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A comprehensive parameter study of an active magnetic regenerator using a 2D numerical model / K.K. Nielsen in International journal of refrigeration, Vol. 33 N° 4 (Juin 2010) 

Public ISBD [article]  in International journal of refrigeration > Vol. 33 N° 4 (Juin 2010) . - pp. 753-764 Titre : A comprehensive parameter study of an active magnetic regenerator using a 2D numerical model Titre original : Etude approfondie sur les paramètres des régénérateurs magnétiques actifs à l'aide d'un modèle numérique bidimensionnel Type de document : texte imprimé Auteurs : K.K. Nielsen, Auteur ; C. R. H. Bahl, Auteur ; A. Smith, Auteur Année de publication : 2010 Article en page(s) : pp. 753-764 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Simulation  Performance  Heat  transfer  Heat  exchange  Regenerator  Gadolinium Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A two-dimensional numerical heat transfer model is used to investigate an active magnetic regenerator (AMR) based on parallel plates of magnetocaloric material. A large range of parameter variations are performed to study the optimal AMR. The parameters varied are the plate and channel thicknesses, cycle frequency and fluid movement. These are cast into the non-dimensional units utilization, porosity and number of transfer units (NTU). The cooling capacity vs. temperature span is mapped as a function of these parameters and each configuration is evaluated through the maximum temperature span and exergy. The results show that the optimal AMR should have a utilization in the range 0.2–1 and an NTU higher than 10 and not necessarily more than 30. It is concluded that parallel plate-based regenerators face significant challenges in terms of manufacturability. However, the benefit of parallel plate regenerators is a very low pressure drop, which is needed for high performance. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000058 [article] A comprehensive parameter study of an active magnetic regenerator using a 2D numerical model = Etude approfondie sur les paramètres des régénérateurs magnétiques actifs à l'aide d'un modèle numérique bidimensionnel [texte imprimé] / K.K. Nielsen, Auteur ; C. R. H. Bahl, Auteur ; A. Smith, Auteur . - 2010 . - pp. 753-764. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 4 (Juin 2010) . - pp. 753-764 Mots-clés : Magnetic  refrigerator  Simulation  Performance  Heat  transfer  Heat  exchange  Regenerator  Gadolinium Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A two-dimensional numerical heat transfer model is used to investigate an active magnetic regenerator (AMR) based on parallel plates of magnetocaloric material. A large range of parameter variations are performed to study the optimal AMR. The parameters varied are the plate and channel thicknesses, cycle frequency and fluid movement. These are cast into the non-dimensional units utilization, porosity and number of transfer units (NTU). The cooling capacity vs. temperature span is mapped as a function of these parameters and each configuration is evaluated through the maximum temperature span and exergy. The results show that the optimal AMR should have a utilization in the range 0.2–1 and an NTU higher than 10 and not necessarily more than 30. It is concluded that parallel plate-based regenerators face significant challenges in terms of manufacturability. However, the benefit of parallel plate regenerators is a very low pressure drop, which is needed for high performance. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000058

Design concepts for a continuously rotating active magnetic regenerator / C. R. H. Bahl in International journal of refrigeration, Vol. 34 N° 8 (Décembre 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1792–1796 Titre : Design concepts for a continuously rotating active magnetic regenerator Titre original : Concepts appliqués dans la conception d'un régénérateur actif magnétique en rotation continue Type de document : texte imprimé Auteurs : C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur ; R. Bjørk, Auteur Année de publication : 2012 Article en page(s) : pp. 1792–1796 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Magnet  Design  Optimization  Model Résumé : Design considerations for a prototype magnetic refrigeration device with a continuously rotating AMR are presented. Building the active magnetic regenerator (AMR) from stacks of elongated plates of the perovskite oxide material La0.67Ca0.33−xSrxMn1.05O3, gives both a low pressure drop and allows grading of the Curie temperature along the plates. This may be accomplished by a novel technique where a compositionally-graded material is tape cast in one piece. The magnet assembly is based on a novel design strategy, to create alternating high- and low magnetic field regions within a magnet assembly. Focus is on maximising the magnetic field in the high field regions but also, importantly, minimising the flux in the low field regions. The design is iteratively optimised through 3D finite element magnetostatic modelling. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001873 [article] Design concepts for a continuously rotating active magnetic regenerator = Concepts appliqués dans la conception d'un régénérateur actif magnétique en rotation continue [texte imprimé] / C. R. H. Bahl, Auteur ; K. Engelbrecht, Auteur ; R. Bjørk, Auteur . - 2012 . - pp. 1792–1796. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1792–1796 Mots-clés : Magnetic  refrigerator  Magnet  Design  Optimization  Model Résumé : Design considerations for a prototype magnetic refrigeration device with a continuously rotating AMR are presented. Building the active magnetic regenerator (AMR) from stacks of elongated plates of the perovskite oxide material La0.67Ca0.33−xSrxMn1.05O3, gives both a low pressure drop and allows grading of the Curie temperature along the plates. This may be accomplished by a novel technique where a compositionally-graded material is tape cast in one piece. The magnet assembly is based on a novel design strategy, to create alternating high- and low magnetic field regions within a magnet assembly. Focus is on maximising the magnetic field in the high field regions but also, importantly, minimising the flux in the low field regions. The design is iteratively optimised through 3D finite element magnetostatic modelling. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001873

