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International journal of refrigeration |
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Ajouter le résultat dans votre panierFrom conventional to magnetic refrigerator technology / Osmann Sari in International journal of refrigeration, Vol. 37 N° 1 (Janvier 2014)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 8–15
Titre : From conventional to magnetic refrigerator technology Titre original : Du froid conventionnel au froid magnétique Type de document : texte imprimé Auteurs : Osmann Sari, Auteur ; Mohamed Balli, Auteur Année de publication : 2014 Article en page(s) : pp. 8–15 Note générale : refrigeration Langues : Anglais (eng) Mots-clés : Conventional refrigeration; refrigerants; magnetic refrigeration; magnetocaloric material; magnetic field sources Résumé : Ensure wellbeing for each of us is a first necessity for peace and development of society while preserving the environmental balance of the blue planet. Today's society is faced with major challenges such as the supply of energy, water, food, etc. Refrigeration is an important factor in the modern world. It is vital before life (sperm banks), for life (conversation food, medicine, …), and after life (preservation of human organs and tissues). However the negative impact of refrigeration on the environment is visible and, consequently, refrigeration systems are subject to prescriptive regulation. This regulation provides a great opportunity for the emergence of new refrigeration technologies and new product markets. In recent years, magnetic refrigeration is considered as a serious alternative for conventional systems. Today proof of the concept is established. Therefore what remains is to provide systems for the society. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002612 [article] From conventional to magnetic refrigerator technology = Du froid conventionnel au froid magnétique [texte imprimé] / Osmann Sari, Auteur ; Mohamed Balli, Auteur . - 2014 . - pp. 8–15.
refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 8–15
Mots-clés : Conventional refrigeration; refrigerants; magnetic refrigeration; magnetocaloric material; magnetic field sources Résumé : Ensure wellbeing for each of us is a first necessity for peace and development of society while preserving the environmental balance of the blue planet. Today's society is faced with major challenges such as the supply of energy, water, food, etc. Refrigeration is an important factor in the modern world. It is vital before life (sperm banks), for life (conversation food, medicine, …), and after life (preservation of human organs and tissues). However the negative impact of refrigeration on the environment is visible and, consequently, refrigeration systems are subject to prescriptive regulation. This regulation provides a great opportunity for the emergence of new refrigeration technologies and new product markets. In recent years, magnetic refrigeration is considered as a serious alternative for conventional systems. Today proof of the concept is established. Therefore what remains is to provide systems for the society. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002612
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 16-27
Titre : Electrocaloric vs. magnetocaloric energy conversion Titre original : Comparaisons des conversions d'énergie électrocalorique et magnétocalorique Type de document : texte imprimé Auteurs : M. Ožbolt, Auteur ; A. Kitanovski, Auteur ; J. Tušek, Auteur Année de publication : 2014 Article en page(s) : pp. 16-27 Note générale : refrigeration Langues : Anglais (eng) Mots-clés : Electrocaloric effect; magnetocaloric effect; magnetic refrigeration; energy conversion; refrigeration Résumé : Currently, one of the most interesting alternatives to conventional compressor refrigeration is magnetic refrigeration. However, despite its great potential, some important obstacles, relating mostly to the relatively low power density and the related high costs, must be overcome. Another alternative, which also shows great potential, is electrocaloric refrigeration. Until recently, electrocaloric materials were not so common; however, a number of different electrocaloric materials exist today. Like magnetocalorics, these can be used in the form of a regenerator in order to increase the temperature span. Based on a previously developed numerical model, we have made a comparison between electrocaloric and magnetocaloric regenerators. The results suggest that electrocaloric energy conversion represents a serious alternative, not only to compressor-based technologies, but also to magnetocalorics. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001655 [article] Electrocaloric vs. magnetocaloric energy conversion = Comparaisons des conversions d'énergie électrocalorique et magnétocalorique [texte imprimé] / M. Ožbolt, Auteur ; A. Kitanovski, Auteur ; J. Tušek, Auteur . - 2014 . - pp. 16-27.
refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 16-27
Mots-clés : Electrocaloric effect; magnetocaloric effect; magnetic refrigeration; energy conversion; refrigeration Résumé : Currently, one of the most interesting alternatives to conventional compressor refrigeration is magnetic refrigeration. However, despite its great potential, some important obstacles, relating mostly to the relatively low power density and the related high costs, must be overcome. Another alternative, which also shows great potential, is electrocaloric refrigeration. Until recently, electrocaloric materials were not so common; however, a number of different electrocaloric materials exist today. Like magnetocalorics, these can be used in the form of a regenerator in order to increase the temperature span. Based on a previously developed numerical model, we have made a comparison between electrocaloric and magnetocaloric regenerators. The results suggest that electrocaloric energy conversion represents a serious alternative, not only to compressor-based technologies, but also to magnetocalorics. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001655
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 28-35
Titre : New thermodynamic cycles for magnetic refrigeration Titre original : Nouveaux cycles thermodynamiques pour le froid magnétique Type de document : texte imprimé Auteurs : A. Kitanovski, Auteur ; U. Plaznik, Auteur ; J. Tušek, Auteur Année de publication : 2014 Article en page(s) : pp. 28-35 Note générale : refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; active magnetic regenerator; thermodynamic cycle; energy efficiency; heat transfe Résumé : Most of the existing prototype devices for magnetic refrigeration are based on a thermodynamic cycle with an active magnetic regenerator (AMR) that operates as a Brayton-type regenerative magnetic refrigeration cycle. However, there are several other cycles that may potentially influence not only the efficiency, but also the cost, compactness and simplicity of magnetocaloric devices. In this article we discuss the possibility of introducing new thermodynamic cycles. This is supported by information about, and a comparison of, the corresponding magnetic field sources. We present the results of numerical analyses and compare the characteristics of different thermodynamic cycles under different operating conditions and for different magnetic field intensities. Guidelines for future work on new magnetic thermodynamic cycles are presented. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001412 [article] New thermodynamic cycles for magnetic refrigeration = Nouveaux cycles thermodynamiques pour le froid magnétique [texte imprimé] / A. Kitanovski, Auteur ; U. Plaznik, Auteur ; J. Tušek, Auteur . - 2014 . - pp. 28-35.
refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 28-35
Mots-clés : Magnetic refrigeration; active magnetic regenerator; thermodynamic cycle; energy efficiency; heat transfe Résumé : Most of the existing prototype devices for magnetic refrigeration are based on a thermodynamic cycle with an active magnetic regenerator (AMR) that operates as a Brayton-type regenerative magnetic refrigeration cycle. However, there are several other cycles that may potentially influence not only the efficiency, but also the cost, compactness and simplicity of magnetocaloric devices. In this article we discuss the possibility of introducing new thermodynamic cycles. This is supported by information about, and a comparison of, the corresponding magnetic field sources. We present the results of numerical analyses and compare the characteristics of different thermodynamic cycles under different operating conditions and for different magnetic field intensities. Guidelines for future work on new magnetic thermodynamic cycles are presented. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001412
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 36-42
Titre : Thermal investigations of an experimental active magnetic regenerative refrigerator operating near room temperature Titre original : Etudes thermiques d'un réfrigérateur magnétique actif expérimental fonctionnant à température ambiante Type de document : texte imprimé Auteurs : Y. Chiba, Auteur ; Smaili, Arezki, Auteur ; C. Mahmed, Auteur Année de publication : 2014 Article en page(s) : pp. 36-42 Note générale : refrigeration Langues : Anglais (eng) Mots-clés : Active magnetic regenerator; numerical simulation; magnetocaloric effect; thermal analysis Résumé : In this paper, numerical and experimental investigations on a magnetic refrigeration device based upon the active magnetic regeneration (AMR) cycle operating near room temperature are presented. A numerical 1D model based on the transient energy equations is proposed for modelling the heat exchange between the magnetocaloric material and the carrier fluid in the regenerator bed. The validity of 1D AMR-numerical model is investigated through the recently developed magnetic cooling demonstrator by Clean Cooling Systems SA (CCS) at the University of Applied Sciences of western Switzerland (HES−SO). The obtained results including the temperature span, the coefficient of performance and the cooling power are presented and discussed. In general, good agreements have been noted between the experimental and numerical results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002727 [article] Thermal investigations of an experimental active magnetic regenerative refrigerator operating near room temperature = Etudes thermiques d'un réfrigérateur magnétique actif expérimental fonctionnant à température ambiante [texte imprimé] / Y. Chiba, Auteur ; Smaili, Arezki, Auteur ; C. Mahmed, Auteur . - 2014 . - pp. 36-42.
refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 36-42
Mots-clés : Active magnetic regenerator; numerical simulation; magnetocaloric effect; thermal analysis Résumé : In this paper, numerical and experimental investigations on a magnetic refrigeration device based upon the active magnetic regeneration (AMR) cycle operating near room temperature are presented. A numerical 1D model based on the transient energy equations is proposed for modelling the heat exchange between the magnetocaloric material and the carrier fluid in the regenerator bed. The validity of 1D AMR-numerical model is investigated through the recently developed magnetic cooling demonstrator by Clean Cooling Systems SA (CCS) at the University of Applied Sciences of western Switzerland (HES−SO). The obtained results including the temperature span, the coefficient of performance and the cooling power are presented and discussed. In general, good agreements have been noted between the experimental and numerical results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002727
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 43-50
Titre : 1D model of an active magnetic regenerator Titre original : Modèle unidimensionnel d'un régénérateur actif magnétique Type de document : texte imprimé Auteurs : P. Nikkola, Auteur ; C. Mahmed, Auteur ; M. Balli, Auteur Année de publication : 2014 Article en page(s) : pp. 43-50 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; magnetic cooling; AMR; modeling; finite differences Résumé : The 1D active magnetic regenerator model developed at the University of Applied Sciences of Western Switzerland is described. The system of two partial differential equations is discretized with the finite differences method backward in time and solved with the tridiagonal matrix algorithm. New features, not found in the literature in 1D models, are thermal losses in the regenerator, parasitic heat exchange, and the calculation of the AMR cycle output power in steady state. The model is implemented in MATLAB and it has a graphical user interface. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002600 [article] 1D model of an active magnetic regenerator = Modèle unidimensionnel d'un régénérateur actif magnétique [texte imprimé] / P. Nikkola, Auteur ; C. Mahmed, Auteur ; M. Balli, Auteur . - 2014 . - pp. 43-50.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 43-50
Mots-clés : Magnetic refrigeration; magnetic cooling; AMR; modeling; finite differences Résumé : The 1D active magnetic regenerator model developed at the University of Applied Sciences of Western Switzerland is described. The system of two partial differential equations is discretized with the finite differences method backward in time and solved with the tridiagonal matrix algorithm. New features, not found in the literature in 1D models, are thermal losses in the regenerator, parasitic heat exchange, and the calculation of the AMR cycle output power in steady state. The model is implemented in MATLAB and it has a graphical user interface. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002600
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 51-62
Titre : Performance modeling of AMR refrigerators Titre original : Modélisation de la performance de réfrigérateurs à régénérateurs magnétiques actifs Type de document : texte imprimé Auteurs : Thomas Burdyny, Auteur ; Alex Ruebsaat-Trott, Auteur ; Andrew Rowe, Auteur Année de publication : 2014 Article en page(s) : pp. 51-62 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : AMR cycle; thermodynamics; magnetocaloric effect; magnetic refrigeration Résumé : A system modeling approach for predicting the performance of active magnetic regenerators using a one-phase approximation is presented. The approach is described for an arbitrary AMR device independent of the magnetic refrigerant, thermal losses or magnetic waveform. A general expression for magnetic work is derived which can be used for cycles where the low-field intensity is not zero. Additionally, a means of treating the varying magnetic field waveform as a single high and low field is described. The model is applied to a permanent magnet magnetic refrigerator using water–glycol as the heat transfer fluid. Simulated results are compared to experimental data which vary by heat load, frequency and utilization. A sensitivity analysis is performed using utilization, adiabatic temperature change, effective conductivity and particle size as independent variables. Comparisons to experimental data show that reducing the calculated magnetocaloric effect by 25% provides good agreement between simulations and experimental results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002119 [article] Performance modeling of AMR refrigerators = Modélisation de la performance de réfrigérateurs à régénérateurs magnétiques actifs [texte imprimé] / Thomas Burdyny, Auteur ; Alex Ruebsaat-Trott, Auteur ; Andrew Rowe, Auteur . - 2014 . - pp. 51-62.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 51-62
Mots-clés : AMR cycle; thermodynamics; magnetocaloric effect; magnetic refrigeration Résumé : A system modeling approach for predicting the performance of active magnetic regenerators using a one-phase approximation is presented. The approach is described for an arbitrary AMR device independent of the magnetic refrigerant, thermal losses or magnetic waveform. A general expression for magnetic work is derived which can be used for cycles where the low-field intensity is not zero. Additionally, a means of treating the varying magnetic field waveform as a single high and low field is described. The model is applied to a permanent magnet magnetic refrigerator using water–glycol as the heat transfer fluid. Simulated results are compared to experimental data which vary by heat load, frequency and utilization. A sensitivity analysis is performed using utilization, adiabatic temperature change, effective conductivity and particle size as independent variables. Comparisons to experimental data show that reducing the calculated magnetocaloric effect by 25% provides good agreement between simulations and experimental results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002119
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 72–77
Titre : A test stand to study the possibility of using magnetocaloric materials for refrigerators Titre original : Un banc d'essai pour étudier la possibilité d'utiliser des matériaux magnétocaloriques dans les réfrigérateurs Type de document : texte imprimé Auteurs : A. Czernuszewicz, Auteur ; J. Kaleta, Auteur ; M. Królewicz, Auteur Année de publication : 2014 Article en page(s) : pp. 72–77 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; magnetic refrigeration; magnetic cooling; gadolinium Résumé : A laboratory test stand for magnetocaloric effect investigations has been developed. The test stand is compact and easily reconfigurable. Gadolinium in the form of particles is used as a refrigerant. The material is magnetized/demagnetized due to the reciprocating motion of a magnetic bed. A Halbach array of permanent magnets is employed as a magnetic field source. It generates a magnetic field of about 1 T. In order to decrease the distance along which the magnetic bed has to move, a magnetic shield was used which limits the range of external magnetic field influence. The effectiveness of the shielding and the decrease in magnetic field intensity were shown in the form of magnetic field distribution maps. The paper presents first experimental results which are measured as the temperature difference between the two outermost reservoirs. The achieved results are promising – the temperature span between the heat exchangers amounts to about 2 °C. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300251X [article] A test stand to study the possibility of using magnetocaloric materials for refrigerators = Un banc d'essai pour étudier la possibilité d'utiliser des matériaux magnétocaloriques dans les réfrigérateurs [texte imprimé] / A. Czernuszewicz, Auteur ; J. Kaleta, Auteur ; M. Królewicz, Auteur . - 2014 . - pp. 72–77.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 72–77
Mots-clés : Magnetocaloric effect; magnetic refrigeration; magnetic cooling; gadolinium Résumé : A laboratory test stand for magnetocaloric effect investigations has been developed. The test stand is compact and easily reconfigurable. Gadolinium in the form of particles is used as a refrigerant. The material is magnetized/demagnetized due to the reciprocating motion of a magnetic bed. A Halbach array of permanent magnets is employed as a magnetic field source. It generates a magnetic field of about 1 T. In order to decrease the distance along which the magnetic bed has to move, a magnetic shield was used which limits the range of external magnetic field influence. The effectiveness of the shielding and the decrease in magnetic field intensity were shown in the form of magnetic field distribution maps. The paper presents first experimental results which are measured as the temperature difference between the two outermost reservoirs. The achieved results are promising – the temperature span between the heat exchangers amounts to about 2 °C. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300251X
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 63-71
Titre : Multiobjective optimization of AMR systems Titre original : Optimisation multi-objectifs de systèmes de froid magnétique actif Type de document : texte imprimé Auteurs : H. R. E. H. Bouchekara, Auteur ; A. Kedous-Lebouc, Auteur ; J.-P. Yonnet, Auteur Année de publication : 2014 Article en page(s) : pp. 63-71 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : AMR; optimal design; magnetic refrigerator; multiobjective optimization Résumé : In this paper, computational algorithms of different multiobjective optimization techniques and their application for AMR systems are presented. In order to illustrate the effectiveness of the proposed methods, they have been demonstrated on a layered AMR bed, where four objective functions are considered, namely: the temperature span, the cooling energy, the number of cycles to reach steady state and the masse of the MCM. The weighted sum, weighted product, Keeney-Raiffa, distance to a reference goal and ε-constraint methods are described along with a comparative study of the results. The results from the multiobjective optimization methods are evaluated in terms of the supercriterion S and the Euclidean distance N. It is concluded that the results obtained using some methods, like the weighting methods, are properly balanced yielding the best compromise in the presence of conflicting objectives while some other methods, like the distance to a reference goal method and the ε-constraint method, allow to reach predefined goals or to respect additional constraints. Moreover, methods like distance to a reference one or the ε-constraint one need some expertise and insights. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002430 [article] Multiobjective optimization of AMR systems = Optimisation multi-objectifs de systèmes de froid magnétique actif [texte imprimé] / H. R. E. H. Bouchekara, Auteur ; A. Kedous-Lebouc, Auteur ; J.-P. Yonnet, Auteur . - 2014 . - pp. 63-71.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 63-71
Mots-clés : AMR; optimal design; magnetic refrigerator; multiobjective optimization Résumé : In this paper, computational algorithms of different multiobjective optimization techniques and their application for AMR systems are presented. In order to illustrate the effectiveness of the proposed methods, they have been demonstrated on a layered AMR bed, where four objective functions are considered, namely: the temperature span, the cooling energy, the number of cycles to reach steady state and the masse of the MCM. The weighted sum, weighted product, Keeney-Raiffa, distance to a reference goal and ε-constraint methods are described along with a comparative study of the results. The results from the multiobjective optimization methods are evaluated in terms of the supercriterion S and the Euclidean distance N. It is concluded that the results obtained using some methods, like the weighting methods, are properly balanced yielding the best compromise in the presence of conflicting objectives while some other methods, like the distance to a reference goal method and the ε-constraint method, allow to reach predefined goals or to respect additional constraints. Moreover, methods like distance to a reference one or the ε-constraint one need some expertise and insights. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002430
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 78-83
Titre : Development and experimental results from a 1 kW prototype AMR Titre original : Développement d'un prototype de régénérateur magnétique actif d'une puissance de 1 kW et résultats expérimentaux Type de document : texte imprimé Auteurs : C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur ; D. Eriksen, Auteur Année de publication : 2014 Article en page(s) : pp. 78-83 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; magnetocaloric device; active magnetic regenerator; gadolinium Résumé : A novel rotary magnetic refrigeration device has been designed and constructed following the concepts recently outlined in Bahl et al. (2011). The magnet and flow system design allow for almost continuous usage of both the magnetic field and the magnetocaloric material in 24 cassettes, each containing an active magnetic regenerator (AMR) bed. The prototype design facilitates easy exchange of the 24 cassettes, allowing the testing of different material amounts and compositions. Operating with 2.8 kg of commercial grade Gd spheres a maximum no-span cooling power of 1010 W and a maximum zero load temperature span of 25.4 K have been achieved. For the purpose of actual operation, simultaneous high span and high performance is required. At a heat load of 200 W a high temperature span of 18.9 K has been obtained, dropping to a span of 13.8 K at the higher heat load value of 400 W. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300234X [article] Development and experimental results from a 1 kW prototype AMR = Développement d'un prototype de régénérateur magnétique actif d'une puissance de 1 kW et résultats expérimentaux [texte imprimé] / C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur ; D. Eriksen, Auteur . - 2014 . - pp. 78-83.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 78-83
Mots-clés : Magnetic refrigeration; magnetocaloric device; active magnetic regenerator; gadolinium Résumé : A novel rotary magnetic refrigeration device has been designed and constructed following the concepts recently outlined in Bahl et al. (2011). The magnet and flow system design allow for almost continuous usage of both the magnetic field and the magnetocaloric material in 24 cassettes, each containing an active magnetic regenerator (AMR) bed. The prototype design facilitates easy exchange of the 24 cassettes, allowing the testing of different material amounts and compositions. Operating with 2.8 kg of commercial grade Gd spheres a maximum no-span cooling power of 1010 W and a maximum zero load temperature span of 25.4 K have been achieved. For the purpose of actual operation, simultaneous high span and high performance is required. At a heat load of 200 W a high temperature span of 18.9 K has been obtained, dropping to a span of 13.8 K at the higher heat load value of 400 W. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300234X
