Performance Assessment and Layer Fraction Optimization of Gd–Y Multilayer Regenerators for Near Room-Temperature Magnetic Cooling

2020 ◽  
Vol 28 (03) ◽  
pp. 2050027 ◽  
Author(s):  
Henrique N. Bez ◽  
Alan T.D. Nakashima ◽  
Gusttav B. Lang ◽  
Bruno S. de Lima ◽  
Antonio J.S. Machado ◽  
...  
Keyword(s):  
Figure Of Merit ◽  
Room Temperature ◽  
Entropy Change ◽  
Cooling Power ◽  
Reasonable Accuracy ◽  
One Dimensional ◽  
Magnetic Cooling ◽  
Refrigerant Capacity ◽  
Adiabatic Temperature Change ◽  
Numerical Assessment

An experimental and numerical assessment of multilayer active magnetic regenerators (AMR) composed of gadolinium (Gd) and gadolinium–yttrium (Gd–Y) alloys (Gd[Formula: see text]Y[Formula: see text], Gd[Formula: see text]Y[Formula: see text] and Gd[Formula: see text]Y[Formula: see text]) is presented. First, by calculating the adiabatic temperature change and the isothermal entropy change from the experimental data for the above materials, we show that, with reasonable accuracy for engineering design purposes, these properties can be determined by shifting the properties of pure Gd to the Curie temperature of the Gd–Y alloy — a common but not yet validated assumption in the design of Gd–Y AMRs with a low Y content. Next, we show that the optimal Gd–Y layer fraction in multilayer AMRs can be determined using the figure of merit known as the material refrigerant capacity (RC), which agrees well with the results from a more complex one-dimensional thermal non-equilibrium porous medium AMR model. Finally, the performance of the latter model is verified against the experimental cooling power data for two- and three-layer Gd–Y regenerators at temperature spans of 25, 30 and 35[Formula: see text]K.

Refrigerant Capacity and Magnetocaloric Effect on LaFe11.1Co0.8Si1.1BX Alloys

2011 ◽  
Vol 84-85 ◽  
pp. 667-670
Author(s):  
Guo Qiu Xie
Keyword(s):  
Magnetocaloric Effect ◽  
Room Temperature ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
Field Change ◽  
Refrigerant Capacity ◽  
Structure Phase ◽  
Magnetic Field Change ◽  
Cubic Structure

In this paper, we report on the structure, magnetic properties and magnetocaloric effect in NaZn13-type LaFe11.1Co0.8Si1.1Bxalloys close to room temperature. The stable NaZn13cubic structure phase (space group isFm-3c) can easily obtained by annealing at 1080 °C for 225 hours. The maximal values of magnetic entropy change for LaFe11.1Co0.8Si1.1Bx(x=0.2, 0.25) were found to be 5.3 and 5.9 J/kg K at Curie temperature for a magnetic field change in 0-1.5 T, respectively. The calculated refrigerant capacity for a field change in 0–1.5 T is about 147 and 107 J/kg K, for LaFe11.1Co0.8Si1.1B0.2and LaFe11.1Co0.8Si1.1B0.25respectively, which is as larger as those of Gd(99.3%) alloy

Field Dependence of the Refrigerant Capacity for La0.6Ca0.4MnO3 Manganite

2009 ◽  
Vol 154 ◽  
pp. 163-168 ◽  
Author(s):  
R.A. Szymczak ◽  
Aleksandra Kolano-Burian ◽  
Roman Kolano ◽  
R. Puzniak ◽  
V.P. Dyakonov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Curie Temperature ◽  
Statistical Model ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Relative Cooling Power ◽  
Cooling Power ◽  
Magnetic Entropy ◽  
Refrigerant Capacity ◽  
Jahn Teller

The magnetocaloric effect in La0.6Ca0.4MnO3 manganite has been investigated. The isothermal magnetization versus applied magnetic field at various temperatures in the vicinity of Curie temperature was measured, and the temperature dependence of magnetic entropy change was determined using Maxwell’s relation. This value is comparable to that in Gd. Nevertheless, the relative cooling power of La0.6Ca0.4MnO3 was shown to be considerably lower than that of Gd. The experimental results have been analyzed in frames of a phenomenological statistical model. This model considers explicitly Jahn-Teller interactions and allows prediction of the field dependences of the magnetic entropy change and the relative cooling power.

