cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.thermag.2018.0041
title: Thermal performance mapping of microchannel active magnetic regenerator under oscillatory fluid flows.

description: The paper describes a computational model of the transient conjugated conductive heat transfer in magnetocaloric material (MCM) microchannel wall and convective heat transfer in fluid flow in channels. The model is solved using Ansys Fluent. The temperature span, transient variation of Nusselt number (Nu) and effect of the ratio of channel spacing to diameter (porosity) are examined. Heat transfer enhancement and AMR dimension optimization are presented. The present study focused on the mapping the thermal response of active magnetic regenerator made of different geometric configurations, materials and exposed to different heat transfer fluids. For microchannel regenerator, the ratio б/d which defines the porosity was seen to have significant effect of the achievable temperature span. The optimum performance was seen to be for a Biot number (Bi) values of below 0.1. For heat transfer fluids, liquid metals Galinstan and Sodium-Potassium (NaK) yielded higher temperature spans as compared to the water, however, their corresponding pumping power requirements were also higher.
DOI: 10.18462/iir.thermag.2018.0005
title: Fully solid state thermomagnetoelectric generator: cycle model and proof-of-concept results.

description: Electricity generation from heat in small-scale systems is currently limited to internal and external combustion heat engine generators or thermoelectric elements. This study introduces a new concept for a solid state thermomagnetoelectric power generator and presents a theoretical study of the cycle. While magnetocaloric materials (MCMs) are common in cryogenic cooling applications, in this work the magnetocaloric thermodynamic heat pump cycle is reversed to generate electricity from low-grade heat. A critical distinguishing feature of the approach is that there are no moving parts: the system directly converts heat into electricity with no moving magnet or regenerators (similar to thermoelectric elements). By periodic heating and cooling of the MCM, the magnetic field inside the copper coil changes in time, generating alternating current electricity. This fully solid state system can directly convert heat into electricity and is modeled at 54% of Carnot efficiency. Compared with state-of-the-art thermoelectric elements, the proposed technology has 3-4 times higher heat-to-electricity conversion efficiency at the same driving temperature difference.
DOI: 10.18462/iir.thermag.2018.0008
title: Recent experimental results of first order LaFeSi-based magnetocaloric materials in an Active Magnetic Regeneration device.

description: Recently, a lot of progress has been made by the community to optimise the properties of LaFeSi-based alloys in order to enable their integration into prototypes for different magnetocaloric applications. In this paper we present a set of experimental results obtained with a specific layering of materials having different Curie temperatures integrated into a rotating R&D prototype. Furthermore, two types of endurance tests were performed on those materials using a separate experimental test bench. The obtained results are promising and present the basis for a possible replacement of Gd-based alloys with first order LaFeSi-based alloys to be used in our ready-to-be-deployed magnetic refrigeration systems. LaFeSi-based alloys have the potential to increase the cooling power and reduce the cost of our units due to reduced raw material costs. This is a critical factor, which will make the technology more accessible for large-scale production.
DOI: 10.18462/iir.thermag.2018.0013
title: Experimental investigation of fifteen-layer epoxy-bonded La(Fe,Mn,Si)13Hy active magnetic regenerator.

description: We present the experimental results compared with numerical simulations of a fifteen-layer epoxy bonded regenerator with the first order phase transition material La(Fe,Mn,Si)13Hy. The maximum temperature span established at zero-load conditions was ΔTspan=15.4 K at U=0.5. The experimental investigation was conducted in a medium-scale rotary device at KTH Royal Institute of Technology. The La(Fe,Mn,Si)13Hy materials were bonded with 2.3 wt. % epoxy by Vacuumschmelze GmbH, Germany. The experimental results and numerical modeling are in good agreement.
DOI: 10.18462/iir.thermag.2018.0014
title: Thermodynamic parameters of a magnetic refrigerator with a Carnot cycle.