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 84-91
Titre : The performance of a large-scale rotary magnetic refrigerator Titre original : Performance d'un réfrigérateur magnétique rotatif de grande échelle Type de document : texte imprimé Auteurs : S. Jacobs, Auteur ; J. Auringer, Auteur ; A. Boeder, Auteur Année de publication : 2014 Article en page(s) : pp. 84-91 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; magnetocaloric material; active magnetic regeneration; COP Résumé : Astronautics has constructed a large-scale rotary magnetic refrigerator which was designed to provide 2 kW of cooling power over a temperature span of 12 K with Electrical Coefficient Of Performance (COPe) > 2. The system uses a NdFeB magnet assembly with peak field of 1.44 T which rotates over twelve beds arranged circumferentially. Each bed was packed with six layers of LaFeSiH of different Curie temperatures, chosen to optimize system performance over the desired span. We report here on the performance of this system at flow rates ranging from 12.5 to 21.2 L min−1. At the largest flow rate, the system produced 3042 W of cooling power at zero span and peak performance of 2502 W over a span of 11 K. To our knowledge, this represents the largest cooling power yet observed for a magnetic refrigeration system. We show that the measured performance is in good agreement with theoretical prediction. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002594 [article] The performance of a large-scale rotary magnetic refrigerator = Performance d'un réfrigérateur magnétique rotatif de grande échelle [texte imprimé] / S. Jacobs, Auteur ; J. Auringer, Auteur ; A. Boeder, Auteur . - 2014 . - pp. 84-91.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 84-91
Mots-clés : Magnetic refrigeration; magnetocaloric material; active magnetic regeneration; COP Résumé : Astronautics has constructed a large-scale rotary magnetic refrigerator which was designed to provide 2 kW of cooling power over a temperature span of 12 K with Electrical Coefficient Of Performance (COPe) > 2. The system uses a NdFeB magnet assembly with peak field of 1.44 T which rotates over twelve beds arranged circumferentially. Each bed was packed with six layers of LaFeSiH of different Curie temperatures, chosen to optimize system performance over the desired span. We report here on the performance of this system at flow rates ranging from 12.5 to 21.2 L min−1. At the largest flow rate, the system produced 3042 W of cooling power at zero span and peak performance of 2502 W over a span of 11 K. To our knowledge, this represents the largest cooling power yet observed for a magnetic refrigeration system. We show that the measured performance is in good agreement with theoretical prediction. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002594
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 92–98
Titre : Experimental and numerical results of a high frequency rotating active magnetic refrigerator Titre original : Réfrigérateur magnétique actif rotatif à haute fréquence: résultats expérimentaux et numériques Type de document : texte imprimé Auteurs : J. A. Lozano, Auteur ; K. Engelbrecht, Auteur ; C. R. H. Bahl, Auteur Année de publication : 2014 Article en page(s) : pp. 92–98 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Active magnetic regenerator; magnetic refrigeration; experiment; numerical modelling; parasitic losses analysis Résumé : Experimental results for a recently developed prototype magnetic refrigeration device at the Technical University of Denmark (DTU) were obtained and compared with numerical simulation results. A continuously rotating active magnetic regenerator (AMR) using 2.8 kg packed sphere regenerators of gadolinium (Gd) was employed. With operating frequencies up to 10 Hz and volumetric flow rates up to 600 L h−1, the prototype has shown high performance and the results are consistent with predictions from numerical modelling. Magnetocaloric properties of the Gd spheres were obtained experimentally and implemented in a one-dimensional numerical AMR model that includes also the parasitic losses from the prototype. The temperature span for a thermal load of 200 W as a function of frequency was measured and modelled. Moreover, the temperature span dependence on the cooling capacity as a function of cycle frequency was determined. A detailed study of these parasitic losses was carried out experimentally and numerically. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002351 [article] Experimental and numerical results of a high frequency rotating active magnetic refrigerator = Réfrigérateur magnétique actif rotatif à haute fréquence: résultats expérimentaux et numériques [texte imprimé] / J. A. Lozano, Auteur ; K. Engelbrecht, Auteur ; C. R. H. Bahl, Auteur . - 2014 . - pp. 92–98.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 92–98
Mots-clés : Active magnetic regenerator; magnetic refrigeration; experiment; numerical modelling; parasitic losses analysis Résumé : Experimental results for a recently developed prototype magnetic refrigeration device at the Technical University of Denmark (DTU) were obtained and compared with numerical simulation results. A continuously rotating active magnetic regenerator (AMR) using 2.8 kg packed sphere regenerators of gadolinium (Gd) was employed. With operating frequencies up to 10 Hz and volumetric flow rates up to 600 L h−1, the prototype has shown high performance and the results are consistent with predictions from numerical modelling. Magnetocaloric properties of the Gd spheres were obtained experimentally and implemented in a one-dimensional numerical AMR model that includes also the parasitic losses from the prototype. The temperature span for a thermal load of 200 W as a function of frequency was measured and modelled. Moreover, the temperature span dependence on the cooling capacity as a function of cycle frequency was determined. A detailed study of these parasitic losses was carried out experimentally and numerically. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002351
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 99-105
Titre : Design improvements of a permanent magnet active magnetic refrigerator Titre original : Amélioration de la conception d'un réfrigérateur magnétique actif permanent Type de document : texte imprimé Auteurs : D.S. Arnold, Auteur ; A. Tura, Auteur ; Alex Ruebsaat-Trott, Auteur Année de publication : 2014 Article en page(s) : pp. 99-105 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Permanent magnet magnetic refrigerator; AMR cycle Résumé : A second-generation room-temperature permanent magnet active magnetic regenerator test apparatus using Halbach arrays is described. The magnet arrays consist of three concentric cylinders. Each cylinder is constructed using 12 permanent magnet segments. The inner magnet array is stationary while the intermediate and outer arrays are designed to rotate in opposite directions so as to create a sinusoidal magnetic field waveform with a stationary field direction. The fluid flow system utilizes a novel check valve configuration so that fluid dead volumes are minimized. The system construction is modular to allow for quick replacement of material or system components. Fringing fields near the outer and inner diameters of the arrays are found to create large forces between arrays leading to large torques. Test results using 650 g of gadolinium spheres produce a no-load temperature span of 33 K at 0.8 Hz. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002582 [article] Design improvements of a permanent magnet active magnetic refrigerator = Amélioration de la conception d'un réfrigérateur magnétique actif permanent [texte imprimé] / D.S. Arnold, Auteur ; A. Tura, Auteur ; Alex Ruebsaat-Trott, Auteur . - 2014 . - pp. 99-105.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 99-105
Mots-clés : Permanent magnet magnetic refrigerator; AMR cycle Résumé : A second-generation room-temperature permanent magnet active magnetic regenerator test apparatus using Halbach arrays is described. The magnet arrays consist of three concentric cylinders. Each cylinder is constructed using 12 permanent magnet segments. The inner magnet array is stationary while the intermediate and outer arrays are designed to rotate in opposite directions so as to create a sinusoidal magnetic field waveform with a stationary field direction. The fluid flow system utilizes a novel check valve configuration so that fluid dead volumes are minimized. The system construction is modular to allow for quick replacement of material or system components. Fringing fields near the outer and inner diameters of the arrays are found to create large forces between arrays leading to large torques. Test results using 650 g of gadolinium spheres produce a no-load temperature span of 33 K at 0.8 Hz. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002582
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 106–116
Titre : Concentric Halbach cylinder magnetic refrigerator cost optimization Titre original : Optimisation du coût d'un réfrigérateur magnétique à deux cylindres d'Halbach Type de document : texte imprimé Auteurs : A. Tura, Auteur ; A. Rowe, Auteur Année de publication : 2014 Article en page(s) : pp. 106–116 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Gadolinium; magnetocaloric effect; active magnetic regenerator; efficiency; magnetic refrigerator; optimization Résumé : Commercial magnetic refrigeration near room temperature faces technological challenges and high costs. Although several laboratory devices have been developed, no design is realistically close to the performance, reliability, and financial proposition of a vapor compression refrigerator.
This study examines the total cost of cooling provided by an idealized dual-regenerator concentric Halbach design. An optimization process, based on a simplified analytical model rather than a computationally intensive finite element model, is applied to geometrical and operational parameters, with the objective function minimizing capital and operating cost. Additionally, the model utilizes a refrigerant with ideal magnetocaloric (MCE) properties and constant specific heat. The model is first validated against extrapolated experimental data from an existing device, and then the optimization routine is applied to a range of cooling demand and MCE values. Results help in identifying target refrigerant properties, and refrigerator geometrical/operational parameters. Moreover, a sensitivity analysis demonstrates how the design variables affect the system performance.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002387 [article] Concentric Halbach cylinder magnetic refrigerator cost optimization = Optimisation du coût d'un réfrigérateur magnétique à deux cylindres d'Halbach [texte imprimé] / A. Tura, Auteur ; A. Rowe, Auteur . - 2014 . - pp. 106–116.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 106–116
Mots-clés : Gadolinium; magnetocaloric effect; active magnetic regenerator; efficiency; magnetic refrigerator; optimization Résumé : Commercial magnetic refrigeration near room temperature faces technological challenges and high costs. Although several laboratory devices have been developed, no design is realistically close to the performance, reliability, and financial proposition of a vapor compression refrigerator.
This study examines the total cost of cooling provided by an idealized dual-regenerator concentric Halbach design. An optimization process, based on a simplified analytical model rather than a computationally intensive finite element model, is applied to geometrical and operational parameters, with the objective function minimizing capital and operating cost. Additionally, the model utilizes a refrigerant with ideal magnetocaloric (MCE) properties and constant specific heat. The model is first validated against extrapolated experimental data from an existing device, and then the optimization routine is applied to a range of cooling demand and MCE values. Results help in identifying target refrigerant properties, and refrigerator geometrical/operational parameters. Moreover, a sensitivity analysis demonstrates how the design variables affect the system performance.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002387
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 117-126
Titre : Experimental comparison of multi-layered La–Fe–Co–Si and single-layered Gd active magnetic regenerators for use in a room-temperature magnetic refrigerator Titre original : Comparaison expérimentale de réfrigérateurs au La-Fe-Co-Si à couches multiples et au Gd à couches simples pour l'utilisation dans un réfrigérateur magnétique à température ambiante Type de document : texte imprimé Auteurs : Jaka Tušek, Auteur ; Andrej Kitanovski, Auteur ; Urban Tomc, Auteur Année de publication : 2014 Article en page(s) : pp. 117-126 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; active magnetic regenerator; magnetocaloric materials; experiments; heat transfer Résumé : We present experimental comparison of different parallel-plate active magnetic regenerators (AMRs) with two different groups of magnetocaloric materials. First, a gadolinium-based single-layered AMR was tested and analysed under different operating conditions. In the next step, three different multi-layered AMRs with different compositions and different Curie temperatures made from LaFe13 − x − yCoxSiy materials were constructed and tested. Seven-, four- and two-layered La-based AMRs were evaluated. The measurements were performed with respect to the maximum measured temperature span under different operating conditions and the cooling load under different temperature spans. In order to find the optimum operating temperature range the AMRs were further compared for different hot-side temperatures. The Gd-based AMR produced a larger temperature span, especially at higher operating frequencies and higher mass-flow rates. Among the multi-layered La–Fe–Co–Si AMRs, the seven- and four-layered AMRs showed very similar characteristics, while the two-layered AMR was much poorer. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002363 [article] Experimental comparison of multi-layered La–Fe–Co–Si and single-layered Gd active magnetic regenerators for use in a room-temperature magnetic refrigerator = Comparaison expérimentale de réfrigérateurs au La-Fe-Co-Si à couches multiples et au Gd à couches simples pour l'utilisation dans un réfrigérateur magnétique à température ambiante [texte imprimé] / Jaka Tušek, Auteur ; Andrej Kitanovski, Auteur ; Urban Tomc, Auteur . - 2014 . - pp. 117-126.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 117-126
