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Assessment of boiling heat transfer and pressure drop correlations of ammonia/water mixture in a plate heat exchanger / Francisco Táboas in International journal of refrigeration, Vol. 35 N° 3 (Mai 2012) 

Public ISBD [article]  in International journal of refrigeration > Vol. 35 N° 3 (Mai 2012) . - pp. 633–644 Titre : Assessment of boiling heat transfer and pressure drop correlations of ammonia/water mixture in a plate heat exchanger Titre original : Evaluation des corrélations entre le transfert de chaleur lors de l'ébullition et la chute de pression d'un mélange ammoniac / eau dans un échangeur à plaques Type de document : texte imprimé Auteurs : Francisco Táboas, Auteur ; Manel Vallès, Auteur ; Bourouis, Mahmoud, Auteur Année de publication : 2012 Article en page(s) : pp. 633–644 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Absorption  cycle  Boiling  Heat  transfer  Plate  exchanger  Pressure  drop  Ammonia–water Résumé : Plate heat exchangers are gaining acceptance in absorption refrigeration systems due to their high transfer rates, compactness, and low refrigerant charge. Nevertheless, boiling heat transfer and pressure drop studies with mixtures in plate heat exchangers (PHEs) are scarce. In this study, the experimental data of Táboas et al. (2010) on flow boiling of ammonia/water in a plate heat exchanger are compared with the predicted values using the correlations available in the open literature for the boiling heat transfer coefficient and pressure drop. In addition, this study proposes a new correlation based on a separate model by which to obtain the boiling coefficient. The new correlation uses a transition criterion, divided into an apparent nucleate boiling region where pure convective boiling cannot appear, and a region with competition between convective and apparent nucleate boiling. The correlation proposed can predict 98% of data from Táboas et al. (2010) within 20% error. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002477 [article] Assessment of boiling heat transfer and pressure drop correlations of ammonia/water mixture in a plate heat exchanger = Evaluation des corrélations entre le transfert de chaleur lors de l'ébullition et la chute de pression d'un mélange ammoniac / eau dans un échangeur à plaques [texte imprimé] / Francisco Táboas, Auteur ; Manel Vallès, Auteur ; Bourouis, Mahmoud, Auteur . - 2012 . - pp. 633–644. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 35 N° 3 (Mai 2012) . - pp. 633–644 Mots-clés : Absorption  cycle  Boiling  Heat  transfer  Plate  exchanger  Pressure  drop  Ammonia–water Résumé : Plate heat exchangers are gaining acceptance in absorption refrigeration systems due to their high transfer rates, compactness, and low refrigerant charge. Nevertheless, boiling heat transfer and pressure drop studies with mixtures in plate heat exchangers (PHEs) are scarce. In this study, the experimental data of Táboas et al. (2010) on flow boiling of ammonia/water in a plate heat exchanger are compared with the predicted values using the correlations available in the open literature for the boiling heat transfer coefficient and pressure drop. In addition, this study proposes a new correlation based on a separate model by which to obtain the boiling coefficient. The new correlation uses a transition criterion, divided into an apparent nucleate boiling region where pure convective boiling cannot appear, and a region with competition between convective and apparent nucleate boiling. The correlation proposed can predict 98% of data from Táboas et al. (2010) within 20% error. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002477

Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger / Francisco Táboas 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. 695-705 Titre : Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger Titre original : Transfert de chaleur lors de l'ébullition en écoulement d'un mélange d'ammoniac/eau dans un échangeur de chaleur à plaque Type de document : texte imprimé Auteurs : Francisco Táboas, Auteur ; Manel Vallès, Auteur ; Bourouis, Mahmoud, Auteur Année de publication : 2010 Article en page(s) : pp. 695-705 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Absorption  system  Heat  exchanger  Plate  exchanger  Experiment  Heat  transfer  Boiling  Ammonia–water Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The objective of this work is to contribute to the development of plate heat exchangers as desorbers for ammonia/water absorption refrigeration machines driven by waste heat or solar energy. In this study, saturated flow boiling heat transfer and the associated frictional pressure drop of ammonia/water mixture flowing in a vertical plate heat exchanger is experimentally investigated. Experimental data is presented to show the effects of heat flux between 20 and 50 kW m−2, mass flux between 70 and 140 kg m−2 s−1, mean vapour quality from 0.0 to 0.22 and pressure between 7 and 15 bar, for ammonia concentration between 0.42 and 0.62. The results show that for the selected operating conditions, the boiling heat transfer coefficient is highly dependent on the mass flux, whereas the influence of heat flux and pressure are negligible mainly at higher vapour qualities. The pressure drop increases with increasing mass flux and quality. However, the pressure drop is independent of the imposed heat flux. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002825 [article] Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger = Transfert de chaleur lors de l'ébullition en écoulement d'un mélange d'ammoniac/eau dans un échangeur de chaleur à plaque [texte imprimé] / Francisco Táboas, Auteur ; Manel Vallès, Auteur ; Bourouis, Mahmoud, Auteur . - 2010 . - pp. 695-705. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 4 (Juin 2010) . - pp. 695-705 Mots-clés : Absorption  system  Heat  exchanger  Plate  exchanger  Experiment  Heat  transfer  Boiling  Ammonia–water Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The objective of this work is to contribute to the development of plate heat exchangers as desorbers for ammonia/water absorption refrigeration machines driven by waste heat or solar energy. In this study, saturated flow boiling heat transfer and the associated frictional pressure drop of ammonia/water mixture flowing in a vertical plate heat exchanger is experimentally investigated. Experimental data is presented to show the effects of heat flux between 20 and 50 kW m−2, mass flux between 70 and 140 kg m−2 s−1, mean vapour quality from 0.0 to 0.22 and pressure between 7 and 15 bar, for ammonia concentration between 0.42 and 0.62. The results show that for the selected operating conditions, the boiling heat transfer coefficient is highly dependent on the mass flux, whereas the influence of heat flux and pressure are negligible mainly at higher vapour qualities. The pressure drop increases with increasing mass flux and quality. However, the pressure drop is independent of the imposed heat flux. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002825

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 [...]