Documents disponibles écrits par cet auteur

A 2D hybrid model of the fluid flow and heat transfer in a reciprocating active magnetic regenerator / Pablo A. Oliveira in International journal of refrigeration, Vol. 35 N° 1 (Janvier 2012) 

Public ISBD [article]  in International journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 98–114 Titre : A 2D hybrid model of the fluid flow and heat transfer in a reciprocating active magnetic regenerator Titre original : Modèle hybride bidimensionnel pour l'écoulement du fluide et le transfert de chaleur dans un régénérateur actif magnétique alternatif Type de document : texte imprimé Auteurs : Pablo A. Oliveira, Auteur ; Paulo V. Trevizoli, Auteur ; Jader R. Barbosa Jr., Auteur Année de publication : 2012 Article en page(s) : pp. 98–114 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Modelling  Simulation  Regenerator  Magnetic  refrigerator  Cooling  rate  Thermal  analysis Résumé : This paper evaluates the thermal behavior of a magnetic-Brayton-based parallel plate reciprocating active magnetic regenerator (AMR). A time-dependent, 2D model of the fluid flow and the coupled heat transfer between the working fluid and the solid refrigerant (gadolinium) is proposed. A hybrid calculation method which consists of an analytical solution for the flow and a numerical solution for the thermal field has been adopted. Results for the cooling capacity as a function of the temperature span and mass flow rate agree well with trends observed in experimental data and other theoretical models available in the literature. The volume of fluid displaced through the channels during the isofield processes influences significantly the AMR performance. For a cycle frequency of 1 Hz, the cycle-averaged cooling capacity reaches a maximum when the utilization factor is 0.1 and the displaced fluid volume equals 62% of the fluid volume of the AMR. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002118 [article] A 2D hybrid model of the fluid flow and heat transfer in a reciprocating active magnetic regenerator = Modèle hybride bidimensionnel pour l'écoulement du fluide et le transfert de chaleur dans un régénérateur actif magnétique alternatif [texte imprimé] / Pablo A. Oliveira, Auteur ; Paulo V. Trevizoli, Auteur ; Jader R. Barbosa Jr., Auteur . - 2012 . - pp. 98–114. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 98–114 Mots-clés : Modelling  Simulation  Regenerator  Magnetic  refrigerator  Cooling  rate  Thermal  analysis Résumé : This paper evaluates the thermal behavior of a magnetic-Brayton-based parallel plate reciprocating active magnetic regenerator (AMR). A time-dependent, 2D model of the fluid flow and the coupled heat transfer between the working fluid and the solid refrigerant (gadolinium) is proposed. A hybrid calculation method which consists of an analytical solution for the flow and a numerical solution for the thermal field has been adopted. Results for the cooling capacity as a function of the temperature span and mass flow rate agree well with trends observed in experimental data and other theoretical models available in the literature. The volume of fluid displaced through the channels during the isofield processes influences significantly the AMR performance. For a cycle frequency of 1 Hz, the cycle-averaged cooling capacity reaches a maximum when the utilization factor is 0.1 and the displaced fluid volume equals 62% of the fluid volume of the AMR. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002118

Air-side heat transfer and pressure drop characteristics of accelerated flow evaporators / Paulo J. Waltrich in International journal of refrigeration, Vol. 34 N° 2 (Mars 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 2 (Mars 2011) . - pp. 484-497 Titre : Air-side heat transfer and pressure drop characteristics of accelerated flow evaporators Titre original : Evaporateurs à écoulement accéléré: transfert de chaleur côté air et caractéristiques de la chute de pression Type de document : texte imprimé Auteurs : Paulo J. Waltrich, Auteur ; Jader R. Barbosa Jr., Auteur ; Christian J.L. Hermes, Auteur Année de publication : 2011 Article en page(s) : pp. 484-497 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Evaporator  Heat  exchanger  Heat  transfer  coefficient  Enhancement  Household  refrigerator  Modeling  Experimentation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : We investigate an alternative tube-fin evaporator design (accelerated flow evaporator, AFE) in which the air-side local heat transfer coefficient is increased due to a progressive reduction of the free-flow area. For a given heat transfer rate, this enhancement is expected to partially compensate the decrease in surface area, which reduces the evaporator material cost. The air-side thermal-hydraulic behavior of nine AFEs was determined experimentally, and a calculation method that relies on j and f correlations for plain tube-fin heat exchangers and on mass and momentum balances has been proposed. The method enables the calculation of the by-pass fraction associated with the air stream through the clearance between the tube bank and the outer edge of the fins. The agreement between the model, which introduces no additional fitting parameters, and the experiments is within ±10% for all heat transfer data and ±15% for the majority of the pressure drop data. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071000201X [article] Air-side heat transfer and pressure drop characteristics of accelerated flow evaporators = Evaporateurs à écoulement accéléré: transfert de chaleur côté air et caractéristiques de la chute de pression [texte imprimé] / Paulo J. Waltrich, Auteur ; Jader R. Barbosa Jr., Auteur ; Christian J.L. Hermes, Auteur . - 2011 . - pp. 484-497. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 2 (Mars 2011) . - pp. 484-497 Mots-clés : Evaporator  Heat  exchanger  Heat  transfer  coefficient  Enhancement  Household  refrigerator  Modeling  Experimentation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : We investigate an alternative tube-fin evaporator design (accelerated flow evaporator, AFE) in which the air-side local heat transfer coefficient is increased due to a progressive reduction of the free-flow area. For a given heat transfer rate, this enhancement is expected to partially compensate the decrease in surface area, which reduces the evaporator material cost. The air-side thermal-hydraulic behavior of nine AFEs was determined experimentally, and a calculation method that relies on j and f correlations for plain tube-fin heat exchangers and on mass and momentum balances has been proposed. The method enables the calculation of the by-pass fraction associated with the air stream through the clearance between the tube bank and the outer edge of the fins. The agreement between the model, which introduces no additional fitting parameters, and the experiments is within ±10% for all heat transfer data and ±15% for the majority of the pressure drop data. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071000201X