Mots-clés : Magnetic refrigeration; active magnetic regenerator; magnetocaloric materials; experiments; heat transfer Résumé : We present experimental comparison of different parallel-plate active magnetic regenerators (AMRs) with two different groups of magnetocaloric materials. First, a gadolinium-based single-layered AMR was tested and analysed under different operating conditions. In the next step, three different multi-layered AMRs with different compositions and different Curie temperatures made from LaFe13 − x − yCoxSiy materials were constructed and tested. Seven-, four- and two-layered La-based AMRs were evaluated. The measurements were performed with respect to the maximum measured temperature span under different operating conditions and the cooling load under different temperature spans. In order to find the optimum operating temperature range the AMRs were further compared for different hot-side temperatures. The Gd-based AMR produced a larger temperature span, especially at higher operating frequencies and higher mass-flow rates. Among the multi-layered La–Fe–Co–Si AMRs, the seven- and four-layered AMRs showed very similar characteristics, while the two-layered AMR was much poorer. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002363
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 127–134
Titre : The influence of non-magnetocaloric properties on the performance in parallel-plate AMRs Titre original : Influence des propriétés non magnétocaloriques sur la performance des plaques parallèles de réfrigérateurs magnétiques actifs Type de document : texte imprimé Auteurs : K.K. Nielsen, Auteur ; C. R. H. Bahl, Auteur ; A. Smith, Auteur Année de publication : 2014 Article en page(s) : pp. 127–134 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Modelling; flow maldistribution; demagnetizing effects; magnetic refrigeration Résumé : The performance of Active Magnetic Regenerators (AMR) does not depend solely on the magnetocaloric effect of their constituents. Rather, it depends on several additional parameters, including, magnetic field, geometry (hydraulic diameter, cross-sectional area, regenerator length etc.), thermal properties (conductivity, specific heat and mass density) and operating parameters (utilization, frequency, number of transfer units etc.). In this paper we focus on the influence of three parameters on regenerator performance: 1) Solid thermal conductivity, 2) magnetostatic demagnetization and 3) flow maldistribution due to geometrically non-uniform regenerators. It is shown that the AMR performance is optimal at an intermediate value of the solid thermal conductivity for many operating conditions. The magnetostatic demagnetization is shown to have a significant influence on the AMR performance, giving a strong dependence on the orientation of the applied field and the regenerator geometry. Finally, the flow maldistribution of non-uniform regenerator geometries is found to degrade the AMR performance even at minor deviations from perfectly homogeneous regenerator matrices. This paper reflects a summary of various recently published results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002569 [article] The influence of non-magnetocaloric properties on the performance in parallel-plate AMRs = Influence des propriétés non magnétocaloriques sur la performance des plaques parallèles de réfrigérateurs magnétiques actifs [texte imprimé] / K.K. Nielsen, Auteur ; C. R. H. Bahl, Auteur ; A. Smith, Auteur . - 2014 . - pp. 127–134.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 127–134
Mots-clés : Modelling; flow maldistribution; demagnetizing effects; magnetic refrigeration Résumé : The performance of Active Magnetic Regenerators (AMR) does not depend solely on the magnetocaloric effect of their constituents. Rather, it depends on several additional parameters, including, magnetic field, geometry (hydraulic diameter, cross-sectional area, regenerator length etc.), thermal properties (conductivity, specific heat and mass density) and operating parameters (utilization, frequency, number of transfer units etc.). In this paper we focus on the influence of three parameters on regenerator performance: 1) Solid thermal conductivity, 2) magnetostatic demagnetization and 3) flow maldistribution due to geometrically non-uniform regenerators. It is shown that the AMR performance is optimal at an intermediate value of the solid thermal conductivity for many operating conditions. The magnetostatic demagnetization is shown to have a significant influence on the AMR performance, giving a strong dependence on the orientation of the applied field and the regenerator geometry. Finally, the flow maldistribution of non-uniform regenerator geometries is found to degrade the AMR performance even at minor deviations from perfectly homogeneous regenerator matrices. This paper reflects a summary of various recently published results. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002569
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 135–146
Titre : Fluid choice and test standardization for magnetic regenerators operating at near room temperature Titre original : Choix du frigorigène et normalisation des essais pour les régénérateurs fonctionnant à température ambiante Type de document : texte imprimé Auteurs : Jianghong Wu, Auteur ; Chaopeng, Liu, Auteur ; Puxiu, Hou, Auteur Année de publication : 2014 Article en page(s) : pp. 135–146 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; simulation; regenerator; optimization; performance Résumé : Numerical simulations are performed to investigate the performance of an active magnetic regenerator (AMR) operating near room temperature. A two-dimensional porous model is established to analyze the impact different heat transfer fluids (HTFs) have on the performance of the AMR. The internal temperature distribution and cooling capacity of the system are analyzed and the influence of the HTF discussed. The simulation results show that when mercury is substituted in place of water as the HTF, the cooling capacity can be enhanced by nearly 600%. A fluid with high conductivity, high density, and low specific heat is most suitable for use as the HTF. Furthermore, as the environmental conditions have a great impact upon the performance of the AMR, three feasible methods of standardization testing are proposed. These involve: the evaluation index under fixed test environment conditions, a maximum exergy method, and a maximum specific exergy method around the Curie temperature. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002570 [article] Fluid choice and test standardization for magnetic regenerators operating at near room temperature = Choix du frigorigène et normalisation des essais pour les régénérateurs fonctionnant à température ambiante [texte imprimé] / Jianghong Wu, Auteur ; Chaopeng, Liu, Auteur ; Puxiu, Hou, Auteur . - 2014 . - pp. 135–146.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 135–146
Mots-clés : Magnetic refrigeration; simulation; regenerator; optimization; performance Résumé : Numerical simulations are performed to investigate the performance of an active magnetic regenerator (AMR) operating near room temperature. A two-dimensional porous model is established to analyze the impact different heat transfer fluids (HTFs) have on the performance of the AMR. The internal temperature distribution and cooling capacity of the system are analyzed and the influence of the HTF discussed. The simulation results show that when mercury is substituted in place of water as the HTF, the cooling capacity can be enhanced by nearly 600%. A fluid with high conductivity, high density, and low specific heat is most suitable for use as the HTF. Furthermore, as the environmental conditions have a great impact upon the performance of the AMR, three feasible methods of standardization testing are proposed. These involve: the evaluation index under fixed test environment conditions, a maximum exergy method, and a maximum specific exergy method around the Curie temperature. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002570
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 147–155
Titre : An experimental comparison of four magnetocaloric regenerators using three different materials Titre original : Une comparaison expérimentale de quatre régénérateurs magnétocaloriques utilisant trois matériaux différents Type de document : texte imprimé Auteurs : U. Legait, Auteur ; F. Guillou, Auteur ; A. Kedous-Lebouc, Auteur Année de publication : 2014 Article en page(s) : pp. 147–155 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; magnetocaloric regenerator; physical properties; gadolinium; LaFeSiCo; PrSrMnO Résumé : To optimize the performance of an active magnetic regenerative system (AMR), it is important to understand the heat transfer phenomena taking place in the regenerator and the impact of the intrinsic properties of the magnetocaloric material. With this aim in mind, four regenerators involving three different materials (Pr0.65Sr0.35MnO3, La(FeCo)13-xSix, and gadolinium) have been prepared and tested using a permanent magnet based device. This set-up allows studying the performance of different types of regenerators over a wide range of fluidic and magnetic operating conditions. However, since no thermal exchanger is used, this device provides only non-load temperature spans. First, this work deals with an analysis of the performance of the regenerators as a function of their utilization ratio (i.e. working conditions such as the mass flow rate and frequency). Then, an attempt is made to correlate the performance of each regenerator with the physical properties of these different materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001709 [article] An experimental comparison of four magnetocaloric regenerators using three different materials = Une comparaison expérimentale de quatre régénérateurs magnétocaloriques utilisant trois matériaux différents [texte imprimé] / U. Legait, Auteur ; F. Guillou, Auteur ; A. Kedous-Lebouc, Auteur . - 2014 . - pp. 147–155.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 147–155
Mots-clés : Magnetic refrigeration; magnetocaloric regenerator; physical properties; gadolinium; LaFeSiCo; PrSrMnO Résumé : To optimize the performance of an active magnetic regenerative system (AMR), it is important to understand the heat transfer phenomena taking place in the regenerator and the impact of the intrinsic properties of the magnetocaloric material. With this aim in mind, four regenerators involving three different materials (Pr0.65Sr0.35MnO3, La(FeCo)13-xSix, and gadolinium) have been prepared and tested using a permanent magnet based device. This set-up allows studying the performance of different types of regenerators over a wide range of fluidic and magnetic operating conditions. However, since no thermal exchanger is used, this device provides only non-load temperature spans. First, this work deals with an analysis of the performance of the regenerators as a function of their utilization ratio (i.e. working conditions such as the mass flow rate and frequency). Then, an attempt is made to correlate the performance of each regenerator with the physical properties of these different materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001709
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 156–164
Titre : Sizing of a reversible magnetic heat pump for the automotive industry Titre original : Dimensionnement d'une pompe à chaleur magnétique réversible pour l'industrie automobile Type de document : texte imprimé Auteurs : B. Torregrosa-Jaime, Auteur ; J. M. Corberán, Auteur ; C. Vasile, Auteur Année de publication : 2014 Article en page(s) : pp. 156–164 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigerator; heat pump; automobile; air conditioning; modelling Résumé : This paper focuses on the design of an innovative air-conditioning system, namely a magnetocaloric air-conditioner for an electric minibus. An integrated design of the complete system is necessary, as the hot and cold side of the regenerator will work under dynamic conditions which depend on the instantaneous thermal load in the cabin.
In order to assist the design of the system, a dynamic model has been developed for the cabin, the hydraulic loops and heat exchangers, and the magnetocaloric unit. This paper presents (i) a description of the dynamic models, (ii) an analysis of the operating conditions of the magnetocaloric unit and (iii) a discussion on the design of the magnetocaloric air-conditioner. The results show that the electric minibus requests 1.60 kW of cooling power over a span of 37 K in cooling mode, and 3.39 kW of heating power over a span of 40 K.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001771 [article] Sizing of a reversible magnetic heat pump for the automotive industry = Dimensionnement d'une pompe à chaleur magnétique réversible pour l'industrie automobile [texte imprimé] / B. Torregrosa-Jaime, Auteur ; J. M. Corberán, Auteur ; C. Vasile, Auteur . - 2014 . - pp. 156–164.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 156–164
Mots-clés : Magnetic refrigerator; heat pump; automobile; air conditioning; modelling Résumé : This paper focuses on the design of an innovative air-conditioning system, namely a magnetocaloric air-conditioner for an electric minibus. An integrated design of the complete system is necessary, as the hot and cold side of the regenerator will work under dynamic conditions which depend on the instantaneous thermal load in the cabin.
In order to assist the design of the system, a dynamic model has been developed for the cabin, the hydraulic loops and heat exchangers, and the magnetocaloric unit. This paper presents (i) a description of the dynamic models, (ii) an analysis of the operating conditions of the magnetocaloric unit and (iii) a discussion on the design of the magnetocaloric air-conditioner. The results show that the electric minibus requests 1.60 kW of cooling power over a span of 37 K in cooling mode, and 3.39 kW of heating power over a span of 40 K.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001771
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 165–175
Titre : Magnetic heat pumps : configurable hydraulic distribution for a magnetic cooling system=Distribution hydraulique configurable pour un système de froid magnétique Titre original : Pompe à chaleur magnétiques Type de document : texte imprimé Auteurs : J. M. Gatti, Auteur ; C. Muller, Auteur ; C. Vasile, Auteur Année de publication : 2014 Article en page(s) : pp. 165–175 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric heat pump; hydraulic distribution; linear system; rotary system; AMRR cycle; dynamic seal Résumé : Magnetic cooling technology has experienced significant developments over the last five years. Most of the magneto-caloric prototypes use magneto-caloric alloys subject to variable magnetic field and coolant flow synchronized with the magnetisation/demagnetisation cycles. Hydraulic flow regulation has a major impact on the AMRR cycle and on the performance of the magnetic heat pump. This paper discloses a hydraulic solution implemented in a two stage linear prototype, where the volume, the flow rate and the coolant velocity can be controlled.
