Documents disponibles écrits par cet auteur

An experimental study of passive regenerator geometries / K. Engelbrecht 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. 1817–1822 Titre : An experimental study of passive regenerator geometries Titre original : Etude expérimentale sur les géométries des régénérateurs passifs Type de document : texte imprimé Auteurs : K. Engelbrecht, Auteur ; K.K. Nielsen, Auteur ; N. Pryds, Auteur Année de publication : 2012 Article en page(s) : pp. 1817–1822 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Regenerator  Experimentation Résumé : Active magnetic regenerative (AMR) systems are being investigated because they represent a potentially attractive alternative to vapor compression technology. The performance of these systems is dependent on the heat transfer and pressure drop performance of the regenerator geometry. Therefore this article studies the effects of regenerator geometry on performance for flat plate regenerators. This paper investigates methods of improving the performance of flat plate regenerators for use in AMR systems and studies how manufacturing variation affects regenerator performance. In order to eliminate experimental uncertainty associated with magnetocaloric material properties, all regenerators are made of aluminum. The performance of corrugated plates and dimpled plates are compared to traditional flat plate regenerators for a range of cycle times and utilizations. Each regenerator is built using 18 aluminum plates with a 0.4 mm thickness, which allows their performance to be compared directly. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001897 [article] An experimental study of passive regenerator geometries = Etude expérimentale sur les géométries des régénérateurs passifs [texte imprimé] / K. Engelbrecht, Auteur ; K.K. Nielsen, Auteur ; N. Pryds, Auteur . - 2012 . - pp. 1817–1822. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1817–1822 Mots-clés : Magnetic  refrigerator  Regenerator  Experimentation Résumé : Active magnetic regenerative (AMR) systems are being investigated because they represent a potentially attractive alternative to vapor compression technology. The performance of these systems is dependent on the heat transfer and pressure drop performance of the regenerator geometry. Therefore this article studies the effects of regenerator geometry on performance for flat plate regenerators. This paper investigates methods of improving the performance of flat plate regenerators for use in AMR systems and studies how manufacturing variation affects regenerator performance. In order to eliminate experimental uncertainty associated with magnetocaloric material properties, all regenerators are made of aluminum. The performance of corrugated plates and dimpled plates are compared to traditional flat plate regenerators for a range of cycle times and utilizations. Each regenerator is built using 18 aluminum plates with a 0.4 mm thickness, which allows their performance to be compared directly. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001897

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

Experimental investigation of the effect of thermal hysteresis in first order material MnFe(P,As) applied in an AMR device / L. von Moos 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. 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