Analytical and CFD modeling of the fluid flow in an eccentric-tube centrifugal oil pump for hermetic compressors / Marcus Vinícius C. Alves in International journal of refrigeration, Vol. 36 N° 7 (Novembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1905–1915 Titre : Analytical and CFD modeling of the fluid flow in an eccentric-tube centrifugal oil pump for hermetic compressors Titre original : Modélisation analytique et à l'aide de la mécanique des fluides numérique de l'écoulement du fluide dans une pompe d'huile centrifuge à tubes excentriques pour les compresseurs hermétiques Type de document : texte imprimé Auteurs : Marcus Vinícius C. Alves, Auteur ; Jader R. Barbosa Jr., Auteur ; Alvaro T. Prata, Auteur Année de publication : 2014 Article en page(s) : pp. 1905–1915 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Reciprocating  compressor;  Lubricant;  Oil;  Pumping;  CFD Résumé : A model is presented for calculating the volume flow rate in an eccentric-tube centrifugal oil pump for reciprocating compressors. The oil pump assembly consists of a pick-up tube with an inclined inlet that is mounted off-center with the crankshaft symmetry axis. The pick-up tube is connected to the shaft channel, a helical groove machined on the crankshaft that facilitates the supply of lubricant to the bearings. The analytical models for the pick-up tube and shaft channel were developed independently and were coupled via a numerical procedure to determine the steady-state volume flow rate in the assembly. The steady-state results were verified against a CFD model, which was also used to evaluate the fluid flow in the oil pump assembly during a start-up transient. A parametric analysis was conducted to quantify the influence of some oil pump geometric parameters, such as the pick-up tube diameter and the shaft eccentricity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712001880 [article] Analytical and CFD modeling of the fluid flow in an eccentric-tube centrifugal oil pump for hermetic compressors = Modélisation analytique et à l'aide de la mécanique des fluides numérique de l'écoulement du fluide dans une pompe d'huile centrifuge à tubes excentriques pour les compresseurs hermétiques [texte imprimé] / Marcus Vinícius C. Alves, Auteur ; Jader R. Barbosa Jr., Auteur ; Alvaro T. Prata, Auteur . - 2014 . - pp. 1905–1915. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1905–1915 Mots-clés : Reciprocating  compressor;  Lubricant;  Oil;  Pumping;  CFD Résumé : A model is presented for calculating the volume flow rate in an eccentric-tube centrifugal oil pump for reciprocating compressors. The oil pump assembly consists of a pick-up tube with an inclined inlet that is mounted off-center with the crankshaft symmetry axis. The pick-up tube is connected to the shaft channel, a helical groove machined on the crankshaft that facilitates the supply of lubricant to the bearings. The analytical models for the pick-up tube and shaft channel were developed independently and were coupled via a numerical procedure to determine the steady-state volume flow rate in the assembly. The steady-state results were verified against a CFD model, which was also used to evaluate the fluid flow in the oil pump assembly during a start-up transient. A parametric analysis was conducted to quantify the influence of some oil pump geometric parameters, such as the pick-up tube diameter and the shaft eccentricity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712001880