description: Theoretical modeling of thermodynamic and technical parameters of a cryogenic single-stage magnetic refrigerator operating at a temperature of about 25 K and in a magnetic field up to 10 T was carried out in the present work. As a working body, the alloy DyNi2 is used. Modeling of heat transfer processes with a single cooling cycle was carried out. The calculation showed that for a given design configuration, the average heat transfer time is not more than 1-2 seconds, then the entire time of a single cooling cycle is no more than 2-4 seconds. This allows one to estimate the specific power and the achieved temperature difference of a singlestage refrigerator with a Carnot cycle. An estimate for the coefficient of performance (COP) of the cooling process shows advantages over traditional refrigerators based on gaseous working bodies.
DOI: 10.18462/iir.thermag.2018.0017
title: Modelling and simulation of a Gd-based thermomagnetic motor.

description: The initial developments on thermomagnetic motors date from 1880's with the patents of Edison and Tesla. More recently, due to the developments on magnetic cooling systems and magnetocaloric materials around room temperature, research on thermomagnetic motors has gained interest. This work presents a theoretical modeling of a reciprocating thermomagnetic motor based on Tesla's concept. The mathematical model solves the solid energy equation and the finite volume method was implemented. Gd is used as magnetic material, and its magnetic properties are obtained from WDS model. The Gd block have the dimensions of 100x100x10mm. To warm up and cool down the Gd block, a hot and cold water streams, respectively, are considered. A magnetic field of 1.33 T is generated by a NdFeB magnetic circuit. The main results are the net force acting on the plate. Additional results for temperature distribution are presented.
DOI: 10.18462/iir.thermag.2018.0031
title: Experimental researches on the performance of a rotary-type magnetic refrigerator with double-Halbach permanent magnet arrays.

description: A room-temperature rotary-type magnetic refrigerator based on previous experiences is designed and constructed with a modified double-Halbach permanent magnet arrays. When the inner magnet array is periodically rotated, the average magnetic field provided by the new magnet system ranges from 0.04 T to 1.50 T in the centre region of the inner bore along 70% length of magnet arrays. This is fairly superior to the average value of previous magnetic arrays, which ranges from 0.3 T to 1.2 T. Influence of the magnetic field strength on the refrigerating performance have been discussed and studied. A series of experiments based on Gadolinium have been done to investigate the system performance including no-load temperature span and cooling power, with different frequencies and utilization factors.
DOI: 10.18462/iir.thermag.2018.0035
title: A numerical investigation upon the energy performances of caloric materials working in an Active Regenerator.

description: Over the years, experimental and numerical studies have consolidated the potential of the caloric cooling as a technology of tomorrow. The numerous investigations conducted all-over-the-world have shown that the bottleneck in the energy performances of a caloric cooler is made up by the amplitude of the caloric effect exhibited by the employed solid-state refrigerant. Therefore, since the choice of the most appropriate refrigerant constitutes a critical factor in the energy performances of a cooler, scientific community has increasingly turned its attention upon the development of promising materials for caloric refrigeration, depending on the working temperature range. In this work, we try to delineate a general framework about the energy performances of the caloric materials employable as a refrigerant in room temperature range. The results were carried out by an already experimentally validated model of an active caloric refrigerator.
DOI: 10.18462/iir.thermag.2018.0037
title: Integrated design of active magnetic regenerators and heat exchangers for magnetic refrigerators.

description: Refrigeration systems, including the magnetic ones, require heat exchangers for their operation. Curiously, most of research studies in magnetic cooling do not consider these components in their analyses. This work presents an evaluation of the influence of the heat exchangers on the thermodynamic performance of an active magnetic regenerator. A model based on the ε-NTU method is proposed to integrate the heat exchangers and the regenerator. Commercially available fan assisted tube-fin heat exchangers were selected for the evaluation of the most suitable options for application in a compact magnetic refrigerator. Numerical simulation showed that the influence of the heat exchanger on the regenerator performance can be represented by the product of the heat exchanger effectiveness and the ratio of the thermal capacity rates of the streams. For a system temperature span of 20 K, the best heat exchanger/fan assembly resulted in a reduction of 36.1% in the cooling capacity and an increase of 48.3% in the active magnetic regenerator temperature span.
DOI: 10.5517/ccdc.csd.cc2136s5
title: CCDC 1879926: Experimental Crystal Structure Determination

