gd5Si2 Ge2 .不幸 ,后来的详细测试表明 ,该材料在磁制冷循环中会产生大的磁滞损失 ,从而使其应用价值受到影响 .在 5T的外场下 ,Gd5Si2 Ge2 的RC理想值是 30 5J/kg ,由于每循环的磁滞损失高达 6 5J/kg ,致使有效RC仅仅为 2 4 0J/kg .最近 ,来自美国国家标准技术研究院的ShallRD小组 ,发展了一种新的替代材料… 相似文献
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制冷就是使某一空间内物体的温度低于周围环境温度并能维持这个低温的过程。制冷及低温技术有着十分重要的应用,关系到国计民生的多个重要领域,如食品储藏、航空航天、医疗卫生、科学试验等。根据制冷产生的低温环境的不同,制冷技术大体分为三类,120K以上至环境温度以下为普通制冷,20-120K为深度制冷,OK以上至20K为低温和超低温制冷。早期制冷主要采用气体膨胀的方式来获取越来越低的低温,到1932年,荷兰人克西姆采用降低液氦压力的方法获得了0.7K的最低温度。这几乎达到了气体膨胀制冷的极限。 相似文献
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在室温磁制冷中铁磁体作为工作物质的可能性 总被引:2,自引:0,他引:2
在室温磁制冷中铁磁体是合适的工作物质.铁磁体内部存在的交换相互作用,使我们能够以较低的外场达到排出磁熵的目的.同时,铁磁体磁热过程本身的可逆性,使我们有可能用它构成高效的磁制冷机.本文从铁磁体磁热效应的基本实验事实出发,讨论磁制冷机工作物质选择的判据,强调真实磁化过程在制冷应用中的意义,利用分子场近似给出对材料选取有用的公式,通过对比指出,Fe基合金具有很好的应用前景. 相似文献
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介绍了一种斯特林回热式制冷效应和主动式磁制冷效应耦合的新型制冷循环。循环采用的回热填料钆既是磁制冷循环的磁热材料又是斯特林制冷的回热材料。通过斯特林回热式制冷循环和磁制冷效应的正面耦合叠加获得更优良的制冷效果。同时介绍了一种磁制冷回热器的数值计算模型,本模型是基于控制容积法计算的一维交变流动模型,并对常规回热器内填料能量控制方程进行了修正,考虑了磁性材料磁热效应的影响,添加内热源项。论文计算分析了系统相位角、压力和频率的变化对制冷性能的影响。文中给出的部分模拟结果对后续实验台的改造有一定的借鉴指导作用。 相似文献
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基于三种MnFe基磁热材料的热容及等温磁熵变随温度变化的实验数据,本文应用热力学理论设计一种新型MnFe基复合磁热材料,获得三种组分磁热材料与复合材料的优化摩尔质量比,进一步以该复合磁热材料为工质构建回热式Ericsson和Brayton制冷循环,基于热力学分析和数值计算,比较这两种制冷循环的非平衡回热量、净制冷量及性能系数等重要热力学参量,同时将复合材料的相关结果与单组分磁热材料的加以对比,结果表明:复合材料的大磁熵变温区要比任何一种组分材料的宽得多,而以复合材料为工质的制冷循环的净制冷量在近15 K温区内都较大,所得结果能为室温磁制冷机的参数优化设计提供有益的参考。 相似文献
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R. Bjørk C.R.H. Bahl A. Smith D.V. Christensen N. Pryds 《Journal of magnetism and magnetic materials》2010,322(21):3324-3328
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration. 相似文献
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Magnetocaloric effect and magnetic refrigeration 总被引:2,自引:0,他引:2
Vitalij K. Pecharsky Karl A. Gschneidner Jr. 《Journal of magnetism and magnetic materials》1999,200(1-3)
The phenomenon of the magnetocaloric effect along with recent progress and the future needs in both the characterization and exploration of new magnetic refrigerant materials with respect to their magnetocaloric properties are discussed. Also the recent progress in magnetic refrigerator design is reviewed. 相似文献
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J.A. Lozano M.P. Kostow E. Brück J.C. de Lima A.T. Prata P.A.P. Wendhausen 《Journal of magnetism and magnetic materials》2008,320(14):e189-e192
The powder metallurgy technique has been exploited as a means to prepare porous magnetocaloric materials. The alloy Mn1.1Fe0.9P0.46As0.54 was previously synthesized by mechanical alloying followed by a solid-state reaction for crystallization and homogenization. Subsequently, the alloy was comminuted and sintered at 1298 K. The obtained sintered product is aimed to be tested in a magnetic regenerator of a prototype machine. 相似文献
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A new model of a quantum refrigeration cycle composed of two adiabatic and
two isomagnetic field processes is established. The working substance in the
cycle consists of many non-interacting spin-1/2 systems. The performance of
the cycle is investigated, based on the quantum master equation and
semi-group approach. The general expressions of several important
performance parameters, such as the coefficient of performance, cooling
rate, and power input, are given. It is found that the coefficient of
performance of this cycle is in the closest analogy to that of the classical
Carnot cycle. Furthermore, at high temperatures the optimal relations of the
cooling rate and the maximum cooling rate are analysed in detail. Some
performance characteristic curves of the cycle are plotted, such as the
cooling rate versus the maximum ratio between high and low ``temperatures'
of the working substances, the maximum cooling rate versus the ratio between
high and low ``magnetic fields' and the ``temperature' ratio between high
and low reservoirs. The obtained results are further generalized and
discussed, so that they may be directly applied to describing the performance
of the quantum refrigerator using spin-$J$ systems as the working substance.
Finally, the optimum characteristics of the quantum Carnot and Ericsson
refrigeration cycles are derived by analogy. 相似文献
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