The dynamic sealing of the system is also described, as well as the performance of a two stage prototype integrating this hydraulic distribution solution to this first generation solution. A brief description of a third generation ‘rotative’ architecture is provided, with results obtained just after the last Thermag V conference.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002399 [article] Magnetic heat pumps = Pompe à chaleur magnétiques : configurable hydraulic distribution for a magnetic cooling system=Distribution hydraulique configurable pour un système de froid magnétique [texte imprimé] / J. M. Gatti, Auteur ; C. Muller, Auteur ; C. Vasile, Auteur . - 2014 . - pp. 165–175.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 165–175
Mots-clés : Magnetocaloric heat pump; hydraulic distribution; linear system; rotary system; AMRR cycle; dynamic seal Résumé : Magnetic cooling technology has experienced significant developments over the last five years. Most of the magneto-caloric prototypes use magneto-caloric alloys subject to variable magnetic field and coolant flow synchronized with the magnetisation/demagnetisation cycles. Hydraulic flow regulation has a major impact on the AMRR cycle and on the performance of the magnetic heat pump. This paper discloses a hydraulic solution implemented in a two stage linear prototype, where the volume, the flow rate and the coolant velocity can be controlled.
The dynamic sealing of the system is also described, as well as the performance of a two stage prototype integrating this hydraulic distribution solution to this first generation solution. A brief description of a third generation ‘rotative’ architecture is provided, with results obtained just after the last Thermag V conference.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002399
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 176-184
Titre : High-frequency magnetocaloric modules with heat gates operating with the Peltier effect Titre original : Modules magnétocaloriques à haute fréquence munis d'interrupteurs thermiques fonctionnant grâce à l'effet Peltier Type de document : texte imprimé Auteurs : Peter W. Egolf, Auteur ; L. Gravier, Auteur ; T. Francfort, Auteur Année de publication : 2014 Article en page(s) : pp. 176-184 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocalorics; magnetic refrigeration; thermal switches; Peltier elements; seebeck effect; high-frequency Résumé : Magnetic heat pumps, refrigerators and energy conversion prototypes, with an operation based on the magnetocaloric effect, usually show a restriction in their frequency of operation to a few Hertz. In 2010 it was proposed to apply thermal switches to overcome this barrier. In this article thermal switches built with Ni-nanowire Peltier elements are presented and the performance of such elements is discussed on a theoretical and experimental basis. Finally an approximate estimate of the performance of a magnetic refrigerator of the types built up to present is compared to that of a magnetic refrigerator applying nanowire thermal switches. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002624 [article] High-frequency magnetocaloric modules with heat gates operating with the Peltier effect = Modules magnétocaloriques à haute fréquence munis d'interrupteurs thermiques fonctionnant grâce à l'effet Peltier [texte imprimé] / Peter W. Egolf, Auteur ; L. Gravier, Auteur ; T. Francfort, Auteur . - 2014 . - pp. 176-184.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 176-184
Mots-clés : Magnetocalorics; magnetic refrigeration; thermal switches; Peltier elements; seebeck effect; high-frequency Résumé : Magnetic heat pumps, refrigerators and energy conversion prototypes, with an operation based on the magnetocaloric effect, usually show a restriction in their frequency of operation to a few Hertz. In 2010 it was proposed to apply thermal switches to overcome this barrier. In this article thermal switches built with Ni-nanowire Peltier elements are presented and the performance of such elements is discussed on a theoretical and experimental basis. Finally an approximate estimate of the performance of a magnetic refrigerator of the types built up to present is compared to that of a magnetic refrigerator applying nanowire thermal switches. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002624
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 185–193
Titre : A numerical comparison of a parallel-plate AMR and a magnetocaloric device with embodied micro thermoelectric thermal diodes Titre original : Une comparaison numérique de plaques de régénérateurs magnétiques actifs (AMR) paralléles et d'un appareil magnétocalorique avec à micro-diodes thermiques et thermoélectriques incorporées Type de document : texte imprimé Auteurs : Urban Tomc, Auteur ; Jaka Tušek, Auteur ; Andrej Kitanovski, Auteur Année de publication : 2014 Article en page(s) : pp. 185–193 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetic refrigeration; active magnetic regenerator; thermal diodes; effet Peltier; heat transfer Résumé : This article introduces a novel heat-transfer mechanism for magnetocaloric energy conversion based on the introduction of thermoelectric thermal diodes. These can provide the very rapid transport of heat from/to the magnetocaloric material. For the purposes of the study, a new mathematical-numerical model has been developed. The model serves for dynamic heat-transfer simulations and an estimation of the cooling characteristics of magnetocaloric devices, which apply thermal diodes. Micro Peltier elements were considered as the thermal diodes. A theoretical analysis was performed in order to compare the performance of a parallel-plate active magnetic regenerator with a magnetocaloric device that uses thermal diodes. The results show the great potential for magnetocaloric devices with thermal diodes, especially in terms of an increased operating frequency and specific cooling powers. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001679 [article] A numerical comparison of a parallel-plate AMR and a magnetocaloric device with embodied micro thermoelectric thermal diodes = Une comparaison numérique de plaques de régénérateurs magnétiques actifs (AMR) paralléles et d'un appareil magnétocalorique avec à micro-diodes thermiques et thermoélectriques incorporées [texte imprimé] / Urban Tomc, Auteur ; Jaka Tušek, Auteur ; Andrej Kitanovski, Auteur . - 2014 . - pp. 185–193.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 185–193
Mots-clés : Magnetic refrigeration; active magnetic regenerator; thermal diodes; effet Peltier; heat transfer Résumé : This article introduces a novel heat-transfer mechanism for magnetocaloric energy conversion based on the introduction of thermoelectric thermal diodes. These can provide the very rapid transport of heat from/to the magnetocaloric material. For the purposes of the study, a new mathematical-numerical model has been developed. The model serves for dynamic heat-transfer simulations and an estimation of the cooling characteristics of magnetocaloric devices, which apply thermal diodes. Micro Peltier elements were considered as the thermal diodes. A theoretical analysis was performed in order to compare the performance of a parallel-plate active magnetic regenerator with a magnetocaloric device that uses thermal diodes. The results show the great potential for magnetocaloric devices with thermal diodes, especially in terms of an increased operating frequency and specific cooling powers. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001679
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 194–200
Titre : Modeling of in-vehicle magnetic refrigeration Titre original : Modèlisation du froid magnétique pour véhicules Type de document : texte imprimé Auteurs : U. L. Olsen, Auteur ; C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur Année de publication : 2014 Article en page(s) : pp. 194–200 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Active magnetic regenerator; thermal switch; numerical model; magnetic refrigeration Résumé : A high-performance magnetic refrigeration device is considered as a potential technology for in-vehicle air conditioners in electric vehicles. The high power consumption of a conventional air conditioner in an electric vehicle has considerable impacts on cruising distance. For this purpose the demands on cooling power density, temperature difference between hot and cold side, transient properties and COP, will be high. In this paper the potential to reach these demands are explored for two technologies, firstly a conventional AMR device and secondly a novel magnetocaloric device based on control of the axial thermal conductivity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002478 [article] Modeling of in-vehicle magnetic refrigeration = Modèlisation du froid magnétique pour véhicules [texte imprimé] / U. L. Olsen, Auteur ; C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur . - 2014 . - pp. 194–200.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 194–200
Mots-clés : Active magnetic regenerator; thermal switch; numerical model; magnetic refrigeration Résumé : A high-performance magnetic refrigeration device is considered as a potential technology for in-vehicle air conditioners in electric vehicles. The high power consumption of a conventional air conditioner in an electric vehicle has considerable impacts on cruising distance. For this purpose the demands on cooling power density, temperature difference between hot and cold side, transient properties and COP, will be high. In this paper the potential to reach these demands are explored for two technologies, firstly a conventional AMR device and secondly a novel magnetocaloric device based on control of the axial thermal conductivity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002478
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 201-208
Titre : Experimental study of a static system based on a magneto-thermal coupling in ferrofluids Titre original : Étude expérimentale d'une pompe statique fondée sur le couplage magnéto-thermique au sein des ferrofluides Type de document : texte imprimé Auteurs : M. Petit, Auteur ; Avenas, Yvan, Auteur ; A. Kedous-Lebouc, Auteur Année de publication : 2014 Article en page(s) : pp. 201-208 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Low Curie temperature ferrofluids; static pump; magnetothermal coupling; power electronics cooling Résumé : Liquid cooling of electronic devices requires generally a mechanical pump which reduces the performance of the system and its reliability. It has already been shown that ferrofluids with low Curie temperature are able to create a liquid flow without any mechanical part. In fact a pressure gradient can be obtained when subjecting this ferrofluids to both a temperature gradient and a magnetic field. In this paper a novel experimental setup is proposed. It is thermally and magnetically instrumented to achieve a precise analysis of the local behavior of the ferrofluids. A MnZn based ferrofluid was investigated on steady and transient states. The results confirm that a hydrostatic pressure can be successfully created. The behavior of the ferrofluid is analyzed considering a homogeneous applied magnetic field or not. A pressure drop is also highlighted and discussed in terms of temperature gradient evolution and magneto-convection in the ferrofluid. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002454 [article] Experimental study of a static system based on a magneto-thermal coupling in ferrofluids = Étude expérimentale d'une pompe statique fondée sur le couplage magnéto-thermique au sein des ferrofluides [texte imprimé] / M. Petit, Auteur ; Avenas, Yvan, Auteur ; A. Kedous-Lebouc, Auteur . - 2014 . - pp. 201-208.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 201-208
Mots-clés : Low Curie temperature ferrofluids; static pump; magnetothermal coupling; power electronics cooling Résumé : Liquid cooling of electronic devices requires generally a mechanical pump which reduces the performance of the system and its reliability. It has already been shown that ferrofluids with low Curie temperature are able to create a liquid flow without any mechanical part. In fact a pressure gradient can be obtained when subjecting this ferrofluids to both a temperature gradient and a magnetic field. In this paper a novel experimental setup is proposed. It is thermally and magnetically instrumented to achieve a precise analysis of the local behavior of the ferrofluids. A MnZn based ferrofluid was investigated on steady and transient states. The results confirm that a hydrostatic pressure can be successfully created. The behavior of the ferrofluid is analyzed considering a homogeneous applied magnetic field or not. A pressure drop is also highlighted and discussed in terms of temperature gradient evolution and magneto-convection in the ferrofluid. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002454
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 209-214