description: Related Article: M.S. Grigoriev, N.N. Krot|2018|CSD Communication|||
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.7910/dvn/qi2t9a/0i1jvm
title: 20181119-icews-events.zip
DOI: 10.18462/iir.thermag.2018.0003
title: Powder, process parameters and heat treatment conditions for Laser Beam Melting of LaFeSi-based alloys.

description: Shaping magnetocaloric alloys to thin-walled heat exchangers is a viable way to enhance the efficiency of magnetic cooling systems. In this study shaping of La(FeSi)13-based alloys is carried out by Laser Beam Melting (LBM), an Additive Manufacturing method which offers a high degree of geometrical flexibility. Hence this process could be used for a broad variation and optimization of the heat exchanger structures as well as for a small scale production for prototype systems. However, the adaption of the LBM process to La(FeSi)13-alloys requires careful choice of the base powder, the laser melting parameters and the conditions of the subsequent heat treatment. In this work, structures with wall thickness below 500 μm are successfully produced from both La(FeSiCo)13 and LaCe(FeMnSi)13, and the effect of the particle size and composition of the powder and the laser melting parameters is investigated. Additionally, the magnetocaloric entropy change after the heat treatment is reported.
DOI: 10.18462/iir.thermag.2018.0026
title: Investigation of magnetic and structural properties of the FeRh1-xPtx (x = 0.5 -1).

description: In this work, we theoretically investigated the structural and magnetic properties in a series of compositions FeRh1-xPtx (x = 0.5, 0.625, 0.75, 0.875, 1). It is shown that the equilibrium lattice parameter and the type of magnetic ordering change with increasing Pt concentration. For all compositions studied a tetragonal phase is more energetically favorable as compared with a cubic one. For Pt content of х = 0.5 – 0.875, the antiferromagnetic order was found to be stable while in a case of FePt, the ferromagnetic state is preferred. In general, these theoretical results are found in a good agreement with available experimental data.
DOI: 10.18462/iir.thermag.2018.0027
title: Investigation of single wire elastocaloric air cooling potential.

description: The following contribution provides analyses of the air cooling potential of elastocaloric shape memory alloys (SMAs) in form of NiTiCo wires. An essential step consists in developing a scientific test setup, which offers the ability to determine the air-cooling potential under varying conditions like wire geometry, material composition, and process parameters.

With the help of this test setup the influence of different airflow rates on the heat transfer from SMA wire to air and the coherent heat transfer coefficients as well as the expectable air temperature ΔT values are determined and presented in this contribution. Analysing these parameters will greatly support the simulation, development and construction of elastocaloric air cooling devices to provide environmentally friendly alternatives to the prevalent vapour compression based cooling principles.
DOI: 10.18462/iir.thermag.2018.0030
title: Theoretical prediction of the giant magnetocaloric effect in Ni40Co10Mn40Sn7Al3 Heusler alloy.

description: By using ab initio calculations and Monte Carlo simulations, the influence of the small amount of Al on magnetic and magnetocaloric properties of Ni-Co-Mn-Sn Heusler alloy is studied. First-principles calculations have shown that addition of Al leads to an increase in the energy difference between ferromagnetically (FM) ordered austenite and ferrimagnetically (FIM) ordered martensite. The observed tendency points to an increase in the martensitic transformation temperature (Tm) in accordance with the relation ΔE ~ kBTm. The calculated exchange coupling constants, especially for martensite, exhibit the longrange oscillation behavior showing the strong competition between ferromagnetic and antiferromagnetic interactions. By the help of the Hamiltonian model (Potts-Blume-Emery-Griffiths), the temperature dependences of the magnetization, tetragonal deformation, and adiabatic temperature changes for magnetic field variation are obtained. It is shown that the addition of few percent of Al into Ni-Co-Mn-Al leads to increase of the inverse magnetocaloric effect.
DOI: 10.18462/iir.thermag.2018.0033
title: Double perovskites for room temperature magnetocaloric tasks.

