Thermodynamic Considerations for the Design of Active Magnetic Regenerative Refrigerators

Hall, J. L.; Reid, C. E.; Spearing, Ian G.; Barclay, J. A.

doi:10.1007/978-1-4613-0373-2_208

Cited by 20 publications

(9 citation statements)

References 4 publications

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“…When the steadystate is reached, there is a nearly linear temperature profile i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 1 ( 2 0 0 8 ) 4 3 2 -4 4 3 through the regenerator going from the CHEX (T C ) to the HHEX (T H ). The AMR constitutes a thermodynamic system which can neither be represented by analogies to regenerative vapour-compression refrigeration cycles nor as a composite of cascaded sub-cycles (Hall et al, 1996). Each infinitesimal element of the regenerator experiences a unique thermodynamic cycle where a solid produces the refrigeration while a fluid transfers heat between the regenerator elements.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator

Petersen

Pryds

Smith

et al. 2008

International Journal of Refrigeration

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Section: Introductionmentioning

confidence: 99%

Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator

Petersen

Pryds

Smith

et al. 2008

International Journal of Refrigeration

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“…Indeed it has been suggested that for an ideal performance the magnetocaloric effect of the regenerator should obey just this constraint. 18 The results presented here show that for most materials this is a valid assumption. FIG.…”

Section: Discussionmentioning

confidence: 52%

Constraints on the adiabatic temperature change in magnetocaloric materials

2010

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The thermodynamics of the magnetocaloric effect implies constraints on the allowed variation in the adiabatic temperature change for a magnetocaloric material. An inequality for the derivative of the adiabatic temperature change with respect to temperature is derived for both first-and second-order materials. For materials with a continuous adiabatic temperature change as a function of temperature, this inequality is shown to hold for all temperatures. However, discontinuous materials may violate the inequality. We compare our results with measured results in the literature and discuss the implications of the result. Similar inequalities hold for barocaloric and electrocaloric materials.

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“…As explained in Hall et al [11], the major difference between an AMR and a cascade cycle is in the fact that the AMR cycle does not pump heat directly between the next-neighbour particles, but all the particles accept or reject heat to the heattransfer fluid at the same time and are coupled indirectly through the working fluid. So, in the AMR cycle, there is no overlapping of the internal cycles at the same time, as is the case in cascade systems.…”

Section: Operation Of An Active Magnetic Regenerator (Different Thermmentioning

confidence: 99%

Active Magnetic Regeneration

Kitanovski

Tušek

Tomc

et al. 2014

Green Energy and Technology

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It is well known that the magnetocaloric effect of most magnetocaloric materials at moderate magnetic fields (up to 1.5 T) is limited to a maximum adiabatic temperature change of 5 K [1,2]. This value is not sufficient for such materials to be directly implemented into a practical cooling or heating device where temperature span over 30 K is required. Therefore, in order to increase the temperature span, one and so far the best option is for a heat regenerator to be included in the magnetic thermodynamic cycle.A heat regenerator is a type of indirect heat exchanger where the heat is periodically stored and transferred from/to a thermal storage medium (regenerative material) by a working (heat-transfer) fluid. The regenerative material usually has a porous structure, through which a working fluid is pumped in an oscillatory, counter-flow manner (which is more efficient than a parallel flow system). During the 'hot period', a warmer fluid flows through the regenerative material, which cools down, while the material heats up. As a result, heat is stored in the material. During the 'cold period', a cooler fluid flows through previously heated regenerative material, so the fluid heats up, while the material cools down. The heat is therefore transferred back to the fluid (the same fluid or a different one) at a different phase of the thermodynamic cycle. After a certain number of such steps, a periodic steady state is reached and, as a result, a temperature profile can be established along the length of the regenerator [3].The need to apply heat regenerators in a magnetic refrigerator was already realized by Brown [4] in the first prototype of a magnetic refrigerator, built in 1976. He applied a regenerative Stirling-like thermodynamic cycle (very similar to AMR), which significantly increased the temperature span of the device [4,5]. A few years later Steyert [6] and Barclay and Steyert [7] presented and explained the active magnetic regenerator, which remains the most applied method for the exploitation of the magnetocaloric effect at room temperature. Furthermore, all prototypes of magnetic refrigerators built since then have been based on the AMR process [5]. An AMR, unlike a passive (regular) heat regenerator, contains a magnetocaloric material as the regenerative material. It has a double function in a magnetic regenerator, i.e. it works as a regenerator and enables an increase in the temperature span as well as working as a coolant and generating/absorbing heat between the particular phases of the

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Thermodynamic Considerations for the Design of Active Magnetic Regenerative Refrigerators

Cited by 20 publications

References 4 publications

Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator

Two-dimensional mathematical model of a reciprocating room-temperature Active Magnetic Regenerator

Constraints on the adiabatic temperature change in magnetocaloric materials

Active Magnetic Regeneration

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