scholarly journals Structural, magnetic and electrical properties of a new double-perovskite LaNaMnMoO 6 material

2017 ◽  
Vol 4 (11) ◽  
pp. 170920 ◽  
Author(s):  
Sameh Megdiche Borchani ◽  
Wissem Cheikh-Rouhou Koubaa ◽  
Makrem Megdiche
Keyword(s):  
Applied Field ◽  
Room Temperature ◽  
Double Perovskite ◽  
Entropy Change ◽  
Cooling Power ◽  
Room Temperature Resistivity ◽  
Ferromagnetic Transition ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Xrd Patterns

Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO 6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature T C is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO 6 sample as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of T C , |−ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg −1  K −1 . Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A 2 FeMoO 6 (A = Sr, Ba) double-perovskite system.

Numerical Simulation of Magnetic Cooling Cycles

2012 ◽  
Vol 190 ◽  
pp. 319-322
Author(s):  
Konstantin Skokov ◽  
Alexey Karpenkov ◽  
Yury G. Pastushenkov ◽  
Oliver Gutfleisch
Keyword(s):  
Numerical Simulation ◽  
Room Temperature ◽  
Magnetic Refrigeration ◽  
Cooling Power ◽  
Theoretical Limit ◽  
Magnetic Cooling

A model for Brayton cooling cycles used in magnetic refrigeration near room temperature was developed. This model was used to calculate a theoretical limit of temperature span and cooling power. The cooling power was calculated for single and double Brayton cooling cycles with Gd as the working body. The obtained results clearly demonstrate the functional ranges of Bryton-cycle refrigerators.

Iron Oxide-based Magnetic Nanoparticles for High Temperature Span Magnetocaloric Applications

2014 ◽  
Vol 1708 ◽  
Author(s):  
V. Chaudhary ◽  
R. V. Ramanujan
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Magnetic Nanoparticles ◽  
Room Temperature ◽  
Magnetic Entropy Change ◽  
Average Crystallite Size ◽  
Entropy Change ◽  
Superparamagnetic Nanoparticles ◽  
Cooling Power ◽  
Magnetic Entropy

ABSTRACTThe magnetocaloric effect of chemically synthesized Mn0.3Zn0.7Fe2O4 superparamagnetic nanoparticles with average crystallite size of 11 nm is reported. The magnitude of the magnetic entropy change (ΔSM), calculated from magnetization isotherms in the temperature range of 30 K to 400 K, increases from - 0.16 J-kg-1K-1 for a field of 1 T to - 0.88 J-kg-1K-1 for 5 T at room temperature. Our results indicate that ΔSM values are much higher than primarily reported values for this class of nanoparticles. ΔSM is not limited to the ferromagnetic-paramagnetic transition temperature; instead, it occurs over a broad range of temperatures, resulting in high relative cooling power.

scholarly journals Theoretical Investigation of the Electrocaloric Properties of Lead-free Ferroelectric Ceramic

2020 ◽  
Author(s):  
Hend Kacem ◽  
Ahmad Dhahri ◽  
Mohamed Amara GDAIEM ◽  
Z. SASSI ◽  
L. SEVEYRAT ◽  
...  
Keyword(s):  
Ferroelectric Phase Transition ◽  
Room Temperature ◽  
Ferroelectric Phase ◽  
Entropy Change ◽  
Ferroelectric Ceramic ◽  
Solid State Reaction Method ◽  
Cooling Power ◽  
Promising Candidate ◽  
Theoretical Approaches ◽  
P4mm Space Group

Abstract BaTi0.91Sn0.09O3 (BST) sample was prepared by the solid-state reaction method. The structural, morphological and electrocaloric properties were studied. The sample crystallized in the tetragonal structure with P4mm space group. Based on mapping image, the sensitivity and spatial resolution of the different elements in our sample were improved. According to the variation of polarization as function of temperature, our sample had a paraelectric-ferroelectric phase transition, around room temperature. The electrocaloric properties of our sample were investigated using theoretical approaches. The important parameters such as maximum entropy change, relative cooling power and full width at half maximum were explained qualitatively. These results make our sample promising candidate for refrigeration domain.