A departure-function approach to calculate thermodynamic properties of refrigerant-oil mixtures / Moisés A. Marcelino Neto in International journal of refrigeration, Vol. 36 N° 3 (Mai 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 972–979 Titre : A departure-function approach to calculate thermodynamic properties of refrigerant-oil mixtures Titre original : Approche fondée sur les fonctions pour le calcul des propriétés thermodynamiques des mélanges frigorigène-huile Type de document : texte imprimé Auteurs : Moisés A. Marcelino Neto, Auteur ; Jader R. Barbosa Jr., Auteur Année de publication : 2013 Article en page(s) : pp. 972–979 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Refrigerant;  Oil;  Mixtures;  Phase  equilibrium;  Thermodynamic  properties;  Function Résumé : A method based on the theory of departure functions coupled with the Peng and Robinson (1976) equation of state was used to calculate the thermodynamic properties (internal energy, enthalpy, entropy and specific volume) of refrigerant-oil mixtures. The method is exemplified with isobutane (R-600a)/alkyl benzene ISO 5 and isobutane/polyol ester ISO 7 mixtures. Pressure-enthalpy, pressure–volume and temperature–entropy diagrams are presented for overall oil concentrations ranging from 0.1% to 1%. The influence of the oil type on the working fluid properties is discussed. For a given overall oil concentration, the higher solubility of alkyl benzene ISO 5 (in comparison with polyol ester ISO 7) gives rise to larger deviations from the pure refrigerant behavior. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003477 [article] A departure-function approach to calculate thermodynamic properties of refrigerant-oil mixtures = Approche fondée sur les fonctions pour le calcul des propriétés thermodynamiques des mélanges frigorigène-huile [texte imprimé] / Moisés A. Marcelino Neto, Auteur ; Jader R. Barbosa Jr., Auteur . - 2013 . - pp. 972–979. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 972–979 Mots-clés : Refrigerant;  Oil;  Mixtures;  Phase  equilibrium;  Thermodynamic  properties;  Function Résumé : A method based on the theory of departure functions coupled with the Peng and Robinson (1976) equation of state was used to calculate the thermodynamic properties (internal energy, enthalpy, entropy and specific volume) of refrigerant-oil mixtures. The method is exemplified with isobutane (R-600a)/alkyl benzene ISO 5 and isobutane/polyol ester ISO 7 mixtures. Pressure-enthalpy, pressure–volume and temperature–entropy diagrams are presented for overall oil concentrations ranging from 0.1% to 1%. The influence of the oil type on the working fluid properties is discussed. For a given overall oil concentration, the higher solubility of alkyl benzene ISO 5 (in comparison with polyol ester ISO 7) gives rise to larger deviations from the pure refrigerant behavior. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003477

Experimental evaluation of spray cooling of R-134a on plain and enhanced surfaces / Augusto G. Ulson de Souza in International journal of refrigeration, Vol. 36 N° 2 (N° spécial) (Mars 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 2 (N° spécial) (Mars 2013) . - pp. 527–533 Titre : Experimental evaluation of spray cooling of R-134a on plain and enhanced surfaces Titre original : Evaluation expérimentale de la brumisation du R-134a sur des surfaces planes et augmentées Type de document : texte imprimé Auteurs : Augusto G. Ulson de Souza, Auteur ; Jader R. Barbosa Jr., Auteur Année de publication : 2013 Article en page(s) : pp. 527–533 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Spray  cooling;  Boiling;  Metal  foam;  Heat  transfer  enhancement Résumé : An experimental assessment of the heat transfer coefficient in spray cooling of plain and enhanced upward-facing surfaces is presented. All surfaces of the heater were thermally insulated apart from the top end, onto which pieces with different surface geometries were attached. Average surface temperatures were obtained from four small thermocouples. Three copper surface geometries were evaluated: a plain surface (reference), a 10-pore-per-inch metal foam (90% porosity), and a surface with six 3-mm high 2-mm wide radial grooves. The surface areas of the latter surfaces were 5.1 and 2.2 times larger than that of the plain surface. Boiling curves are presented for increasing heat flux. A base area heat transfer coefficient enhancement factor of 1.35 is obtained for the copper-foam surface, for a coolant flow rate of 3 kg h−1 (8.333 × 10−4 kg s−1). The type of surface geometry is not seen to affect significantly the critical heat flux. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003404 [article] Experimental evaluation of spray cooling of R-134a on plain and enhanced surfaces = Evaluation expérimentale de la brumisation du R-134a sur des surfaces planes et augmentées [texte imprimé] / Augusto G. Ulson de Souza, Auteur ; Jader R. Barbosa Jr., Auteur . - 2013 . - pp. 527–533. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 2 (N° spécial) (Mars 2013) . - pp. 527–533 Mots-clés : Spray  cooling;  Boiling;  Metal  foam;  Heat  transfer  enhancement Résumé : An experimental assessment of the heat transfer coefficient in spray cooling of plain and enhanced upward-facing surfaces is presented. All surfaces of the heater were thermally insulated apart from the top end, onto which pieces with different surface geometries were attached. Average surface temperatures were obtained from four small thermocouples. Three copper surface geometries were evaluated: a plain surface (reference), a 10-pore-per-inch metal foam (90% porosity), and a surface with six 3-mm high 2-mm wide radial grooves. The surface areas of the latter surfaces were 5.1 and 2.2 times larger than that of the plain surface. Boiling curves are presented for increasing heat flux. A base area heat transfer coefficient enhancement factor of 1.35 is obtained for the copper-foam surface, for a coolant flow rate of 3 kg h−1 (8.333 × 10−4 kg s−1). The type of surface geometry is not seen to affect significantly the critical heat flux. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003404

Fluid flow in a screw pump oil supply system for reciprocating compressors / Marcus V. C. Alves in International journal of refrigeration, Vol. 34 N° 1 (Janvier 2011) 

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Modeling the stiction effect in automatic compressor valves / Rodrigo A. Pizarro-Recabarren in International journal of refrigeration, Vol. 36 N° 7 (Novembre 2013) 

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