Determining the minimum mass and cost of a magnetic refrigerator / R. Bjørk in International journal of refrigeration, Vol. 34 N° 8 (Décembre 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1805–1816 Titre : Determining the minimum mass and cost of a magnetic refrigerator Titre original : Détermination de la masse minimale et du coût d'un réfrigérateur magnétique Type de document : texte imprimé Auteurs : R. Bjørk, Auteur ; A. Smith, Auteur ; C. R. H. Bahl, Auteur Année de publication : 2012 Article en page(s) : pp. 1805–1816 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Regenerator  Magnetic  fieldModeling Résumé : An expression is determined for the mass of the magnet and magnetocaloric material needed for a magnetic refrigerator and these are determined using numerical modeling for both parallel plate and packed sphere bed regenerators as function of temperature span and cooling power. As magnetocaloric material Gd or a model material with a constant adiabatic temperature change, representing an infinitely linearly graded refrigeration device, is used. For the magnet a maximum figure of merit magnet or a Halbach cylinder is used. For a cost of $40 and $20 per kg for the magnet and magnetocaloric material, respectively, the cheapest 100 W parallel plate refrigerator with a temperature span of 20 K using Gd and a Halbach magnet has 0.8 kg of magnet, 0.3 kg of Gd and a cost of $35. Using the constant material reduces this cost to $25. A packed sphere bed refrigerator with the constant material costs $7. It is also shown that increasing the operation frequency reduces the cost. Finally, the lowest cost is also found as a function of the cost of the magnet and magnetocaloric material. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100140X [article] Determining the minimum mass and cost of a magnetic refrigerator = Détermination de la masse minimale et du coût d'un réfrigérateur magnétique [texte imprimé] / R. Bjørk, Auteur ; A. Smith, Auteur ; C. R. H. Bahl, Auteur . - 2012 . - pp. 1805–1816. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1805–1816 Mots-clés : Magnetic  refrigerator  Regenerator  Magnetic  fieldModeling Résumé : An expression is determined for the mass of the magnet and magnetocaloric material needed for a magnetic refrigerator and these are determined using numerical modeling for both parallel plate and packed sphere bed regenerators as function of temperature span and cooling power. As magnetocaloric material Gd or a model material with a constant adiabatic temperature change, representing an infinitely linearly graded refrigeration device, is used. For the magnet a maximum figure of merit magnet or a Halbach cylinder is used. For a cost of $40 and $20 per kg for the magnet and magnetocaloric material, respectively, the cheapest 100 W parallel plate refrigerator with a temperature span of 20 K using Gd and a Halbach magnet has 0.8 kg of magnet, 0.3 kg of Gd and a cost of $35. Using the constant material reduces this cost to $25. A packed sphere bed refrigerator with the constant material costs $7. It is also shown that increasing the operation frequency reduces the cost. Finally, the lowest cost is also found as a function of the cost of the magnet and magnetocaloric material. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100140X

Development and experimental results from a 1 kW prototype AMR / C. R. H. Bahl in International journal of refrigeration, Vol. 37 N° 1 (Janvier 2014) 

Public ISBD [article]  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

Experimental and numerical results of a high frequency rotating active magnetic refrigerator / J. A. Lozano in International journal of refrigeration, Vol. 37 N° 1 (Janvier 2014) 

Public ISBD [article]  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

Experimental results for a magnetic refrigerator using three different types of magnetocaloric material regenerators / K. Engelbrecht in International journal of refrigeration, Vol. 34 N° 4 (Juin 2011) 

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Modeling of in-vehicle magnetic refrigeration / U. L. Olsen in International journal of refrigeration, Vol. 37 N° 1 (Janvier 2014) 

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Review and comparison of magnet designs for magnetic refrigeration / R. Bjørk in International journal of refrigeration, Vol. 33 N° 3 (Mai 2010) 

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The influence of non-magnetocaloric properties on the performance in parallel-plate AMRs / K.K. Nielsen in International journal of refrigeration, Vol. 37 N° 1 (Janvier 2014) 

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