scholarly journals Solid-state cooling by elastocaloric polymer with uniform chain-lengths

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Shixian Zhang ◽  
Quanling Yang ◽  
Chenjian Li ◽  
Yuheng Fu ◽  
Huaqing Zhang ◽  
...  
Keyword(s):  
Solid State ◽  
Conformational Changes ◽  
Room Temperature ◽  
Entropy Change ◽  
Cooling Device ◽  
Elastocaloric Effect ◽  
Adiabatic Temperature Change ◽  
Cooling Devices ◽  
Chain Lengths ◽  
Solid State Cooling

AbstractAlthough the elastocaloric effect was found in natural rubber as early as 160 years ago, commercial elastocaloric refrigeration based on polymer elastomers has stagnated owing to their deficient elastocaloric effects and large extension ratios. Herein, we demonstrate that polymer elastomers with uniform molecular chain-lengths exhibit enormous elastocaloric effects through reversible conformational changes. An adiabatic temperature change of −15.3 K and an isothermal entropy change of 145 J kg−1 K−1, obtained from poly(styrene-b-ethylene-co-butylene-b-styrene) near room temperature, exceed those of previously reported elastocaloric polymers. A rotary-motion cooling device is tailored to high-strains characteristics of rubbers, which effectively discharges the cooling energy of polymer elastomers. Our work provides a strategy for the enhancement of elastocaloric effects and could promote the commercialization of solid-state cooling devices based on polymer elastomers.

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

scholarly journals A 2.1 GHz, 210 μW, —189 dBc/Hz DCO with Ultra Low Power DCC Scheme

Electronics ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 805
Author(s):  
Shi Zuo ◽  
Jianzhong Zhao ◽  
Yumei Zhou
Keyword(s):  
Low Power ◽  
Current Efficiency ◽  
Phase Noise ◽  
Duty Cycle ◽  
Semiconductor Manufacturing ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Cmos Process ◽  
Ultra Low Power ◽  
Measured Phase

This article presents a low power digital controlled oscillator (DCO) with an ultra low power duty cycle correction (DCC) scheme. The DCO with the complementary cross-coupled topology uses the controllable tail resistor to improve the tail current efficiency. A robust duty cycle correction (DCC) scheme is introduced to replace self-biased inverters to save power further. The proposed DCO is implemented in a Semiconductor Manufacturing International Corporation (SMIC) 40 nm CMOS process. The measured phase noise at room temperature is −115 dBc/Hz at 1 MHz offset with a dissipation of 210 μμW at an oscillating frequency of 2.12 GHz, and the resulin figure-of-merit is s −189 dBc/Hz.

Numerical assessment on the performance of variable area single- and two-stage ejectors: A comparative study

2021 ◽  
pp. 095440892110331
Author(s):  
Anil Kumar ◽  
Virendra Kumar ◽  
PMV Subbarao ◽  
Surendra K Yadav ◽  
Gaurav Singhal
Keyword(s):  
Change Theory ◽  
Single Stage ◽  
Two Stage ◽  
Entrainment Ratio ◽  
Ansys Fluent ◽  
One Dimensional ◽  
Flow Parameters ◽  
Constant Rate ◽  
Numerical Assessment ◽  
The One

The two-stage ejector has been suggested to replace the single-stage ejector geometrical configuration better to utilize the discharge flow’s redundant momentum to induce secondary flow. In this study, the one-dimensional gas dynamic constant rate of momentum change theory has been utilized to model a two-stage ejector along with a single-stage ejector. The proposed theory has been utilized in the computation of geometry and flow parameters of both the ejectors. The commercial computational fluid dynamics tool ANSYS-Fluent 14.0 has been utilized to predict performance and visualize the flow. The performance in terms of entrainment ratio has been compared under on- design and off-design conditions. The result shows that the two-stage ejector configuration has improved (≈57%) entrainment capacity than the single-stage ejector under the on-design condition.

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