Innovative design of a magnetocaloric system

Vasile, Carmen; Müller, Christian

doi:10.1016/j.ijrefrig.2006.07.016

Cited by 57 publications

(21 citation statements)

References 12 publications

(12 reference statements)

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“…The researchers from the University of Applied Sciences of Western Switzerland exhibited the prototype at the industrial fair in Hannover and won first prize at the Swiss Technology Awards 2006. [52,53]. Unfortunately, no data regarding the prototype's performance was given at that point.…”

Section: Swiss Prototypesmentioning

confidence: 99%

Overview of Existing Magnetocaloric Prototype Devices

Kitanovski

Tušek

Tomc

et al. 2014

Magnetocaloric Energy Conversion

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Since Brown [1] built the first magnetic refrigerator prototype working near room temperature in 1976 there has been a large number of different prototypes [2] designed and built over the past 40 years. However, despite there being 4 decades of scientific input into the field of magnetocaloric energy conversion near room temperature, the technology is only now at the brink of commercialization. With every new prototype that is built, we see slow but measureable improvements toward the desired goal. Figure 7.1 shows the number of prototypes built until 2014. It is clear that the number of prototypes increases with each new year, pointing to the fact that the magnetocaloric energy conversion research community is expanding research activities together with the S-curve of technology development.The reasons why magnetocaloric technology near room temperature is only now slowly becoming market-ready lie in the fact that there are a number of different obstacles regarding the device's design, which need to be overcome before finalizing the idea of commercializing magnetocaloric technology. Addressing all the design issues is, of course, a difficult task. With each prototype built researchers try to solve different design issues, ranging from the heat-transfer problems of the AMRs and the working fluids, the design issues of the AMRs and magnet assemblies, to the problems related to peripheral elements, such as pump and valves systems. In this manner, each prototype built up until now has its own special feature. Each of them is trying to address one or more of the engineering barriers, but almost never a system as a whole.However, there is one major characteristic that can be distinguished for all the existing prototypes. There are two groups of devices, i.e. the ones operating in a reciprocating (linear motion) manner and the others operating in a rotary manner. The reciprocating and rotary operations of the magnetocaloric device are more or less related to the way how the AMR is exposed to the alternating magnetic field, as is described in Chap. 4 on Active Magnetic Regeneration (see also Chap. 8). One possibility is to move the AMR or the magnet in a reciprocal direction back and forth, and the other is to rotate the AMR or the magnet. As you will see in the following sections, each of the two methods has its pros and cons, depending on the functionality of the device. Is it an experimental testing device? Or is it a real

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Section: Swiss Prototypesmentioning

confidence: 99%

Overview of Existing Magnetocaloric Prototype Devices

Kitanovski

Tušek

Tomc

et al. 2014

Magnetocaloric Energy Conversion

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“…In 2006, Vasile and Muller [43] presented a paper in which a Halbach structure, embodied with the soft iron, was shown. Such a principle enables better shielding of the magnetic flux than the previous case.…”

Section: Static Halbach (2d) Magnet Assembliesmentioning

confidence: 99%

“…However, in both cases the magnetic Fig. 3.32 a An example of a static magnet assembly developed by Lee et al [42], b an example of a part of the magnet assembly developed by Vasile and Muller [43] shielding is not provided in a direction that is perpendicular to the surface plane of the magnet (direction of observer of Fig. 3.32).…”

Section: Static Halbach (2d) Magnet Assembliesmentioning

confidence: 99%

Magnetic Field Sources

Kitanovski

Tušek

Tomc

et al. 2014

Magnetocaloric Energy Conversion

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In this chapter we describe some of the most important issues that relate to the sources for magnetic fields. We will try to provide information for engineers about the different possible magnetic field sources with respect to their application in magnetocaloric energy conversion. However, the main emphasis will be on permanent magnets and their assemblies. This is due to the fact that other kinds of magnetic field sources, for instance, electric resistive coils (electromagnets) operate with a rather low efficiency. The efficiency in electromagnets in terms of thermodynamics must be considered as the ratio of the energy output (magnetization energy) and the energy input to the coil. The current passing through the coiled wires in an electromagnet will induce Joule heating, due to the electric resistance. Not only will a loss of valuable energy occur, but the magnetic field source will, in most cases, also require cooling, especially in cases where a high magnetic flux density is required. In superconducting magnets, which can be treated as a special class of electromagnets, the current may be kept circulating through the wires of a coil without electrical resistance losses. However, in order to keep the superconducting magnet operating, a cryogenic system is required to provide cooling for the superconducting electrical coils. Namely, there is no practical application of a room-temperature superconducting material. There are, however, some indicators that this could be possible [1][2][3][4][5]. And if this happens in future, this chapter will unfortunately (or fortunately) not be of much use, but the application will open up an unbelievable range of applications, which will certainly change our way of life, including magnetocaloric energy conversion.The reader should note that the magnetic field source is the most expensive part of a magnetic refrigerator or a heat pump, especially if those are based on permanent or superconducting magnets. Therefore, the optimal design of a magnetic field source is crucial for obtaining a cost-effective and energy-efficient device.

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“…The rotary magnetic refrigeration devices mentioned earlier, Refs. [11], [13], [14] and [15] have Λ cool = 0.13, 0.11, 0.21 and 0.03 respectively. For this particular design the choice of the high and low flux density regions is rather arbitrary and so they could have been chosen to span less than 45 degree.…”

Section: Performance Of the Magnetmentioning

confidence: 99%

An optimized magnet for magnetic refrigeration

Bjørk

Bahl

Smith

et al. 2010

Journal of Magnetism and Magnetic Materials

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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.

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Innovative design of a magnetocaloric system

Cited by 57 publications

References 12 publications

Overview of Existing Magnetocaloric Prototype Devices

Overview of Existing Magnetocaloric Prototype Devices

Magnetic Field Sources

An optimized magnet for magnetic refrigeration

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