Documents disponibles écrits par cet auteur

Global modeling of heat and mass transfers in spiral tubular absorber of a water–lithium bromide absorption chiller / Nabil Ben Hafsia in International journal of refrigeration, Vol. 38 (Février 2014) 

Public ISBD [article]  in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 323–332 Titre : Global modeling of heat and mass transfers in spiral tubular absorber of a water–lithium bromide absorption chiller Titre original : Modélisation globale des transferts de chaleur et de masse dans l'absorbeur tubulaire en spirale d'un refroidisseur à bromure de lithium-eau Type de document : texte imprimé Auteurs : Nabil Ben Hafsia, Auteur ; Chaouachi, Bechir, Auteur ; Gabsi, Slimane, Auteur Année de publication : 2014 Article en page(s) : pp. 323–332 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Absorption  chiller;  Linear  and  nonlinear  models;  Transfer  coefficients;  Coupled  transfer;  LMD  method Résumé : In this work, a simplified nonlinear coupled model and a simplified linear coupled model are examined in order to determine the model that better approaches the global mass and heat transfers during water vapor absorption by a falling film of LiBr solution in a spiral tubular absorber of an absorption chiller. The linear coupled model gives up analytical expressions that are used to determine overall heat and mass transfer coefficients from the experimental measurements taken at the inlet and outlet of absorber. These coupled overall transfer coefficients are used with the uncoupled ones that are deduced from the LMD method to determine the simulated absorption parameters along the absorber area. The comparison between the two models based essentially on the different parameters values at the inlet and the outlet of the absorber shows that nonlinear model approaches better experimental results. It shows also that the use of overall coupled transfer coefficients is not significant at low solution flow rates usually encountered in absorption chiller application and therefore the use of the overall transfer coefficients extracted from LMD method approaches well experimental data. The nonlinear model which is the approved model points up that the absorbed water vapor quantity and the overall effective mass transfer coefficient for the spiral tubular absorber increase with decreasing cooling water temperatures. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002739 [article] Global modeling of heat and mass transfers in spiral tubular absorber of a water–lithium bromide absorption chiller = Modélisation globale des transferts de chaleur et de masse dans l'absorbeur tubulaire en spirale d'un refroidisseur à bromure de lithium-eau [texte imprimé] / Nabil Ben Hafsia, Auteur ; Chaouachi, Bechir, Auteur ; Gabsi, Slimane, Auteur . - 2014 . - pp. 323–332. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 323–332 Mots-clés : Absorption  chiller;  Linear  and  nonlinear  models;  Transfer  coefficients;  Coupled  transfer;  LMD  method Résumé : In this work, a simplified nonlinear coupled model and a simplified linear coupled model are examined in order to determine the model that better approaches the global mass and heat transfers during water vapor absorption by a falling film of LiBr solution in a spiral tubular absorber of an absorption chiller. The linear coupled model gives up analytical expressions that are used to determine overall heat and mass transfer coefficients from the experimental measurements taken at the inlet and outlet of absorber. These coupled overall transfer coefficients are used with the uncoupled ones that are deduced from the LMD method to determine the simulated absorption parameters along the absorber area. The comparison between the two models based essentially on the different parameters values at the inlet and the outlet of the absorber shows that nonlinear model approaches better experimental results. It shows also that the use of overall coupled transfer coefficients is not significant at low solution flow rates usually encountered in absorption chiller application and therefore the use of the overall transfer coefficients extracted from LMD method approaches well experimental data. The nonlinear model which is the approved model points up that the absorbed water vapor quantity and the overall effective mass transfer coefficient for the spiral tubular absorber increase with decreasing cooling water temperatures. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002739

Numerical prediction of flow patterns in bubble pumps / Benhmidene, Ali in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Titre : Numerical prediction of flow patterns in bubble pumps Type de document : texte imprimé Auteurs : Benhmidene, Ali, Auteur ; Chaouachi, Bechir, Auteur ; Bourouis, Mahmoud, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Bubble  pump  Flow  pattern  Void  fraction  Simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m−2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m−2, the bubble pump operates under the churn and annular regimes, and the bubble pump performance is improved when the tube diameter increases. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Numerical prediction of flow patterns in bubble pumps [texte imprimé] / Benhmidene, Ali, Auteur ; Chaouachi, Bechir, Auteur ; Bourouis, Mahmoud, Auteur . - 2011 . - 08 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Mots-clés : Bubble  pump  Flow  pattern  Void  fraction  Simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m−2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m−2, the bubble pump operates under the churn and annular regimes, and the bubble pump performance is improved when the tube diameter increases. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]