Titre : A heat transfer study aiming optimization of magnetic heat exchangers of thermomagnetic motors Titre original : Une étude sur le transfert de chaleur pour optimiser les échangeurs de chaleur magnétiques des moteurs thermomagnétiques Type de document : texte imprimé Auteurs : L. D. R. Ferreira, Auteur ; C. V. X. Bessa, Auteur ; I. da Silva, Auteur Année de publication : 2014 Article en page(s) : pp. 209-214 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Thermomagnetic; CFD; magnetocaloric; heat exchangers; sustainability Résumé : One prototype of a linear reciprocating thermomagnetic motor designed to work with hot water obtained from plane solar collectors as a hot source and water at room temperature as cold source has been under development. In this motor, the force element is composed of an arrangement of permanent magnets and by two plates of magnetic material having a Curie temperature midway between the temperatures of the hot and cold sources. The magnetic material plates work as motor's heat exchangers, and are shaped in form of parallelepipedal plates with internal channels. As the power to be obtained from the motor is a direct function of its operating frequency or velocity, it is important to have an optimized design of the heat exchanger channels. We report in this work the optimization procedures performed using CFD software (Computational Fluid Dynamics) aiming to maximize the heat exchangers transfer rate. The mentioned linear reciprocating motor that has been under development is not reported here. It will be presented in another work for convenience. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002442 [article] A heat transfer study aiming optimization of magnetic heat exchangers of thermomagnetic motors = Une étude sur le transfert de chaleur pour optimiser les échangeurs de chaleur magnétiques des moteurs thermomagnétiques [texte imprimé] / L. D. R. Ferreira, Auteur ; C. V. X. Bessa, Auteur ; I. da Silva, Auteur . - 2014 . - pp. 209-214.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 209-214
Mots-clés : Thermomagnetic; CFD; magnetocaloric; heat exchangers; sustainability Résumé : One prototype of a linear reciprocating thermomagnetic motor designed to work with hot water obtained from plane solar collectors as a hot source and water at room temperature as cold source has been under development. In this motor, the force element is composed of an arrangement of permanent magnets and by two plates of magnetic material having a Curie temperature midway between the temperatures of the hot and cold sources. The magnetic material plates work as motor's heat exchangers, and are shaped in form of parallelepipedal plates with internal channels. As the power to be obtained from the motor is a direct function of its operating frequency or velocity, it is important to have an optimized design of the heat exchanger channels. We report in this work the optimization procedures performed using CFD software (Computational Fluid Dynamics) aiming to maximize the heat exchangers transfer rate. The mentioned linear reciprocating motor that has been under development is not reported here. It will be presented in another work for convenience. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002442
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 215–222
Titre : Simulation of solar Curie wheel using NiFe alloy and Gd Titre original : Simulation d'une roue solaire de Curie utilisant un alliage de NiFe et de Gd Type de document : texte imprimé Auteurs : C. S. Alves, Auteur ; F. C. Colman, Auteur ; G. L. Foleiss, Auteur Année de publication : 2014 Article en page(s) : pp. 215–222 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Solar energy; thermomagnetic motor; curie wheel; finite difference method Résumé : The increasing demand for energy has driven society to explore different sources of energy, seeking to achieve sustainability. In this sense, we designed a thermal machine whose energy source is solar, which was based on the working principle of the Curie thermomagnetic motor. Thus this paper describes the modeling and simulation of a Curie wheel. Two materials were analyzed for the rotor, 30% NiFe alloy and Gd. The heat transfer inherent to the conversion process of solar energy and natural convection were studied, utilizing a one-dimensional finite difference model linked with the rotor magnetization in the magnetic circuit. We verified that for both materials the best performance was achieved with a convection coefficient of 10 W m−2 K−1. Furthermore, Gd offers about one order of magnitude greater efficiency when compared to the 30% NiFe alloy, but unfortunately the actual value is still too small to be commercially implementable. Nevertheless, this result indicates that better magnetic materials with Curie temperatures slightly above ambient are the key to achieving higher efficiencies, and, accordingly, magnetocaloric materials research has much to add. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300265X [article] Simulation of solar Curie wheel using NiFe alloy and Gd = Simulation d'une roue solaire de Curie utilisant un alliage de NiFe et de Gd [texte imprimé] / C. S. Alves, Auteur ; F. C. Colman, Auteur ; G. L. Foleiss, Auteur . - 2014 . - pp. 215–222.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 215–222
Mots-clés : Solar energy; thermomagnetic motor; curie wheel; finite difference method Résumé : The increasing demand for energy has driven society to explore different sources of energy, seeking to achieve sustainability. In this sense, we designed a thermal machine whose energy source is solar, which was based on the working principle of the Curie thermomagnetic motor. Thus this paper describes the modeling and simulation of a Curie wheel. Two materials were analyzed for the rotor, 30% NiFe alloy and Gd. The heat transfer inherent to the conversion process of solar energy and natural convection were studied, utilizing a one-dimensional finite difference model linked with the rotor magnetization in the magnetic circuit. We verified that for both materials the best performance was achieved with a convection coefficient of 10 W m−2 K−1. Furthermore, Gd offers about one order of magnitude greater efficiency when compared to the 30% NiFe alloy, but unfortunately the actual value is still too small to be commercially implementable. Nevertheless, this result indicates that better magnetic materials with Curie temperatures slightly above ambient are the key to achieving higher efficiencies, and, accordingly, magnetocaloric materials research has much to add. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300265X
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 223–229
Titre : Recent progress in magnetocaloric effect: Mechanisms and potential applications Titre original : Progrès récents dans l'effet magnétocalorique : mécanismes et applications potentielles Type de document : texte imprimé Auteurs : A. M. Tishin, Auteur ; Y. I. Spichkin, Auteur Année de publication : 2014 Article en page(s) : pp. 223–229 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; thermodynamic model; magnetic entropy Résumé : Recent results in understanding of the magnetocaloric effect (MCE) mechanisms in the framework of thermodynamic approach are regarded and discussed. Importance of relation between ΔSMT (magnetic entropy change at constant temperature) and ΔSMH (magnetic entropy change at constant field) and it influence on MCE value is considered. The main contributions to the MCE are discussed. The importance of further development of models of interactions between magnetic and structural subsystems in vicinity of magnetic phase transitions is stressed. It is stated that the present level of MCE parameters (in particular, adiabatic temperature change) can be increased up to 3 times. The necessity of investigation of MCE parameters in dynamic mode and development of new experimental methods and apparatuses for MCE measurements is discussed. The most obvious application for MCE for today is magnetic refrigeration, but MCE also can be used for other applications such as medicine (hyperthermia, drug delivering), etc., which are regarded. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002466 [article] Recent progress in magnetocaloric effect: Mechanisms and potential applications = Progrès récents dans l'effet magnétocalorique : mécanismes et applications potentielles [texte imprimé] / A. M. Tishin, Auteur ; Y. I. Spichkin, Auteur . - 2014 . - pp. 223–229.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 223–229
Mots-clés : Magnetocaloric effect; thermodynamic model; magnetic entropy Résumé : Recent results in understanding of the magnetocaloric effect (MCE) mechanisms in the framework of thermodynamic approach are regarded and discussed. Importance of relation between ΔSMT (magnetic entropy change at constant temperature) and ΔSMH (magnetic entropy change at constant field) and it influence on MCE value is considered. The main contributions to the MCE are discussed. The importance of further development of models of interactions between magnetic and structural subsystems in vicinity of magnetic phase transitions is stressed. It is stated that the present level of MCE parameters (in particular, adiabatic temperature change) can be increased up to 3 times. The necessity of investigation of MCE parameters in dynamic mode and development of new experimental methods and apparatuses for MCE measurements is discussed. The most obvious application for MCE for today is magnetic refrigeration, but MCE also can be used for other applications such as medicine (hyperthermia, drug delivering), etc., which are regarded. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002466
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 230-236
Titre : Experimental methods of the magnetocaloric effect studies Titre original : Méthodes expérimentales pour l'étude de l'effet magnétocalorique Type de document : texte imprimé Auteurs : Y. I. Spichkin, Auteur ; R. R. Gimaev, Auteur Année de publication : 2014 Article en page(s) : pp. 230-236 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; magnetic refrigeration; measurements; indirect methods; dynamic magnetocaloric; direct methods Résumé : The methods of experimental investigations of the magnetocaloric parameters (adiabatic temperature change and isothermal magnetic entropy change caused by external magnetic field) are reviewed and discussed. The direct and indirect methods are compared and their advantages and disadvantages are considered. Possible influence of the used methods on the obtained results is regarded. The main attention is paid to the direct methods of measurements. The realization of the dynamic mode of the direct adiabatic temperature change measurement is considered. Importance of the magnetocaloric measurements in dynamic mode for characterization of the magnetocaloric materials suitable for using as working bodies in magnetic heat machines is shown. The methods of the experimental data processing are discussed. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002521 [article] Experimental methods of the magnetocaloric effect studies = Méthodes expérimentales pour l'étude de l'effet magnétocalorique [texte imprimé] / Y. I. Spichkin, Auteur ; R. R. Gimaev, Auteur . - 2014 . - pp. 230-236.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 230-236
Mots-clés : Magnetocaloric effect; magnetic refrigeration; measurements; indirect methods; dynamic magnetocaloric; direct methods Résumé : The methods of experimental investigations of the magnetocaloric parameters (adiabatic temperature change and isothermal magnetic entropy change caused by external magnetic field) are reviewed and discussed. The direct and indirect methods are compared and their advantages and disadvantages are considered. Possible influence of the used methods on the obtained results is regarded. The main attention is paid to the direct methods of measurements. The realization of the dynamic mode of the direct adiabatic temperature change measurement is considered. Importance of the magnetocaloric measurements in dynamic mode for characterization of the magnetocaloric materials suitable for using as working bodies in magnetic heat machines is shown. The methods of the experimental data processing are discussed. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002521
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 237–248
Titre : Magnetocaloric and barocaloric effects: Theoretical description and trends Titre original : Effets magnétocaloriques et barocaloriques: Description théorique et tendances Type de document : texte imprimé Auteurs : N. A. de Oliveira, Auteur ; P. J. von Ranke, Auteur ; A. Troper, Auteur Année de publication : 2014 Article en page(s) : pp. 237–248 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; barocaloric effect, metal; alloy; thermodynamic modeling Résumé : In this review paper we present a theoretical description of the magnetocaloric and barocaloric effects in metallic compounds. The theoretical formulation is separated in two categories namely, [1] systems whose magnetism is due to localized magnetic moments [2] systems whose magnetism is due to itinerant electrons. In both cases we perform systematic analysis of the magnetocaloric and barocaloric quantities in terms of the model parameters. Besides that, an application has been made to the real compounds 5Tb2Si2GeTb5Si2Ge2 and Mn(As0.7Sb0.3)Mn(As0.7Sb0.3). En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001229 [article] Magnetocaloric and barocaloric effects: Theoretical description and trends = Effets magnétocaloriques et barocaloriques: Description théorique et tendances [texte imprimé] / N. A. de Oliveira, Auteur ; P. J. von Ranke, Auteur ; A. Troper, Auteur . - 2014 . - pp. 237–248.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 237–248
