Performance analysis of a rotary active magnetic refrigerator

Lozano, Jaime; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein; Eriksen, Dan; Olsen, Ulrik Lund; Barbosa, Jader R.; Smith, Anders; Prata, A. T.; Pryds, Nini

doi:10.1016/j.apenergy.2013.05.039

Cited by 73 publications

(30 citation statements)

References 29 publications

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“…4.5 for different AMR thermodynamic cycles. The theoretical results usually show a linear-like dependence of the cooling power and temperature span (for magnetocaloric materials with the second-order phase transition), while the experimentally measured dependence is more complex mostly due to losses to the surroundings [92,110].…”

Section: The Impact Of the Operational Parameters And Geometry On Thementioning

confidence: 95%

“…Thermal interactions with the regenerator housing and parasitic losses to the surroundings are therefore ignored. However, it was shown [92,110] that they have a significant effect when modelling a real AMR device (and predicting its performance). There are two general approaches for including the thermal interactions with the surroundings into the AMR model: directly into the governing equations [47,50] or through an iterative thermal analysis where the estimated loss of cooling power for particular operating conditions (through Eq.…”

Section: Heat Losses To the Surroundingsmentioning

confidence: 97%

“…There are two general approaches for including the thermal interactions with the surroundings into the AMR model: directly into the governing equations [47,50] or through an iterative thermal analysis where the estimated loss of cooling power for particular operating conditions (through Eq. 4.25) is used as an input for the model [92,110]. The direct approach applies additional terms in the AMR governing equations (Eqs.…”

Section: Heat Losses To the Surroundingsmentioning

confidence: 99%

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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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Section: The Impact Of the Operational Parameters And Geometry On Thementioning

confidence: 95%

Section: Heat Losses To the Surroundingsmentioning

confidence: 97%

Section: Heat Losses To the Surroundingsmentioning

confidence: 99%

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Active Magnetic Regeneration

Kitanovski

Tušek

Tomc

et al. 2014

Green Energy and Technology

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“…The decrease in performance is mainly due to the friction in the AMR rotation and the poorer heat transfer at higher operating frequencies. In 2013 Lozano et al [64] presented further performance studies on this prototype [63]. They studied the influence of different parasitic losses (in filter, tubes, flow-head and regenerator) in relation to different temperatures at the cold side.…”

Section: Danish Prototypesmentioning

confidence: 98%

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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“…Measured properties of a sample of commercial grade Gd were integrated in the models as by Lozano et al (2013). Particularly, ܿ and ‫ݏ߲‬ ߲ߤ ‫ܪ‬ ⁄ are a function of the regenerator temperature and the internal magnetic field.…”

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confidence: 99%

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

Torregrosa-Jaime

Corberán

Payá

et al. 2015

International Journal of Refrigeration

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A one-dimensional model of a parallel-plate active magnetic regenerator (AMR) is presented in this work. The model is based on an efficient numerical scheme which has been developed after analysing the heat transfer mechanisms in the regenerator bed. The new finite difference scheme optimally combines explicit and implicit techniques in order to solve the one-dimensional conjugate heat transfer problem in an accurate and fast manner while ensuring energy conservation. The present model has been thoroughly validated against passive regenerator cases with an analytical solution. Compared to the fully implicit scheme, the proposed scheme achieves more accurate results, prevents numerical errors and requires less computational effort. In AMR simulations the new scheme can reduce the computational time by 88%.

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Performance analysis of a rotary active magnetic refrigerator

Cited by 73 publications

References 29 publications

Active Magnetic Regeneration

Active Magnetic Regeneration

Overview of Existing Magnetocaloric Prototype Devices

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

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