Influence of manganite powder grain size and Ag-particle coating on the magnetocaloric effect and the active magnetic regenerator performance

Turcaud, J.A.; Bez, Henrique Neves; Ruiz‐Trejo, Enrique; Bahl, Christian; Nielsen, Kaspar Kirstein; Smith, Anders; Cohen, L. F.

doi:10.1016/j.actamat.2015.06.058

Cited by 11 publications

(3 citation statements)

References 31 publications

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“…Due to reasons described in section Regenerator Stability, only regenerators #3 and #4 were tested successfully in the active test machine. Since the mass of each regenerator is small (∼30 g), the absolute values of the temperature span are small in comparison to other results from the same AMR device (Bahl et al, 2012;Turcaud et al, 2015). However, the results shown in Figure 8 are valid for comparable studies of the regenerators discussed here.…”

Section: Active Cooling Performance Comparisonmentioning

confidence: 52%

Characterization of Freeze-Cast Micro-Channel Monoliths as Active and Passive Regenerators

et al. 2020

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The efficiency of the magnetic refrigeration process strongly depends on the heat transfer performance of the regenerator. As a potential way to improve the heat transfer performance of a regenerator, the design of sub-millimeter hydraulic diameter porous structures is realized by freeze-cast structures. Four freeze-cast regenerators with different pore widths are characterized experimentally and numerically. Empirical parameters are determined for the correlations of heat transfer and flow resistance via a 1D model. Thermal effectiveness and pressure drop are measured for thermal-hydraulic evaluations. Temperature span and specific cooling capacity are obtained to compare the magnetocaloric potential based on the material La0.66Ca0.27Sr0.06Mn1.05O3. The stability of freeze-cast regenerators is validated by comparing the performance during, before and after oscillatory flow and periodic magnetic field tests. Smaller pore design obtain the better heat transfer performance and required mechanical strength, while pore design with significant dendrites provides the worst tradeoff between heat transfer performance and flow resistance.

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Section: Active Cooling Performance Comparisonmentioning

confidence: 52%

Characterization of Freeze-Cast Micro-Channel Monoliths as Active and Passive Regenerators

et al. 2020

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“…(B8) to Eq. (B9), 𝑇 ̅ 𝑠,ℎ − 𝑇 ̅ 𝑠,𝑐 ≈ 𝑇 ̅ 𝑓,ℎ − 𝑇 ̅ 𝑓,𝑐 ≈ ∆𝑇 ℎ𝑐 is assumed, which is ascribed to 1) the thermal conductivity of MCM being normally sufficiently small (1-15 Wm -1 K -1 , [67][68][69][70][71]) to maintain similar solid and fluid temperature gradients and 2) the solid-liquid temperature difference being small for well-designed regenerators. Similar process can be applied to deduce the effectiveness during hot-to-cold blow (𝜀 ℎ ),…”

Section: 𝜑 = 𝜒mentioning

confidence: 99%

Heat transfer figures of merit for mapping passive regenerator performance to active regenerator cooling power

Liang

Nielsen

Engelbrecht

et al. 2020

Applied Thermal Engineering

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“…Although currently scandia is a relatively expensive material, ScSZ's growing use as electrolyte in solid oxide fuel cells may lower its price. 14 The use of Tollens' reagent to fabricate metal ceramic composites for a variety of purposes has been reported recently in applications such as oxygen separation, 5 methane reforming, 15 hydrogen separation, 16 magnetic refrigeration 17 and anode fabrication. 18,19 In this work, the composite membrane fabrication is presented in detail that allows reproducibility and it is followed by characterization by SEM, XRD and conductivity tests.…”

mentioning

confidence: 99%

Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites

Ruiz‐Trejo¹,

Bertei²,

Maserati³

et al. 2017

J. Electrochem. Soc.

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Dense composites of silver and Sc-stabilized ZrO 2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens' reagent. A composite with 8.6 vol % of silver exhibits metallic conductivity of 186 S cm −1 and oxygen flux of 0.014 μmol cm −2 s −1 at 600 • C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample (Ag 4.7 vol%) is analyzed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and Ag, yet small silver particles on the surface improve the reduction of oxygen. Oxygen reduction is highly promoted by silver on the surface and there are no limitations of charge transfer at the interface between silver and ScSZ. The capability of metallic silver to reduce oxygen has been long known and recorded since Lucas reported it to Dalton as early as 1818 1 but better understood and quantified over the last 50 years. 2,3This particular capability of silver can be exploited to incorporate oxygen into a solid system, be it a solid oxide fuel cell cathode 4 or an oxygen separation membrane. 5 Oxygen can be separated from air using a double phase membrane with an oxygen-ion conductor, e.g. scandia stabilized zirconia, and an electronic conductor, such as silver, that acts as a very efficient oxygen reducing agent. Scandia stabilized zirconia is known to have higher conductivity than yttria stabilized zirconia since it was first reported in 1900 by Nernst 6 but identified as an oxygen ion conductor by Wagner 7 several decades later. The use of double-phase metal ceramic composites to separate oxygen from air was first described by Mazanec, 8 who mixed Pd or Pt with YSZ and used the composite to drive chemical reactions. Although feasible, this approach normally requires large amounts of expensive metal to achieve percolation, ranging from 30 to 50 vol %, so that composite membranes cannot compete with the high oxygen flux reported in single phase perovskites, such as those reported by Teraoka 9 in 1985. To date, most of the research in high temperature oxygen separation is still performed in mixed ionic electronic conductive perovskites ABO 3 , where A is one or more lanthanides and/or alkaline earths and B one or more transition metal oxides, for example Nonetheless, these materials have two persistent problems: the high operating temperatures (>800 • C) and the unsatisfactory chemical and mechanical stability in operating conditions. Furthermore, the chemical composition of the material affects both the stability and the oxygen sepa...

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Influence of manganite powder grain size and Ag-particle coating on the magnetocaloric effect and the active magnetic regenerator performance

Cited by 11 publications

References 31 publications

Characterization of Freeze-Cast Micro-Channel Monoliths as Active and Passive Regenerators

Characterization of Freeze-Cast Micro-Channel Monoliths as Active and Passive Regenerators

Heat transfer figures of merit for mapping passive regenerator performance to active regenerator cooling power

Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites

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