Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device

Moos, Lars von; Nielsen, Kaspar Kirstein; Engelbrecht, Kurt

doi:10.1016/j.ijrefrig.2013.05.005

Cited by 19 publications

(7 citation statements)

References 4 publications

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“…This degradation ("fatigue") is surely detrimental to any cooling applications. Similar issues have attracted much more attention for magnetocaloric refrigeration, 12,[89][90][91][92][93][94] while investigation on electrocaloric counterpart is in its infancy stage. [1][2][3][4][5][6][7][8][9][10][11][12] Quantitative analysis of contributions of thermal and electrical losses to the electrocaloric effect is of great importance especially for the design of electrocaloric prototype devices.…”

Section: E First-order Phase Transitionmentioning

confidence: 99%

“…94 For instance, control of heat flux direction in active magnetic regeneration in an effective manner can be very useful to enhance the operating frequency and thus the power density of the device. 158 Direct thermal mapping captured by IR camera allows analyzing qualitatively the dynamic heat flux in one specific prototype device according to distributions of adiabatic temperature change.…”

Section: Infra-red Cameramentioning

confidence: 99%

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Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Liu

Scott

Dkhil

2016

Applied Physics Reviews

234

150

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It has been ten years since the discovery of the giant electrocaloric effect in ferroelectric materials showed that it is possible to employ this effect for substantial cooling applications. This last decade has been marked by increasing research interest, especially in characterizing and measuring the electrocaloric effect using both the so-called indirect and direct approaches. In this context, a comprehensive summary and careful reexamination of these approaches are very timely and of great importance to justify the assumptions used in different measurement techniques. This review is therefore dedicated to cover recent important and rapid advances from both the indirect and direct measurements and provides critical insights relevant for quantifying the electrocaloric effect. It involves electrocaloric materials from normal ferroelectrics, antiferroelectrics, and relaxors, and it fundamentally focuses on how the electrocaloric entropy changes in response to electric field in these typical electrocalorics. The article addresses recent developments, especially during the past three years, such as technical selection of proper polarization-electric field loops, negative electrocaloric effect in antiferroelectrics and relaxors, the controversial debate on the indirect method in relaxors, the important role of field dependence of specific heat, kinetic factors, and so on. Moreover, this review also is concerned with extracting reliable data by direct measurements. Four typical techniques and devices used recently, such as thermocouples, differential scanning calorimeters, specifically designed calorimeters, and scanning thermal microscopy, are briefly reviewed, while infrared cameras are emphasized. We hope that our review will not only provide a useful background to understand fundamentally the electrocaloric effect and what one really measures but also may act as a practical guide to exploit and develop electrocalorics towards the design of suitable devices. Published by AIP Publishing. [http://dx

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Section: E First-order Phase Transitionmentioning

confidence: 99%

Section: Infra-red Cameramentioning

confidence: 99%

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Liu

Scott

Dkhil

2016

Applied Physics Reviews

234

150

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“…Mn-Fe, La-Fe-Si). It was shown that hysteresis behaviour can drastically reduce the magnetocaloric effect under the cyclic conditions applied in the AMR as well as the AMR performance [112,113]. To the best of our knowledge, there is no AMR model that directly applies the hysteresis of the magnetocaloric material.…”

Section: Hysteresis Lossesmentioning

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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“…This can drastically reduce the MCE during the cycling operation as well as the efficiency of the magnetocaloric device. The impact of the hysteresis on the performance of the magnetic refrigerator can be found in [34,35].…”

Section: Near-zero Hysteresis Of the Magnetocaloric Effectmentioning

confidence: 99%

Magnetocaloric Materials for Freezing, Cooling, and Heat-Pump Applications

Kitanovski

Tušek

Tomc

et al. 2014

Magnetocaloric Energy Conversion

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Magnetocaloric materials (MCM) are the 'heart' of every magnetic refrigeration or heat-pump application. Apart from having a crucial role in the heat-regeneration process, they also exhibit a special and vital phenomenon for magnetic refrigeration called the magnetocaloric effect. As mentioned in the previous chapter on the Thermodynamics of magnetocaloric energy conversion and as described later in the book in the Chap. 7 (Overview of existing magnetocaloric prototype devices) the first real magnetic devices working near room temperature were not built until the middle of the 1970s. However, the discovery of the magnetocaloric effect (MCE) in ferromagnetic materials dates back more than 90 years to 1917.The MCE was discovered by the French and Swiss physicists Weiss and Piccard [1,2]. This is an important historical fact that needs to be emphasized, since in the past 15 years a misconception has arisen in the magnetocaloric research community, wrongly attributing the discovery of the MCE to the work of Warburg [3]. At this point we have to address the recent paper of Smith [4], who did a thorough and interesting review of the research on thermodynamics that led to the discovery of the MCE. The next few lines are a brief summary of the historical events according to Smith's findings. He reviewed the original works of scientists that date back to the nineteenth century, starting with Joule in 1843 [5]. Joule observed that heat was evolved from iron samples when they were subjected to a magnetic field. Later, in 1860, Thomson (Lord Kelvin) [6] was already aware of the fact that ferromagnetic materials lose their magnetic properties when heated above a certain temperature (now known as the Curie temperature). Thomson correctly predicted that ferromagnetic materials would experience a heating effect when magnetized and a cooling effect when demagnetized, and that these effects would be the largest around the temperature where they lose their magnetization. However, he did not associate these predictions with the magnetocaloric effect. Then, in 1881, Warburg published a paper [3], which is nowadays wrongly cited when referencing the discovery of the MCE. Nevertheless, the work of Warburg was of great significance, since he was the first to explain magnetic hysteresis. He correctly predicted that the magnetization of a material is larger when the magnetic field is decreasing than when it is increasing. One year later, in 1882, Ewing [7] discovered the same phenomenon and was the first to name it "hysteresis". It was not until the works of

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Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device

Cited by 19 publications

References 4 publications

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

Active Magnetic Regeneration

Magnetocaloric Materials for Freezing, Cooling, and Heat-Pump Applications

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