Mots-clés : Magnetocaloric effect; barocaloric effect, metal; alloy; thermodynamic modeling Résumé : In this review paper we present a theoretical description of the magnetocaloric and barocaloric effects in metallic compounds. The theoretical formulation is separated in two categories namely, [1] systems whose magnetism is due to localized magnetic moments [2] systems whose magnetism is due to itinerant electrons. In both cases we perform systematic analysis of the magnetocaloric and barocaloric quantities in terms of the model parameters. Besides that, an application has been made to the real compounds 5Tb2Si2GeTb5Si2Ge2 and Mn(As0.7Sb0.3)Mn(As0.7Sb0.3). En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001229
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 249-256
Titre : On the thermodynamic foundations of solid-state cooler based on multiferroic materials Titre original : Sur les bases thermodynamiques du refroidisseur à l'état solide à base de matériaux multiferroïques Type de document : texte imprimé Auteurs : I. A. Starkov, Auteur ; A. S. Starkov, Auteur Année de publication : 2014 Article en page(s) : pp. 249-256 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Solid-state cooler; multiferroic; multicaloric effect; electrocaloric effect; multilayered cooler Résumé : In this work, we present the theoretical description of thermodynamics of the solid-state cooler based on multiferroic materials. By virtue of the derived equations, we examine the temperature dependence of multiferroic with simultaneous exposure to the periodic electric, magnetic, and elastic fields. The presence of heat exchange with the environment is taken into account. It is demonstrated that the modulation of the applied electric field by magnetic and/or elastic ones can increase the temperature change in 2–3 times in comparison with just the electric field contribution. Additionally, the paper pays careful attention to the layered multiferroic structure. The temperature distribution of this system as a function of position is investigated. The obtained results provide a theoretical basis and physical insights for further development of the efficient solid-state cooler based on multiferroic materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002107 [article] On the thermodynamic foundations of solid-state cooler based on multiferroic materials = Sur les bases thermodynamiques du refroidisseur à l'état solide à base de matériaux multiferroïques [texte imprimé] / I. A. Starkov, Auteur ; A. S. Starkov, Auteur . - 2014 . - pp. 249-256.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 249-256
Mots-clés : Solid-state cooler; multiferroic; multicaloric effect; electrocaloric effect; multilayered cooler Résumé : In this work, we present the theoretical description of thermodynamics of the solid-state cooler based on multiferroic materials. By virtue of the derived equations, we examine the temperature dependence of multiferroic with simultaneous exposure to the periodic electric, magnetic, and elastic fields. The presence of heat exchange with the environment is taken into account. It is demonstrated that the modulation of the applied electric field by magnetic and/or elastic ones can increase the temperature change in 2–3 times in comparison with just the electric field contribution. Additionally, the paper pays careful attention to the layered multiferroic structure. The temperature distribution of this system as a function of position is investigated. The obtained results provide a theoretical basis and physical insights for further development of the efficient solid-state cooler based on multiferroic materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002107
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 257-265
Titre : Entropy change at magnetic phase transitions of the first order and second order Titre original : Changement d'entropie et transitions de la phase magnétique de premier et de second ordre Type de document : texte imprimé Auteurs : Vittorio Basso, Auteur ; Carlo P. Sasso, Auteur ; Michaela Küpferling, Auteur Année de publication : 2014 Article en page(s) : pp. 257-265 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; Gd; La(Fe–Si)13; Heusler alloy Ni–Mn–Co–Sn; mean field theory Résumé : Magnetocaloric properties close to first order and second order phase transitions are presented and discussed. The specific heat capacity as a function of the magnetic field and the magnetic field induced entropy change has been measured by direct heat flux calorimetry in Gd, hydrogenated La(Fe–Mn–Si)13, La(Fe–Co–Si)13 and the Heusler alloy Ni–Mn–Co–Sn. The resulting s(Ha,T) entropy constitutive relation is compared with a model including the ferromagnetic, electronic and structural contributions to the free energy. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001990 [article] Entropy change at magnetic phase transitions of the first order and second order = Changement d'entropie et transitions de la phase magnétique de premier et de second ordre [texte imprimé] / Vittorio Basso, Auteur ; Carlo P. Sasso, Auteur ; Michaela Küpferling, Auteur . - 2014 . - pp. 257-265.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 257-265
Mots-clés : Magnetocaloric effect; Gd; La(Fe–Si)13; Heusler alloy Ni–Mn–Co–Sn; mean field theory Résumé : Magnetocaloric properties close to first order and second order phase transitions are presented and discussed. The specific heat capacity as a function of the magnetic field and the magnetic field induced entropy change has been measured by direct heat flux calorimetry in Gd, hydrogenated La(Fe–Mn–Si)13, La(Fe–Co–Si)13 and the Heusler alloy Ni–Mn–Co–Sn. The resulting s(Ha,T) entropy constitutive relation is compared with a model including the ferromagnetic, electronic and structural contributions to the free energy. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001990
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 266–272
Titre : Entropy change and kinetic effects at the magnetostructural phase transition of MnBi Titre original : Changement d'entropie et effets cinétiques à la transition de phase magnétostructurelle de MnBi Type de document : texte imprimé Auteurs : Vittorio Basso, Auteur ; Elena Sonia Olivetti, Auteur ; Luca Martino, Auteur Année de publication : 2014 Article en page(s) : pp. 266–272 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; MnBi; kinetic effects; first order phase transition Résumé : In this paper we investigate the entropy change and the kinetics at the magneto-structural transition (at 628 K) of polycrystalline MnBi. Samples were prepared by rapid quenching and annealing and exhibit 86 wt% of the hexagonal MnBi phase. The entropy change at the transition is found to be Δs = 17.6 J kg−1 K−1 and the magnetic field shifts the transition temperature at a rate of 2.6 K T−1. The temperature hysteresis, of 19 K, is quite large for magneto-thermal application. The transition shows kinetics effects upon cooling in which the transition temperature is found to depend approximately to the logarithm of the temperature rate with coefficient −3.8 K. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001783 [article] Entropy change and kinetic effects at the magnetostructural phase transition of MnBi = Changement d'entropie et effets cinétiques à la transition de phase magnétostructurelle de MnBi [texte imprimé] / Vittorio Basso, Auteur ; Elena Sonia Olivetti, Auteur ; Luca Martino, Auteur . - 2014 . - pp. 266–272.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 266–272
Mots-clés : Magnetocaloric effect; MnBi; kinetic effects; first order phase transition Résumé : In this paper we investigate the entropy change and the kinetics at the magneto-structural transition (at 628 K) of polycrystalline MnBi. Samples were prepared by rapid quenching and annealing and exhibit 86 wt% of the hexagonal MnBi phase. The entropy change at the transition is found to be Δs = 17.6 J kg−1 K−1 and the magnetic field shifts the transition temperature at a rate of 2.6 K T−1. The temperature hysteresis, of 19 K, is quite large for magneto-thermal application. The transition shows kinetics effects upon cooling in which the transition temperature is found to depend approximately to the logarithm of the temperature rate with coefficient −3.8 K. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001783
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 273–280
Titre : Tuning magnetic exchange interactions to enhance magnetocaloric effect in Ni50Mn34In16 Heusler alloy: Monte Carlo and ab initio studies Titre original : Réglage des interactions d'échange magnétique pour améliorer l'effet magnétocalorique dans l'alliage de Heusler NI50Mn34In16 : études de Monte Carlo et initiales Type de document : texte imprimé Auteurs : V. V. Sokolovskiy, Auteur ; V. D. Buchelnikov, Auteur ; V. V. Khovaylo, Auteur Année de publication : 2014 Article en page(s) : pp. 273–280 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Heulser alloys; magnetocaloric effect; ferromagnetic – antiferromagnetic interaction; Monte Carlo method Résumé : Influence of the strength of magnetic exchange interactions and impact of a ferromagnetic-antiferromagnetic exchange competition on magnetocaloric effect in a Ni50Mn34In16 Heusler alloy are studied by a Monte Carlo simulation. Temperature dependencies of magnetic and magnetocaloric properties are obtained in the framework of Potts and Blume-Emery-Griffiths models. It is shown that a decrease of the exchange interactions as well as “switching off” ferromagnetic interactions between the Mn atoms in the martensite favors the inverse magnetocaloric effect in Ni50Mn34In16. Contrary, “switching off” antiferromagnetic interactions depletes the inverse magnetocaloric effect. It is supposed that the exchange interactions in Ni–Mn-In alloys can be tuned favorably by a doping of the host alloys with nonmagnetic or antiferromagnetic atoms, e.g., B, Cu, Cr, etc. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001448 [article] Tuning magnetic exchange interactions to enhance magnetocaloric effect in Ni50Mn34In16 Heusler alloy: Monte Carlo and ab initio studies = Réglage des interactions d'échange magnétique pour améliorer l'effet magnétocalorique dans l'alliage de Heusler NI50Mn34In16 : études de Monte Carlo et initiales [texte imprimé] / V. V. Sokolovskiy, Auteur ; V. D. Buchelnikov, Auteur ; V. V. Khovaylo, Auteur . - 2014 . - pp. 273–280.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 273–280
Mots-clés : Heulser alloys; magnetocaloric effect; ferromagnetic – antiferromagnetic interaction; Monte Carlo method Résumé : Influence of the strength of magnetic exchange interactions and impact of a ferromagnetic-antiferromagnetic exchange competition on magnetocaloric effect in a Ni50Mn34In16 Heusler alloy are studied by a Monte Carlo simulation. Temperature dependencies of magnetic and magnetocaloric properties are obtained in the framework of Potts and Blume-Emery-Griffiths models. It is shown that a decrease of the exchange interactions as well as “switching off” ferromagnetic interactions between the Mn atoms in the martensite favors the inverse magnetocaloric effect in Ni50Mn34In16. Contrary, “switching off” antiferromagnetic interactions depletes the inverse magnetocaloric effect. It is supposed that the exchange interactions in Ni–Mn-In alloys can be tuned favorably by a doping of the host alloys with nonmagnetic or antiferromagnetic atoms, e.g., B, Cu, Cr, etc. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001448
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 281–288
Titre : Inapplicability of the Maxwell relation for the quantification of caloric effects in anisotropic ferroic materials Titre original : Inapplicabilité de la relation de Maxwell pour la quantification des effets calorifiques dans des matériaux ferroïques anisotropiques Type de document : texte imprimé Auteurs : R. Niemann, Auteur ; O. Heczko, Auteur ; L. Schultz, Auteur Année de publication : 2014 Article en page(s) : pp. 281–288 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric; shape memory alloys; multiferroic; Ni-Mn-Ga; Maxwell relation Résumé : Giant caloric effects were reported in elasto-, electro- and magnetocaloric materials near phase transformations. Commonly, their entropy change is indirectly evaluated by a Maxwell relation. Additionally to the well-known spurious “colossal” results near first-order phase transitions and limitations in the presence of magnetic domains, we report the fundamental failure of this approach for materials that show structural reorientations in external fields. We analyze exemplarily the magnetic shape memory alloy Ni-Mn-Ga. Application of a magnetic field causes magnetically induced reorientation of the crystal structure in the martensite phase. This results in a spurious inverse magnetocaloric effect that disappears when the measurement procedure is repeated. This failure is universal as the vector character of the applied field is not considered in the common scalar evaluation of a Maxwell relation. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002314 [article] Inapplicability of the Maxwell relation for the quantification of caloric effects in anisotropic ferroic materials = Inapplicabilité de la relation de Maxwell pour la quantification des effets calorifiques dans des matériaux ferroïques anisotropiques [texte imprimé] / R. Niemann, Auteur ; O. Heczko, Auteur ; L. Schultz, Auteur . - 2014 . - pp. 281–288.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 281–288