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) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1132-1140 Titre : Experimental results for a magnetic refrigerator using three different types of magnetocaloric material regenerators Titre original : Résultats expérimentaux obtenus avec un réfrigérateur magnétique utilisant trois types de régénérateurs à matériau magnétocalorique Type de document : texte imprimé Auteurs : K. Engelbrecht, Auteur ; C. R. H. Bahl, Auteur ; K.K. Nielsen, Auteur Année de publication : 2011 Article en page(s) : pp. 1132-1140 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Regenerator  Magnetic  property  Experimentation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Magnetic refrigeration is a potentially environmentally-friendly alternative to vapor compression technology because it has a potentially higher coefficient of performance and does not use a gaseous refrigerant. The active magnetic regenerator refrigerator is currently the most common magnetic refrigeration device for near room temperature applications, and it is driven by the magnetocaloric effect in the regenerator material. Several magnetocaloric materials with potential magnetic refrigeration applications have recently been developed and characterized; however, few of them have been tested in an experimental device. This paper compares the performance of three magnetocaloric material candidates for AMRs, La(Fe,Co,Si)13, (La,Ca,Sr)MnO3 and Gd, in an experimental active magnetic regenerator with a parallel plate geometry. The performance of single-material regenerators of each magnetocaloric material family were compared. In an attempt to improve system performance, graded two-material regenerators were made from two different combinations of La(Fe,Co,Si)13 compounds having different magnetic transition temperatures. One combination of the La(Fe,Co,Si)13 materials yielded a higher performance, while the performance of the other combination was lower than the single-material regenerator. The highest no-load temperature span was achieved by the Gd regenerator. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002823 [article] Experimental results for a magnetic refrigerator using three different types of magnetocaloric material regenerators = Résultats expérimentaux obtenus avec un réfrigérateur magnétique utilisant trois types de régénérateurs à matériau magnétocalorique [texte imprimé] / K. Engelbrecht, Auteur ; C. R. H. Bahl, Auteur ; K.K. Nielsen, Auteur . - 2011 . - pp. 1132-1140. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1132-1140 Mots-clés : Magnetic  refrigerator  Regenerator  Magnetic  property  Experimentation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Magnetic refrigeration is a potentially environmentally-friendly alternative to vapor compression technology because it has a potentially higher coefficient of performance and does not use a gaseous refrigerant. The active magnetic regenerator refrigerator is currently the most common magnetic refrigeration device for near room temperature applications, and it is driven by the magnetocaloric effect in the regenerator material. Several magnetocaloric materials with potential magnetic refrigeration applications have recently been developed and characterized; however, few of them have been tested in an experimental device. This paper compares the performance of three magnetocaloric material candidates for AMRs, La(Fe,Co,Si)13, (La,Ca,Sr)MnO3 and Gd, in an experimental active magnetic regenerator with a parallel plate geometry. The performance of single-material regenerators of each magnetocaloric material family were compared. In an attempt to improve system performance, graded two-material regenerators were made from two different combinations of La(Fe,Co,Si)13 compounds having different magnetic transition temperatures. One combination of the La(Fe,Co,Si)13 materials yielded a higher performance, while the performance of the other combination was lower than the single-material regenerator. The highest no-load temperature span was achieved by the Gd regenerator. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002823

Review on numerical modeling of active magnetic regenerators for room temperature applications / K.K. Nielsen in International journal of refrigeration, Vol. 34 N° 3 (Mai 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 603-616 Titre : Review on numerical modeling of active magnetic regenerators for room temperature applications Titre original : Modélisation numérique des régénérateurs actifs magnétiques pour les applications à température ambiante: synthèse Type de document : texte imprimé Auteurs : K.K. Nielsen, Auteur ; J. Tusek, Auteur ; K. Engelbrecht, Auteur Année de publication : 2011 Article en page(s) : pp. 603-616 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Magnetic  refrigerator  Gadolinium  Regeneration  Modeling Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The active magnetic regenerator (AMR) is an alternative refrigeration cycle with a potential gain of energy efficiency compared to conventional refrigeration techniques. The AMR poses a complex problem of heat transfer, fluid dynamics and magnetic field, which requires detailed and robust modeling. This paper reviews the existing numerical modeling of room temperature AMR to date. The governing equations, implementation of the magnetocaloric effect (MCE), fluid flow and magnetic field profiles, thermal conduction etc. are discussed in detail as is their impact on the AMR cycle. Flow channeling effects, hysteresis, thermal losses and demagnetizing fields are discussed and it is concluded that more detailed modeling of these phenomena is required to obtain a better understanding of the AMR cycle. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000053 [article] Review on numerical modeling of active magnetic regenerators for room temperature applications = Modélisation numérique des régénérateurs actifs magnétiques pour les applications à température ambiante: synthèse [texte imprimé] / K.K. Nielsen, Auteur ; J. Tusek, Auteur ; K. Engelbrecht, Auteur . - 2011 . - pp. 603-616. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 603-616 Mots-clés : Magnetic  refrigerator  Gadolinium  Regeneration  Modeling Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The active magnetic regenerator (AMR) is an alternative refrigeration cycle with a potential gain of energy efficiency compared to conventional refrigeration techniques. The AMR poses a complex problem of heat transfer, fluid dynamics and magnetic field, which requires detailed and robust modeling. This paper reviews the existing numerical modeling of room temperature AMR to date. The governing equations, implementation of the magnetocaloric effect (MCE), fluid flow and magnetic field profiles, thermal conduction etc. are discussed in detail as is their impact on the AMR cycle. Flow channeling effects, hysteresis, thermal losses and demagnetizing fields are discussed and it is concluded that more detailed modeling of these phenomena is required to obtain a better understanding of the AMR cycle. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000053

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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