description: In previous studies, we have reported that double perovskite La2NiMnO6 (LNMO) presents a nonnegligible potential for room temperature magnetocaloric tasks. With the aim of improving even further the cooling performance and the working temperature range of double perovskites, we report preliminary results on the magnetic and magnetocaloric properties of La2MnFeO6 and related compounds. The substitution onto the lanthanum site enables us to cover a wide operating temperature range extending beyond 300 K. For some optimal growth conditions, the entropy change varies slowly over an unusually large temperature range, which is of clear interest from a practical point of view.
DOI: 10.18462/iir.thermag.2018.0040
title: Continuously operating elastocaloric cooling device based on shape memory alloys: modeling.

description: Elastocaloric cooling based on NiTi exhibits an excellent cooling capability, due to the high specific latent heats activated by mechanical loading/unloading and the small required work input.

The work of the current funding period in the DFG Priority Program SPP 1599, is focused on the development and realization of a continuous operating elastocaloric cooling device. This paper presents the development of an efficient simulation tool for predicting the operation behavior of the system to support the building process of the machine. The model describes the mechanical and thermal characteristics, to find the optimized parameter set for a high-efficient, high-performance cooling unit with a large temperature span while using a minimal amount of SMA material.

The simulation tool and animated visualization tool combines a parallel computing thermo-mechanical SMA model for multiple elastocaloric SMA elements with a mechanical loading system and heat transfer to the heat transport medium to guide the economic development of an efficient cooling device.
DOI: 10.18462/iir.thermag.2018.0042
title: Simulation of a hybrid magnetocaloric-thermoelectric refrigerator.

description: A numerical simulation of a single element of a refrigeration system formed by a sandwich of a magnetocaloric (MC) material between two thermoelectric (TE) cells connecting the cold source to a hot sink is made. The TE cells can be used as thermal diodes or as active elements, while the MC material plays the role of an “elevator” reducing the temperature difference at which the TE cells must work. A simple model for the behaviour of a ferromagnet is deduced to allow fast calculations with many different sets of parameters. Results show that the system can be either very efficient or powerful, depending on the currents through the TE cells.
DOI: 10.18462/iir.thermag.2018.0043
title: Curie temperature effect on the inverse MCE in Ni2MnIn based Heusler alloys near room temperature.

description: We investigate the magneto caloric properties in Ni2MnIn based Heusler alloys having the martensitic to austenitic transition temperatures close to the Curie temperature of the austenitic phase. We tuned the structural transition by composition in order to encounter three possible cases as a function of the increasing temperature: i) the martensite to austenite transition completes before the drop of magnetization associated to the Curie temperature of the austenite, ii) the martensite to austenite transition evolves across the Curie temperature of the austenite and iii) the martensite to austenite transition lies almost completely above the Curie transition of the austenite. When the martensitic transition temperature overlaps with the Curie temperature of the austenite we observe, at constant temperature, the coexistence of direct and inverse magneto caloric effects. In order to understand this behaviour we design a layered structure composed by a 1st order inverse MC material and a 2nd order direct MC material. In this structure, part of the heat exchanged by the direct MCE cooperates with the magnetic field to drive the structural transition further.
DOI: 10.18462/iir.thermag.2018.0001
title: Simulation of a magnetocaloric heating network.

description: The concept and methodology of a magnetocaloric heating network is proposed. A small thermal network consisting of several magnetocaloric heat pumps (MCHP) is considered from the point of their scaling and connection properties. We found a linear scaling law following the heating power variation with AMR mass, which can be included in an MCHP lookup table produced by a 1D transient AMR model. To estimate the performance of networks with different number of MCHPs, a set of single MCHPs coupled through temperature boundary conditions are modelled and network formulas are applied for the reference case of Gd packed beds. A performance optimum is found for specific design points compliant with building heating applications.
DOI: 10.18462/iir.thermag.2018.0002
title: Active magnetic regenerators implemented as a magnetocaloric heat pump for residential buildings.