Mots-clés : Magnetocaloric; shape memory alloys; multiferroic; Ni-Mn-Ga; Maxwell relation Résumé : Giant caloric effects were reported in elasto-, electro- and magnetocaloric materials near phase transformations. Commonly, their entropy change is indirectly evaluated by a Maxwell relation. Additionally to the well-known spurious “colossal” results near first-order phase transitions and limitations in the presence of magnetic domains, we report the fundamental failure of this approach for materials that show structural reorientations in external fields. We analyze exemplarily the magnetic shape memory alloy Ni-Mn-Ga. Application of a magnetic field causes magnetically induced reorientation of the crystal structure in the martensite phase. This results in a spurious inverse magnetocaloric effect that disappears when the measurement procedure is repeated. This failure is universal as the vector character of the applied field is not considered in the common scalar evaluation of a Maxwell relation. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002314
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 289-296
Titre : Modeling and characterization of the magnetocaloric effect in Ni2MnGa materials Titre original : Modélisation et caractérisation de l'effet magnétocalorique dans les matériaux Ni2MnGa Type de document : texte imprimé Auteurs : D. M. Nicholson, Auteur ; Kh. Odbadrakh, Auteur ; B. A. Shassere, Auteur Année de publication : 2014 Article en page(s) : pp. 289-296 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Ni2MnGa; magnetocaloric; magnetic entropy; elastic neutron scattering; first principles Résumé : Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300279X [article] Modeling and characterization of the magnetocaloric effect in Ni2MnGa materials = Modélisation et caractérisation de l'effet magnétocalorique dans les matériaux Ni2MnGa [texte imprimé] / D. M. Nicholson, Auteur ; Kh. Odbadrakh, Auteur ; B. A. Shassere, Auteur . - 2014 . - pp. 289-296.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 289-296
Mots-clés : Ni2MnGa; magnetocaloric; magnetic entropy; elastic neutron scattering; first principles Résumé : Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300279X
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 297-302
Titre : Magnetocaloric effect in Gd(1−y)DyyAl2 Titre original : Effet magnétocalorique dans du Gd(1Ly)DyyAl2 Type de document : texte imprimé Auteurs : B. P. Alho, Auteur ; P. O. Ribeiro, Auteur ; T. S. T. Alvarenga, Auteur Année de publication : 2014 Article en page(s) : pp. 297-302 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; composite; rare-earth; crystalline anisotropy Résumé : In this work we calculate the magnetic properties and the magnetocaloric effect in Gd1−yDyyAl2 (y = 0, 0.25, 0.5, 0.75 and 1). The model Hamiltonian includes contributions from the Zeeman effect, the crystalline electrical field anisotropy and the exchange interactions among Gd–Gd, Gd–Dy and Dy–Dy ions. To obtain a composite with ΔST as constant as possible in the temperature range from T = 60 K to 170 K, the appropriate concentrations of the five compounds investigated were calculated using the Smaili and Chahine method. The magnetization and ΔST dependences on temperature in the composite were simulated and compared with the partial contributions of the single magnetic component materials. Also, the magnetic field dependence on magnetization was investigated in Gd0.25Dy0.75Al2, where the discontinuous spin reorientation transitions were predicted for magnetic fields lower than 2 T, applied along <110> direction. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300176X [article] Magnetocaloric effect in Gd(1−y)DyyAl2 = Effet magnétocalorique dans du Gd(1Ly)DyyAl2 [texte imprimé] / B. P. Alho, Auteur ; P. O. Ribeiro, Auteur ; T. S. T. Alvarenga, Auteur . - 2014 . - pp. 297-302.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 297-302
Mots-clés : Magnetocaloric effect; composite; rare-earth; crystalline anisotropy Résumé : In this work we calculate the magnetic properties and the magnetocaloric effect in Gd1−yDyyAl2 (y = 0, 0.25, 0.5, 0.75 and 1). The model Hamiltonian includes contributions from the Zeeman effect, the crystalline electrical field anisotropy and the exchange interactions among Gd–Gd, Gd–Dy and Dy–Dy ions. To obtain a composite with ΔST as constant as possible in the temperature range from T = 60 K to 170 K, the appropriate concentrations of the five compounds investigated were calculated using the Smaili and Chahine method. The magnetization and ΔST dependences on temperature in the composite were simulated and compared with the partial contributions of the single magnetic component materials. Also, the magnetic field dependence on magnetization was investigated in Gd0.25Dy0.75Al2, where the discontinuous spin reorientation transitions were predicted for magnetic fields lower than 2 T, applied along <110> direction. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071300176X
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 303-306
Titre : Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device Titre original : Étude expérimentale sur l'effet de l'hystérésis thermique sur un matériau MnFe(P,As) de premier ordre, appliqués à un dispositif à régénération active magnétique Type de document : texte imprimé Auteurs : L. von Moos, Auteur ; K.K. Nielsen, Auteur ; K. Engelbrecht, Auteur Année de publication : 2014 Article en page(s) : pp. 303-306 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Magnetocaloric effect; first-order material; hysteresis; magnetic refrigeration; MnFe(P,As) Résumé : The magnetocaloric first order material MnFe(P,As) is a candidate for room temperature magnetic refrigeration. However, these materials have intrinsic hysteresis and the impact on the refrigeration performance has not yet been thoroughly investigated in the literature.
Here, the magnetocaloric effect (MCE) and the thermal hysteresis are studied using vibrating sample magnetometry. The influence on actual refrigeration performance is investigated with an established active magnetic regenerator (AMR) test device (Bahl et al., 2008), utilizing a flat plate regenerator of a single Curie temperature material.
We find that the MCE curves are shifted 1.5 K when comparing heating and cooling the material, while the maximum MCE remains constant. The width of the MCE curve peak is seen to increase 0.3 K when cooling compared to heating. These results are confirmed by experiments on the AMR test device.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001163 [article] Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device = Étude expérimentale sur l'effet de l'hystérésis thermique sur un matériau MnFe(P,As) de premier ordre, appliqués à un dispositif à régénération active magnétique [texte imprimé] / L. von Moos, Auteur ; K.K. Nielsen, Auteur ; K. Engelbrecht, Auteur . - 2014 . - pp. 303-306.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 303-306
Mots-clés : Magnetocaloric effect; first-order material; hysteresis; magnetic refrigeration; MnFe(P,As) Résumé : The magnetocaloric first order material MnFe(P,As) is a candidate for room temperature magnetic refrigeration. However, these materials have intrinsic hysteresis and the impact on the refrigeration performance has not yet been thoroughly investigated in the literature.
Here, the magnetocaloric effect (MCE) and the thermal hysteresis are studied using vibrating sample magnetometry. The influence on actual refrigeration performance is investigated with an established active magnetic regenerator (AMR) test device (Bahl et al., 2008), utilizing a flat plate regenerator of a single Curie temperature material.
We find that the MCE curves are shifted 1.5 K when comparing heating and cooling the material, while the maximum MCE remains constant. The width of the MCE curve peak is seen to increase 0.3 K when cooling compared to heating. These results are confirmed by experiments on the AMR test device.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001163
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 307-313
Titre : Corrosion behavior of gadolinium and La–Fe–Co–Si compounds in various heat conducting fluids Titre original : Comportement de corrosion du gadolinium et de composés de La-Fe-Co-Si dans divers fluides thermoconducteurs Type de document : texte imprimé Auteurs : J. Forchelet, Auteur ; L. Zamni, Auteur ; S. El Maudni El Alami, Auteur Année de publication : 2014 Article en page(s) : pp. 307-313 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Corrosion; magnetic materials; LaFeCoSi compounds; gadolinium; magnetic refrigeration Résumé : For successful implementation in magnetic refrigeration systems, the corrosion resistance of gadolinium and La–Fe–Co–Si compounds in different heat conducting fluids has been studied. Two types of tests were used: immersion at room temperature (ASTM G31-72), and accelerated tests at 88 °C during 336 h (ASTM D1384-05). Results were evaluated regarding corrosion and specific heat: the main objective was to increase the heat transfer and to reduce the corrosion rate. We have also tested a protection of gadolinium by passivation with oxalic acid solutions of pH lower than 1.00. This treatment is efficient, and doesn't affect the magnetocaloric effect. Finally, the optimal solutions were selected and proposed for use by thermal engineers. Passivation can be a good solution to protect gadolinium from corrosion but the use of water based fluids with oxygen inhibitors is better. Some fluids (water + additives) gives satisfaction, providing a heat transfer close to that of water and protecting well materials from corrosion. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002557 [article] Corrosion behavior of gadolinium and La–Fe–Co–Si compounds in various heat conducting fluids = Comportement de corrosion du gadolinium et de composés de La-Fe-Co-Si dans divers fluides thermoconducteurs [texte imprimé] / J. Forchelet, Auteur ; L. Zamni, Auteur ; S. El Maudni El Alami, Auteur . - 2014 . - pp. 307-313.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 307-313
Mots-clés : Corrosion; magnetic materials; LaFeCoSi compounds; gadolinium; magnetic refrigeration Résumé : For successful implementation in magnetic refrigeration systems, the corrosion resistance of gadolinium and La–Fe–Co–Si compounds in different heat conducting fluids has been studied. Two types of tests were used: immersion at room temperature (ASTM G31-72), and accelerated tests at 88 °C during 336 h (ASTM D1384-05). Results were evaluated regarding corrosion and specific heat: the main objective was to increase the heat transfer and to reduce the corrosion rate. We have also tested a protection of gadolinium by passivation with oxalic acid solutions of pH lower than 1.00. This treatment is efficient, and doesn't affect the magnetocaloric effect. Finally, the optimal solutions were selected and proposed for use by thermal engineers. Passivation can be a good solution to protect gadolinium from corrosion but the use of water based fluids with oxygen inhibitors is better. Some fluids (water + additives) gives satisfaction, providing a heat transfer close to that of water and protecting well materials from corrosion. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002557
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 314-318
Titre : Description of a differential setup for relaxation microcalorimetry Titre original : Dispositif différentiel pour la microcalorimétrie des contraintes Type de document : texte imprimé Auteurs : J. V. Leitão, Auteur ; P. van Dommelen, Auteur ; F. Naastepad, Auteur Année de publication : 2014 Article en page(s) : pp. 314-318 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Microcalorimetry; magnetocaloric effect; relaxation measurements; specific heat; xensor chips Résumé : A specific heat measuring instrument, with the capacity for the application of magnetic fields up to 9 T, resorting to microcalorimetry chips from the company Xensor Integration, has been successfully assembled and its functioning specifications are reported in the current paper.
With this instrument is it possible to perform specific heat measurements with applied magnetic fields up to 9 T in milligram samples. This offers our group the possibility to calculate the actual adiabatic temperature change of a material, as well as providing reliable and precise information on any phase transition that may be influenced by the application of a magnetic field.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000960 [article] Description of a differential setup for relaxation microcalorimetry = Dispositif différentiel pour la microcalorimétrie des contraintes [texte imprimé] / J. V. Leitão, Auteur ; P. van Dommelen, Auteur ; F. Naastepad, Auteur . - 2014 . - pp. 314-318.
Refrigeration
Langues : Anglais (eng)
in International journal of refrigeration > Vol. 37 N° 1 (Janvier 2014) . - pp. 314-318
Mots-clés : Microcalorimetry; magnetocaloric effect; relaxation measurements; specific heat; xensor chips Résumé : A specific heat measuring instrument, with the capacity for the application of magnetic fields up to 9 T, resorting to microcalorimetry chips from the company Xensor Integration, has been successfully assembled and its functioning specifications are reported in the current paper.
With this instrument is it possible to perform specific heat measurements with applied magnetic fields up to 9 T in milligram samples. This offers our group the possibility to calculate the actual adiabatic temperature change of a material, as well as providing reliable and precise information on any phase transition that may be influenced by the application of a magnetic field.En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000960
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