description: The main objective of the ENOVHEAT project is to develop, build and test the prototype of an innovative and efficient heat pump system based on the active magnetic regenerator technology and to demonstrate that it can be used for building space heating applications. With a maximum COP of 3.93 and a nominal useful heating power output of 2600 W, the ENOVHEAT Gadolinium magnetocaloric heat pump can be integrated into a low-energy house with a vertical borehole ground source heat exchanger and a radiant under-floor heating system within a single hydronic loop. It is able to provide for the dwelling’s space heating needs under Danish winter conditions. Moreover, a control strategy for heat energy storage in the indoor environment can be employed to optimize the MCHP operation and reach seasonal COPs of up to 3.51. However, the layered La(Fe,Mn,Si)13Hy prototype is currently not suitable for such application.
DOI: 10.18462/iir.thermag.2018.0004
title: Fast synthesis and magnetocaloric properties of La(Fe, Co, Si)13 compounds and their hydrides.

description: LaFe11.5-xCoxSi1.5 alloys (0 ≤ x ≤ 2.2) have been synthetized using high energy ball milling and one of either short annealing treatment or reactive Spark Plasma Sintering. Corresponding hydrides were prepared using a Sievert method. The alloys were characterized by XRD and EPMA and the hydrides by XRD. The physical properties of all compounds were determined using magnetic measurements, DSC and Mössbauer spectroscopy. A significant increase of their cell volume is observed between paramagnetic towards ferromagnetic state. By increasing the Co content a continuous increase of the TC and the mean hyperfine field BHF has been observed. The study of corresponding hydrides shows that TC increase is not a pure additional effect but some electronic interactions between Co and H should be taken into account. Their magnetocaloric properties are a combination of both the influence of Co substitution and hydrogen insertion.
DOI: 10.18462/iir.thermag.2018.0007
title: Numerical simulations and experimental tests of Gd-Y multi-layered active magnetic regenerators.

description: Magnetic cooling still needs to overcome some challenges to become a commercially competitive technology. One of these challenges is to make the best use of the magnetocaloric effect of the material in the active magnetic regenerator (AMR). In this work, we have evaluated through 1-D numerical simulations different parameters that may be used to optimize a multi-layered AMR composed of second-order Gd-Y alloys. We have characterized their thermo-physical properties, such as heat capacity, magnetization, magnetic entropy change and adiabatic temperature change as a function of temperature and magnetic field. The AMR parameters, such as number of layers and layer length fraction, were varied in order to maximize the cooling capacity for a fixed temperature span. An experimental validation of the numerical simulations was carried out in an AMR test apparatus using a regenerator bed composed by two and three layers of Gd-Y spheres with different Curie temperatures.
DOI: 10.18462/iir.thermag.2018.0015
title: Freeze-casting to create directional micro-channels in regenerators for magnetic refrigeration.

description: We present the engineering of directional porosity in the form of lamellar micro-channels in the magnetocaloric ceramic of La0.66Ca0.27Sr0.06Mn1.05O3 (LCSM) by freeze-casting. Freeze-casting is a templating technique based on the anisotropic growth of ice crystals in aqueous suspensions upon directional freezing, which, when applied to a suspension of LCSM results in hierarchical structures of aligned porosity in the form of micro-channels with widths of 5 μm to 20 μm. Channel sizes and tortuosity are measured and calculated from analysis of SEM images obtained at cross sections perpendicular and parallel to the freezing direction, respectively, while freezing conditions are monitored by temperature measurements. We propose that freeze-casting demonstrate apparent applicability within processing of ceramic materials for application as regenerator for magnetic refrigeration.